[001]
The present invention relates to
synthesis and evaluation of intelligent
anticorrosive coatings having superior corrosion resistance, mechanical strength
and thermal stability behavior for metals/
alloys which are exposed to corrosive
5
s
aline environment.
BACKGROUND
AND PRIOR ART
OF INVENTION
[002]
Electrochemical
degradation of metal service life in working conditions is
10
known as corrosion. Co
r
rosion is biggest challenge to the researcher and structural
engineers. Various techniques were
used for the inhibition of corrosion like
anodic protection, cathodic protection and barrier coatings. Intrinsically
conducting polymer was exte
n
sively studied because of their ease of synthesis,
non toxicity, excellent adhesion and good inhibition proper
ties. In recent years
15
many researchers explore the field of corr
o
sion and used the eco
-
friendly fillers
for the inhibition of corrosion. The green fillers materials include plant extracts,
rare earth metals, inorganic compounds and animal byproducts. More
o
ver green
fillers are eco
-
friendly, biodegradable, low cost and environmentally st
a
ble.
Several attempts have been made for developing the eco
-
friendly fillers based
20
anticorrosive coatings. Chitosan can be used as a green filler material because of
its exc
ellent film forming ability and good adhesion prope
r
ties. It is obtained from
exoskeleton of shrimps and crabs. Moreover it’s bio
-
compatible, non
-
toxic and
easily available. Umoren et.al demo
n
strated 96% inhibition efficiency using
chitosan as green inhibi
tor for mild steel in acidic medium. Although for getting
25
high inhibition efficiency, thermal and mechanical stability is still an issue of
concern in aggressive corrosive environment.
[003]
Following are the works done so far in the field of conductive poly
mers
based anti
-
corrosive coatings
30
[004]
US patent
-
6942899 B2:
Coating for inhibiting oxidation of a substrate
3
[005]
The patent relates to coating for inhibiting corrosion of metallic substrate
(aluminum or alloys composed of aluminum) by using conducting polymer w
ith
certain inhibiting ions. Inhibiting ions comprise of
mono
-
thiol, di
-
thiol, poly
-
thiol,
or combinations such as 2,5
-
dimercapto
-
1,3,4
-
thiadiazole; 6
-
ethoxy
-
2
-
mercaptobenzothiazole; 1,3,4 thiadiazole; 6
-
ethoxy
-
2
-
mercaptobenzothiazole,
5
dimethyldithiocarbam
ic acid; o
-
ethylzanthicacid; 2
-
mercaptobenzothiazole; 2
-
mercaptoethanesulfonic acid; diethyldithiocarbamic acid. The coating composed
of cationic electrically conductive carrier (polymer) able to conduct an electric
current and anions of the thiol.
The inv
ention claims when any damage to coating
occurred coating exhibits anticorrosive properties by
releasing anions of the thiol
10
in reducing environment.
[006]
US Patent
5532025 A
:
Corrosion inhibiting compositions
[007]
Present patent relates an anticorrosion coating f
or preventing steel
materials from corrosion by using polyaniline, polypyrrole, blended with binder
materials. The blends exhibit anticorrosive properties in alkaline, acidic and
15
marine environment The present invention provides a corrosion inhibiting blen
ds.
The invention provides a bilayer coating to the substrate. T
he First coating
comprising of intrinsically conducting polymer (polyaniline) blended with
inorganic silicates or organic resins. Secondary coatings is mainly consist
inorganic fillers and org
anic resin. The organic resin is mainly consist of shellac,
20
phenolic resins, alkyd resins, aminoplast resins, epoxy resins, urethane, resins,
acrylic resins, unsaturated polyester resins, vinyl resins, silicones, polyimides,
unsaturated olefin resins, fluo
rinated olefin resins, crosslinkable styrenic regins,
crosslinkable polyamide resins, rubber, elastomer, ionomers, mixture and there
cross linkers.
25
[008]
US Patent
6150032 A:
Electroactive polymer coatings for corrosion
control
[009]
The invention claims synthesis of
anti
-
corrosive polymeric complex which
is comprised of a plurality of double
-
stranded molecular complexes. These
complexes strands were non
-
covalently attached with each other and are soluble
30
in organic solvents. One strand is of conducting polymer like p
olyaniline,
4
polypyrrole, polythiophene, poly(phenylene sulfide), poly(p
-
phenylene) and
poly(phenylene vinylene), and other was copolymer such as of poly(acrylic acid
-
co
-
methylacrylate), poly(acrylic acid
-
co
-
ethylacrylate), poly(acrylic acid
-
co
-
acrylamide),
poly(acrylic acid
-
co
-
methylvinylether) and poly(acrylic acid
-
co
-
ethylvinylether). These complexes were blended with epoxies polyurethanes,
5
polyamides, polyimides, polyaramids, polyacrylates, and poly(vinyl alcohol) and
coated over aluminum and steel subst
rates.
[0010]
US 7294362 B2:
Aqueous
agent
for
treating
substrate
,
method
for
treating
substrate
and
treated
substrate
[0011]
The patent describes preparation of w
ater
-
based, substrate treatment
10
compositions for metal substrates.
The invention claims improvement in the
interlayer adhesion between metal
and
resin coating layers such as films or
coatings,
and
have positive effect on corrosion resistance
and
solvent resistance
properties of metal. Water based compositions mainly consist three
formulations. Formulation (A) c
omposed of chitosan and its derivatives obtained
15
from the following reactions carboxylating, glycolizing, tosylating, sulfating,
phosphatizing, etherifying or alkylating. Formulation (B) is a metal compound
comprises at least one metal from Ti, Zr, Hf, Mo,
W, Se, Ce, Fe, Cu, Zn, V
and
trivalent Cr. Formulation (C) is a organic compound consisting a tribasic,
tetrabasic otr pentabasic acid. This water based coating can be used for the
20
corrosion protection of aluminum, magnesium, copper, iron, zinc, nickel, o
r an
alloy. In typical process metal substrates was treated with the water based
composition followed by drying in a temperature range from 80° C. to 300° C.
[0012]
CN 104277664 A:
Marine anticorrosive coatings
[0013]
The invention relates to a preparation method of
a anticorrosion coating
25
based on epoxy resin, polyurethane, carbon nanotubes, chitosan and fillers etc.
The invention claims the development of anticorrosive coating with high impact
resistance, ease to construct and high service life in marine environment
.
Although epoxies coating have certain good qualities such as good compactness,
rigidity and heat resistance, due to certain short comings it’s unable to meet the
30
service requirements. polyurethane is added to the epoxy to reduce its
5
brittleness, low impa
ct resistance and low adhesion. Polyurethane forms
Semi
-
interpenetrating polymer network structure with epoxies and enhances the
certain properties.
Maleic anhydride added to the composition to reduce the
brittleness of the cured epoxy coating.
Various fil
lers materials
like nano
-
titanium oxide, chitosan, red iron oxide and carbon nanotubes were added to the
5
coating to enhance the surface roughness and contact area of the coating. A
perfect anticorrosive system should have low porosity and uniform coating o
ver
the substrate,
[0014]
CN 102676028 A
:
Long
-
acting waterborne nanometer attapulgite
clay/epoxy anticorrosive coating material and preparing method thereof
10
[0015]
This invention deals with the method of synthesizing
long
-
acting
waterborne
nanometer attapulgite cl
ay/epoxy anticorrosive coating material. The
material is prepared by
the
in
-
situ polymerization of organic modified nanometer
attapulgite clay particles and waterborne epoxy resin. This product further
blended with hardeners, fillers, pigments water and cu
red at 5
-
300 ° C to form
15
anticorrosive coating. Organic modified nanometer attapulgite clay particles
have good compatibility with organic polymer in aqueous system and can easily
be dispersed in oil phase. Nano attapulgite particles have spherical or
sphe
roidal
morphology with diameter in the range of 10
-
300 nm.
The invention claims that
coating posses high mechanical strength, good transparency and weather
20
resistance and excellent construction performance. In comparison with
composition without nanomodifi
ers, coating shows 20
-
40% enhancement in
corrosion protection.
[0016]
JP 2001139875 A:
Aqueous primer coating composition and coated item
[0017]
This
patent describes the anticorrosive coating system developed by graft
25
polymerization of the monomers into the grafted mac
romolecules. The main aim
of the invention is to develop coating with high adhesion, water resistance and
stability of pigment dispersion. The primer coating composed of acid anhydride
-
modified chlorinated polyolefin emulsion resin (A), an aqueous alkyd re
sin (B)
and aqueous novolak epoxy resin (C). In final composition of the aqueous
30
6
coating
(A), (B) and (C) are each 20 to 60 wt. %, 10 to 60 wt.% and 10 to 60
wt.%, respectively.
[0018]
EP 0255102 A1:
Coating compositions containing reactive pigments
and exhibi
ting an excellent resistance to environment attack
[0019]
A excellent anticorrosive coating system is described in present invention.
5
A improved barrier coating system is developed to inhibit the passage of water,
moisture, aggressive corrosive ion into and thro
ugh the coating. Anticorrosive
coating is composed of 8% to about 35% film forming polymers (epoxy,
phenoxy, urethane, vinyl chloride, acrylic, polyester, or alkyd type resin)
,
0 to
about 60% of a corrosion inhibiting agent (metal chromates, metal phosphat
es,
10
metal molybdates, particulate metallic zinc), 3% to about 6% of a plurality of
grades of pyrogenic amorphous silica, 15% to about 55% crystalline silica and
about 0 to 35%, based on the total weight of the composition compatible solvent.
The invention
Claim superior anticorrosion properties of coating and can be used
as primer coatings for aircraft and aerospace vehicles.
15
[0020]
EP 0294013 A2:
Cavitation
-
resistant
polymer
and
coating
[0021]
This invention describes the preparation of cavitation
-
resistant polymer
an
d coating for the metal substrates. The composition contains
24 to 48 wt.% of
a liquid epoxy resin
,
24 to 48 wt.% of a blocked isocyanate prepolymer, 4.2 to
20
12 wt.% of a rheological additive (amorphous silica flatting agent), 1 to 4 wt.%
of a plasticizer
(
dibutyl phthalate
), 10 to 14 wt.% of a curing agent
(
alkyleneamine
) and 0.1 to 0.6 wt.% of a silane (
gamma
-
aminopropyltriethoxysilane
). The formulation contains certain fillers, pigments
and auxiliary agents. The invention claims composition,
polymers,
an
d
coatings
25
provide excellent protection against the
d
eleterious
effects of cavitation.
OBJECT
S
OF THE INVENTION
:
[0022]
The
principal
objective of the present invention is to
deliver a process of
synthesis conjugated copolymers with bio
-
waste like chitosan embe
dded with
30
fillers like nano particles of silica and synthesized in a specific medium.
7
[0023]
Another objective
of this invention is to provide an eco
-
friendly alternative
coating system in place of hazardous materials.
[0024]
Yet another objective is to provide
the su
perior barrier properties,
mechanical strength and excellent adhesion to the substrate.
5
SUMMARY OF THE INVENTION:
[0025]
Briefly, the present invention is about a
polymer coating
for corrosion
protection in marine environment
under aggressive corrosive
condit
ions of 3.5 %
NaCl
or greater, said polymer coating comprising essentially of 0.1 M poly
10
aniline or
0.1
M
poly
anisidine
or both 0.1 M aniline and 0.1 M anisidine
absorbed on silica (SiO
2
) nanoparticles of 150 nm
–
200 nm, optionally added
with 1
-
5 wt. % o
f chitosan.
15
-
30 wt. %, more specifically 20
w
t. %
of silica
nanoparticles
with respect to aniline
or anisidine or aniline
-
co
-
anisidine
monomer
has been added with 1
-
5 wt%, more specifically 1 wt. %
of
chitosan.
15
[0026]
In addition, the present invention disclose
s
a
process of preparation of
polymer coatings for corrosion protection in saline especially marine
environment
through
conducting copolymers of aniline and anisidine
or aniline
or anisidine
in the presence of filler materials
such as
nanoparticles of sili
ca
and
suitable medium
such as
o
-
phosphoric acid and
optionally
bio
-
waste
such as
20
chitosan
.
[0027]
The s
ynthesis of
silica nanoparticles were performed through mixing 1 M
ethanol to 0.1 M
aqueous ammonia solution
wherein further 0.05 M TEOS was
added. A
ppear
ance
of white turbidity confirmed
the formation of SiO
2
nanoparticles
, wherein further said white turbid suspension was centrifuged at
25
1000 rpm,
calcined at 600
°
C for 6 hours
in order to obtain
SiO
2
nanoparticles
of
size
from 150
nm to 200
nm
. 0.1 M aniline or
0.1 M anisidine is adsorbed on
silica nanoparticles of 150
–
200 nm at a
temperature of 50
-
60
o
C
, wherein
further
pre
-
cooled slurry of 0.2 M o
-
phosphoric acid is added
, stirred
for one
hour at
-
5 to 0
o
C
.
0.1
M of ammonium persulfate
wa
s added very slowly dr
op by
30
drop
with continued stirring for
4
-
5 hr
, further filtration of the precipitate using
8
sintered G
-
4 funnel, washing of the product with distilled water until pH
becomes neutral, drying
at 60
-
70
o
C.
0.1
M aniline
or anisidine
was
adsorbed on
silica nanop
articles at 50
-
60
o
C
gone through oxidative polymerization by the
addition of
Ammonium Persulfate
, wherein further 1% chitosan solution in 0.2
M o
-
phosphoric
acid
was added, wherein further 0.1 M a
mmonium persulfate
5
was added dropwise
as
an ox
idant with c
ontinuous stirring,
wherein further
polymerization reaction was carried out
at
-
5 to 0
o
C
.
BRIEF
DESCRIPTION OF DRAWINGS
10
[0028]
Fig.
1:
Schematic of the synthesis of poly(aniline
-
co
-
anisidine)/Chitosan/SiO
2
nano composite by chemical oxidative polymerization
process
[0029]
Fig. 2
:
Tafel plots of epoxy coated mild steel and epoxy with copolymer
15
poly(aniline
-
co
-
anisidine)/Chitosan/SiO
2
nanocomposite coated mild steel
substrate exposed to 3.5 wt.% NaCl solution for 1 day at room temperature in
3.5% NaCl solution.
[0030]
Fig
. 3:
Tafel plots of epoxy coated mild steel and epoxy with copolymer
20
poly(aniline
-
co
-
Anisidine)/
Chitosan/
SiO
2
nanocomposite coated mild steel
substrate exposed to 3.5 wt.% NaCl solution for 15 days at room temperature in
3.5% NaCl solution
[0031]
Fig. 4
:
Tafe
l plots of epoxy coated mild steel and epoxy with copolymer
25
poly(aniline
-
co
-
Anisidine)/Chitosan/SiO
2
nanocomposite coated mild steel
substrate exposed to 3.5 wt.% NaCl solution for 25 day at room temperature in
3.5% NaCl solution
[0032]
Fig. 5:
Photographs of
Composite Epoxy Coated Panels on 1
st
Day after
30
exposure to 5.0 %
NaCl
in Salt Spray Chamber
9
[0033]
Fig. 6
:
Photographs of mild steel panels coated with epoxy after 65 days
exposure to 5.0% NaCl in Salt Spray Chamber as per ASTM
Standards
[0034]
Fig. 7:
Photographs of Copolymer composite epoxy coated mild steel
5
panels of scratch Test(a) Only Epoxy coated mild steel panel (b) 1 % composite
coated panel (c) 2 %
coated panel (d) 3 % coated panel (e) 4 % coated mild steel
panel and (f) 5 %
composite coated mild steel panel
[0035]
Fig. 8:
Test Studies of Epoxy coated panel and copolymer composite
10
panels
[0036]
Fig 9:
SEM micrographs showing morphology of (a), (b), (c) poly
(aniline
-
co
-
Anisidine)/
Chitosan/
SiO
2
at magnification scale & (d) shows Edax
pat
tern
.
SiO
2
particles embedded inside the polymer matrix are visible in the
15
micrograph.
[0037]
Fig
.10:
Photographs of Taber Abrasion Test of (a) epoxy coated (EC) and
epoxy with (b) 1.0% (PACS1), (c) 2.0% (PACS2), (d) 3.0% (PACS3), (e) 4.0%
(PACS4) and (f) 5.0% (
PACS5) loading of poly(aniline
-
co
-
anisidine)/
chitosan/
20
SiO
2
composite coated steel specimens.
DETAILED DESCRIPTION OF THE INVENTION
[0038]
At the very outset of the detailed description, it may be understood that the
25
ensuing description only illustrates a par
ticular form of this invention. However,
such a particular form is only exemplary embodiment, and without intending to
imply any limitation on the scope of this invention. Accordingly, the description
is to be understood as an exemplary embodiment and teac
hing of invention and
not intended to be taken restrictively.
30
10
[0039]
C
oming to the c
orrosion
part
, it should be noted that corrosion
leads to the
degradation of the life span of the materials. Barrier coatings are widely used to
inhibit the corrosion in highly a
ggressive conditions. Herein present invention a
facile in
-
situ chemical oxidative polymerization carried out to synthesize the
polymer composite in aqueous chitosan medium. In typical synthesis 1 wt%
5
chitosan was dissolved in aqueous solution of 0.2 M o
-
p
hosphoric acid. Both the
monomer (aniline 0.1M and anisidine 0.1 M) were adsorbed on the silica
nanopaticles at 60
o
C. The resulting slurry was added in pre cooled solution of
chitosan. Ammonium persulfate
(0.1M)
is used
as a oxidant and added to the
react
ion mixture.
The reaction was stirred for 4
-
5 hours at
-
2
o
C (as shown in
10
figure 1). The resultant mixture was filtered and washed with distilled water till
pH 7 was achieved. The obtained product was dried at
60
-
70
o
C and grinded into
fine powder using mo
rtar and pestle.
[0040]
Barrier anticorrosive coating system is developed by preparing different
formulations of epoxy and copolymer composite. Copolymer composite is
15
blended with epoxy powder in different wt% loadings. The resultant blends were
powder coated o
n the mild steel panels (as shown fig. 5). These panels were
used for electrochemical
analysis;
salt spray analysis and phsico
-
mechanical
analysis (bend test, Taber abrasion test and scratch test).
20
Table 1:
Different electrochemical parameters obtained fr
om Tafel
extrapolation method for the specimens exposed to 3.5% NaCl solution
Tafel Parameters
1
2
5
Exposure days
10
15
20
25
30
BS
β
a (mV/decade)
300.5
38
6
.5
2
4
9.2
239.2
270.5
185.8
237.2
920.1
β
c (mV/decade)
80.3
99.9
87.8
92.9
91
.7
85.2
105.7
235.2
E
corr
(mV)
-
557.7
-
615.5
-
653.5
-
631.5
-
626.8
-
628.7
-
619.1
-
605.7
11
i
corr
(A/cm
2
)
2.1 x10
-
5
4
.2x10
-
5
2.5 x10
-
5
3.
4
x10
-
5
4
.3x10
-
5
3.7 x10
-
5
7.0 x10
-
5
1.
6
x10
-
4
C.R. (mm/year)
0.23
0.
4
9
0.30
0.39
0.50
0.
4
0
0.81
1.9
6
PACS1
β
a (mV/decade)
883.8
139.3
122.7
153.5
171.9
3
4
8.8
182.9
4
32.1
β
c (mV/decade)
4
000.0
19
4
.9
107.9
238.8
4
19.9
4
9
4
.3
4
35.0
523.3
E
corr
(mV)
-
4
57.2
-
6
70.8
-
6
87.0
-
6
29.8
-
5
6
0.1
-
4
35.5
-
6
58.0
-
775.9
i
corr
(A/cm
2
)
3.5x10
-
9
5.3 x10
-
8
1.1 x10
-
7
3
.7 x10
-
7
1.8x10
-
6
4
.2x10
-
8
3.7 x10
-
6
2.8 x10
-
7
C.R. (mm/year)
4
.0x10
-
5
6
.2 x10
-
4
1.3x10
-
3
3.3 x10
-
3
2.1 x10
-
2
4
.9x10
-
4
4
.3x10
-
2
3.2 x10
-
3
% P.E
99.98
98.87
99.56
99.15
95.80
99.87
94.69
99.83
PACS2
β
a (mV/decade)
1950.0
1500.0
1200.0
191.7
183.5
391.8
275.2
272.0
β
c (mV/decade)
1
6
4
.1
13
4
.3
2000.0
215.3
823.5
827.
6
4
70.0
233.5
E
corr
(mV)
-
4
89.7
-
508.5
-
517.7
-
6
05.2
-
6
4
1.2
-
709.9
-
739.9
-
389.5
i
corr
(A/cm
2
)
2.5x10
-
8
7.0 x10
-
8
1.
4
x10
-
7
1.5 x10
-
7
9.8 x10
-
7
1.5 x10
-
8
3.5 x10
-
8
2.0 x10
-
7
C.R. (mm/year)
3.0x10
-
4
8.2x10
-
4
1.7 x10
-
3
1.8 x10
-
3
1.1 x10
-
2
1.8x10
-
4
4
.2x10
-
4
2.3 x10
-
3
% P.E
99.8
6
99.83
99.
4
3
99.5
4
97.80
99.95
99.9
4
99.88
PACS3
β
a (mV/decade)
6
0
4
.2
20
6
.1
112.5
155.2
139.3
------
115.9
193.2
β
c (mV/deca
de)
73.5
87.8
153.5
151.7
275.8
------
319.3
370.1
E
corr
(mV)
-
6
4
5.0
-
729.9
-
751.0
-
717.3
-
700.5
------
-
725.0
-
730.0
i
corr
(A/cm
2
)
12.1x10
-
8
8.3 x10
-
8
1.7 x10
-
7
6
.8x10
-
7
2.3 x10
-
6
------
4
.0x10
-
6
5.9x10
-
6
C.R. (mm/year)
1.3x10
-
3
9.5 x10
-
4
2.0 x10
-
3
7
.9 x10
-
3
2.
6
x10
-
2
------
4
.7x10
-
2
6
.
4
x10
-
2
% P.E
99.
4
3
99.80
99.33
98.23
9
4
.82
------
9
4
.19
9
6
.73
12
PACS4
β
a (mV/decade)
22
4
.2
335.3
225.5
2500.0
151.5
203.3
205.5
133.5
β
c (mV/decade)
102.5
6
22.
6
4
77.5
923.0
1020.0
6
75.5
333.9
193.9
E
corr
(mV)
-
585.8
-
2
6
8.2
-
6
13.5
-
571.2
-
6
33.1
-
6
6
1.0
-
6
39.5
-
6
6
4
.0
i
corr
(A/cm
2
)
4
.7x10
-
9
1.0 x10
-
8
5.1x10
-
8
2.0.x10
-
6
7.9 x10
-
7
2.2.x10
-
6
2.2.x10
-
6
7.3.x10
-
6
C.R. (mm/year)
5.
4
x10
-
5
1.2 x10
-
4
6
.0x10
-
4
2.3x10
-
2
9.2 x10
-
3
2.5x10
-
2
3.9x10
-
2
8.5x10
-
2
%
P.E
99.97
99.97
99.80
9
4
.19
98.1
6
93.75
95.15
95.
6
6
PACS5
β
a (mV/decade)
902.8
27
4
.
4
555.7
328.3
191.9
2080.0
3
6
9.0
350.3
β
c (mV/decade)
1
4
00.0
4
6
0.2
195.7
297.2
271.5
859.5
9
4
3.2
352.7
E
corr
(mV)
-
4
33.3
-
395.5
-
6
12.0
-
39
6
.3
-
6
21.1
-
6
55.5
-
708.9
-
6
37.2
i
corr
(A/cm
2
)
5.3x10
-
8
0.2 x10
-
9
3.
6
x10
-
8
1.0x10
-
8
2.
6
x10
-
7
6
.3 x10
-
8
5.9 x10
-
8
3.7 x10
-
8
C.R. (mm/year)
6
.2x10
-
4
2.7 x10
-
6
4
.2 x10
-
4
1.2x10
-
4
3.0 x10
-
3
7.3 x10
-
4
6
.0x10
-
4
4
.3x10
-
4
% P.E
99.73
99.99
99.8
6
99.9
6
99.
4
0
99.8
1
99.92
99.97
[0041]
The synthesis of silica nanoparticles
may be
carried out by
h
ydrolysis of
tetra
-
ethylorthosilicates (TEOS) in ethanol and ammonia was used as catalyst
.
First ethanol was mixed to aqueous ammonia sol
ution.
D
eionized water was
5
added to this solution mixture and stirred. TEOS was added to this resulting
solution and again stirred at room temperature. The appearance of white
turbidity confirms the formation of SiO
2
nanoparticles. This suspension was
cent
rifuged to obtain silica nanoparticles and further this powder was calcined.
[0042]
Synthesis of polyaniline/
SiO
2
composite was carried out
by taking aniline
10
which was adsorbed on silica nanoparticles. In the above reaction mixture,
pre
-
cooled slurry of
o
-
phosp
horic acid is added. This reaction mixture was then
13
stirred at
-
5 to 0
o
C in a triple walled reactor. In the above reaction mixture,
ammonium persulfate is added very slowly drop by drop. Stirring was continued
stirred for 4
-
5 hr and on completion of polyme
rization, the precipitate is filtered
using sintered funnel. The reaction product was washed thoroughly with distilled
water till the pH of the solution becomes neutral and then precipitate of the
5
polymer composite was dried.
[0043]
Anticorrosive coating was prep
ared by blending obtained polymer
composite with snow white glossy epoxy powder in different weight p
ercent
loading.
The mild steel substrates were cleaned before the coating using
different size of
grade of emery papers of grit size 120, 600, 800
. The pol
ymer/
10
e
poxy mixture is powder coated on mild steel using a electrostatic gun.
The
synthesized copolymer composites were blended with the epoxy resin using a
laboratory ball mill. Several compositions having different wt% proportions of
copolymer composite
with epoxy were prepared. The blended powder coating
formulations were applied on the mild steel surface using an electrostatic spray
15
gun with respect to the substrate. The powder coated mild steel specimens were
cured in an oven for 1 hour.
Coated mild st
eel samples of area 1x1 cm
2
were
used for electrochemical analysis (Tafel Parameters analysis) whereas for salt
spray analysis, mild steel panels were used.
Salt spray analysis was done
according to the ASTM standard. All the coated samples of
specific
dim
ension
20
were placed in salt spray chamber at angle of 15 degree. An intentional cut mark
was given on coated mild steel samples to check their resistance against ambient
conditions.
Salt spray test is performed at a constant temperature with NaCl salt
solu
tion. Salt solution was continuously sprayed in chamber and form mist in
chamber. Temperature and humidity were also maintained throughout the test.
25
All the coated steel panels were exposed to salt spray mist for 60 to120 days.
[0044]
Polyanisidine/
SiO
2
composit
e
were
synthesized by polymerizing anisidine
in aqueous acidic medium of o
-
phosphoric acid. Silica nanoparticles were
adsorbed on monomer anisidine.
A
mmonium persulfate was added to the
reaction mixture very slowly drop by drop. The reaction mixture was
30
c
ontinuously stirred
, and the
resultant product was filtered and washed with
14
distilled water till the pH 7 attained. The obtained product was dried under
vacuum.
[0045]
Prior to powder coating mild steel substrate surface was treated with
different emery papers. T
he resultant polymer composite was blended with
epoxy powder to formulate anticorrosive coating. Several composition
s
having
5
different Wt% loading of polymer composite in epoxy powder was prepared.
Powder coating unit was used to coat blended compositions
on mild steel
substrate. Coated mild steel substrates were used to analyze the anticorrosive
performance of the coating. All electrochemical analysis was carried out in 3.5%
NaCl. Corrosion inhibition performance of polymer composite coatings in
10
aggressive
corrosive conditions was analyzed by salt spray test.
[0046]
Polyaniline/
chitosan/
SiO
2
composite w
ere
prepared by chemical
oxidative polymerization of aniline in presence of o
-
phosphoric acid. First silica
nanoparticles were added to the monomer aniline. The r
esultant mixture was
added to the pre
-
cooled aqueous solution of chitosan in dilute o
-
phosphoric acid.
15
Ammonium persulfate is used as oxidant for the reaction and added to reaction
mixture in drop wise manner. Polymerization reaction mixture was continuous
ly
stirred for 4
-
5 hour. The synthesized polymer composite was filtered with the
help of sintered G
-
2 funnel and washed with distill water till it get neutral pH.
Washing of the composite was carried out to remove excess oxidant and
20
oligomers fr
om the poly
mer composite. The ob
tained residue
s
were further
dried.
[0047]
Corrosion resistant coatings were applied on mild steel substrate by using
electrostatic gun. Ball mill was used to blend the epoxy powder and polymer
composite. These coatings were cured for one hou
r. The resultant coated mild
25
steel substrates were used for electrochemical analysis and salt spray analysis.
[0048]
Polyanisidine
/
chitosan/
SiO
2
composite were
synthesized by a facile
method of
in
situ
oxidative polymerization. Chitosan aqueous solution was
prepared by dissolving chitosan in o
-
phosphoric acid one
(1)
day before the
reaction. Monomer anisidine was encapsulated on silica nanoparticles with
30
continuous stirring. The obtained monomer slurry was added to the pre
-
cooled
15
slurry of chitosan at
-
5 to 0
o
C
and stirred for 2 hours. The aqueous solution
of
ammonium persulfate
was added to the reaction mixture to initiate the
polymerization. The reaction solution was continuously stirred for the 4
-
5 hours
and yields greenish solution. The obtained composite
solution was filtered and
washed with distilled water. The filtered polymer composite was dried in
5
vacuum oven.
[0049]
The resultant dried composite was grind by using mortar & pestle, loaded
in different Wt% in epoxy powder. Coating was fabricated by applying th
ese
powder compositions to mild steel substrates by using powde
r coating unit.
These panels were
cured for one
(1)
hour.
10
[0050]
Polyaniline
-
co
-
o
-
anisidine/
chitosan/
SiO
2
composite were
synthesized by
chemical oxidative copolymerization using ammonium persulfate
as a oxidant in
o
-
phosphoric acid medium. Equimolar concen
tration of monomers aniline and
anisidine
was encapsulated on silica nanoparticles with constant stirring. A pre
-
cooled solution of chitosan was prepared by dissolving 1wt% chitosan in
15
aqueous solut
ion of o
-
phosphoric acid. The monomer mixture was added to the
chitosan slurry and poured in the triple wall reactor. The reaction mixture was
continuously stirred and temperature was maintained at
-
5 to 0
o
C.
The above
solution was polymerized through in
-
s
itu copolymerization by using ammonium
persulphate as a
n
oxidant.
The resultant precipitates was filtered out and washed
20
thoroughly with distill
ed
water. The obtained polymer composite was dried and
grinded into fine powder using mortar and pestle.
[0051]
Anti
corrosive coating system is designed by blending the copolymer
composite with epoxy powder. Various formulations were prepared by loading
different wt% of copolymer composite. Mild steel panels have been used for the
25
sample preparation. Surface of panels w
ere cleaned with acetone and emery
papers. Copolymer/epoxy coating was applied to mild substrates with help of
powder coating unit. These coated mild steel samples were used for all
electrochemical analysis (Tafel analysis). Mild steel substrates with dime
nsion
of 150 x 100 mm were subjected to salt spray analysis. Salt spray analysis is
30
carried out to check anticorrosive performance of the coating. All the
16
experimental conditions were maintained according to ASTM Standards
(ASTMB117).
[0052]
In
typical synthes
is monomers aniline and anisidine were adsorbed on the
Flyash nanoparticles. This solution is added to pre
-
cooled slurry of chitosan in
diluted o
-
phosphoric acid. This reaction mixture was stirred for one
(1)
hour at
-
5
5 to 0
o
C.
A
mmonium persulfate oxidant
is dissolved in 0.2 ltr of distilled water
and added to reaction mixture in drop wise manner. The reaction mixture is
stirred for 4
-
5 hr and filtered using G
-
2 filtration funnel. The reaction product
was washed thoroughly with distilled water and dried.
[0053]
Th
e
obtained composite was ball milled with epoxy powder for the
10
formulation of corrosion resistant coatings. Cleaned mild steel substrates were
coated with these formulations and cured
for one
(1)
hour. These coated panels
were used for Tafel analysis as we
ll as salt spray analysis.
Bend test was carried
out to check the adhes
ion of coating to the substrate and to examine
for any
visible crack in the coating.
15
Embodiments:
[0054]
In one embodiment of the invention, the monomers selected for study are
aniline and an
isidine.
In another embodiment of the invention, bio
-
waste chitosan is dissolved in the
reaction medium.
20
In another embodiment of the invention, the filler material like silica nano
particles has been used for the polymerization.
In another embodiment of
the invention, the reaction medium for polymerization
is selected from phosphoric acid and the like.
[0055]
In
another embodiment of the invention, the oxidant such as ammonium
25
persulphate or potassium persulphate, ferric chloride and the like has been used.
In a
nother embodiment of the invention, the polymerization reaction condition
was maintained at 0 to 5
o
C temperature.
[0056]
In further embodiment of the invention, the loading of filler material in the
polymeric matrix with respect to monomer was kept between 1 to
25 %.
30

Claims:We Claim:

1. A polymer coating for corrosion protection in marine environment under aggressive corrosive conditions of 3.5 % NaCl or greater, said polymer coating comprising essentially of 0.1 M poly aniline or 0.1 M poly anisidine or both 0.1 M aniline and 0.1 M anisidine absorbed on silica (SiO2) nanoparticles of 150 nm – 200 nm, optionally added with 1-5 wt. % of chitosan.

2. The polymer coating as claimed in claim 1, wherein 15-30 wt. %, more specifically 20 wt. % of silica nanoparticles with respect to aniline monomer has been added with 1-5 wt%, more specifically 1 wt. % of chitosan.

3. The polymer coating as claimed in claim 1, wherein 15-30 wt. %, more specifically 20 wt. % of silica nanoparticles with respect to anisidine monomer has been added with 1-5 wt%, more specifically 1 wt. % of chitosan.

4. The polymer coating as claimed in claim 1, wherein 15-30 wt. %, more specifically 20 wt. % of silica nanoparticles with respect to aniline-co-anisidine has been added with 1-5 wt% of chitosan.

5. A process of preparation of polymer coatings for corrosion protection in saline especially marine environment through conducting copolymers of aniline and anisidine or aniline or anisidine in the presence of filler materials such as nanoparticles of silica and suitable medium such as o-phosphoric acid and optionally bio-waste such as chitosan.

6. The process as claimed in claim 5, wherein synthesis of silica nanoparticles were performed through mixing 1 M ethanol to 0.1 M aqueous ammonia solution wherein further 0.05 M TEOS was added.
7. The process as claimed in claim 5, wherein appearance of white turbidity confirmed the formation of SiO2 nanoparticles, wherein further said white turbid suspension was centrifuged at 1000 rpm, calcined at 600?C for 6 hours in order to obtain SiO2 nanoparticles of size from 150 nm to 200 nm.

8. The process as claimed in claim 5, wherein 0.1 M aniline or 0.1 M anisidine is adsorbed on silica nanoparticles of 150 – 200 nm at a temperature of 50-60oC, wherein further pre-cooled slurry of 0.2 M o-phosphoric acid is added, stirred for one hour at -5 to 0oC.

9. The process as claimed in claim 8, wherein 0.1 M of ammonium persulfate was added very slowly drop by drop with continued stirring for 4-5 hr, further filtration of the precipitate using sintered G-4 funnel, washing of the product with distilled water until pH becomes neutral, drying at 60-70 o C.

10. The process as claimed in claim 5, wherein 0.1 M aniline or anisidine adsorbed on silica nanoparticles at 50-60 o C was gone through oxidative polymerization by 0.1 M Ammonium Persulfate, wherein further 1% chitosan solution in 0.2 M o-phosphoric acid was added.

11. The process as claimed in claim 10, wherein 0.1 M ammonium persulfate was added dropwise as an oxidant with continuous stirring, wherein further polymerization reaction was carried out at - 5 to 0 o C.
, Description:FIELD OF INVENTION

[001] The present invention relates to synthesis and evaluation of intelligent anticorrosive coatings having superior corrosion resistance, mechanical strength and thermal stability behavior for metals/ alloys which are exposed to corrosive saline environment.

BACKGROUND AND PRIOR ART OF INVENTION

[002] Electrochemical degradation of metal service life in working conditions is known as corrosion. Corrosion is biggest challenge to the researcher and structural engineers. Various techniques were used for the inhibition of corrosion like anodic protection, cathodic protection and barrier coatings. Intrinsically conducting polymer was extensively studied because of their ease of synthesis, non toxicity, excellent adhesion and good inhibition properties. In recent years many researchers explore the field of corrosion and used the eco-friendly fillers for the inhibition of corrosion. The green fillers materials include plant extracts, rare earth metals, inorganic compounds and animal byproducts. Moreover green fillers are eco-friendly, biodegradable, low cost and environmentally stable. Several attempts have been made for developing the eco-friendly fillers based anticorrosive coatings. Chitosan can be used as a green filler material because of its excellent film forming ability and good adhesion properties. It is obtained from exoskeleton of shrimps and crabs. Moreover it’s bio-compatible, non-toxic and easily available. Umoren et.al demonstrated 96% inhibition efficiency using chitosan as green inhibitor for mild steel in acidic medium. Although for getting high inhibition efficiency, thermal and mechanical stability is still an issue of concern in aggressive corrosive environment.

[003] Following are the works done so far in the field of conductive polymers based anti -corrosive coatings
[004] US patent- 6942899 B2: Coating for inhibiting oxidation of a substrate
[005] The patent relates to coating for inhibiting corrosion of metallic substrate (aluminum or alloys composed of aluminum) by using conducting polymer with certain inhibiting ions. Inhibiting ions comprise of mono-thiol, di-thiol, poly-thiol, or combinations such as 2,5-dimercapto-1,3,4-thiadiazole; 6-ethoxy-2-mercaptobenzothiazole; 1,3,4 thiadiazole; 6-ethoxy-2-mercaptobenzothiazole, dimethyldithiocarbamic acid; o-ethylzanthicacid; 2-mercaptobenzothiazole; 2-mercaptoethanesulfonic acid; diethyldithiocarbamic acid. The coating composed of cationic electrically conductive carrier (polymer) able to conduct an electric current and anions of the thiol. The invention claims when any damage to coating occurred coating exhibits anticorrosive properties by releasing anions of the thiol in reducing environment.
[006] US Patent 5532025 A: Corrosion inhibiting compositions
[007] Present patent relates an anticorrosion coating for preventing steel materials from corrosion by using polyaniline, polypyrrole, blended with binder materials. The blends exhibit anticorrosive properties in alkaline, acidic and marine environment The present invention provides a corrosion inhibiting blends. The invention provides a bilayer coating to the substrate. The First coating comprising of intrinsically conducting polymer (polyaniline) blended with inorganic silicates or organic resins. Secondary coatings is mainly consist inorganic fillers and organic resin. The organic resin is mainly consist of shellac, phenolic resins, alkyd resins, aminoplast resins, epoxy resins, urethane, resins, acrylic resins, unsaturated polyester resins, vinyl resins, silicones, polyimides, unsaturated olefin resins, fluorinated olefin resins, crosslinkable styrenic regins, crosslinkable polyamide resins, rubber, elastomer, ionomers, mixture and there cross linkers.
[008] US Patent 6150032 A: Electroactive polymer coatings for corrosion control
[009] The invention claims synthesis of anti-corrosive polymeric complex which is comprised of a plurality of double-stranded molecular complexes. These complexes strands were non-covalently attached with each other and are soluble in organic solvents. One strand is of conducting polymer like polyaniline, polypyrrole, polythiophene, poly(phenylene sulfide), poly(p-phenylene) and poly(phenylene vinylene), and other was copolymer such as of poly(acrylic acid-co-methylacrylate), poly(acrylic acid-co-ethylacrylate), poly(acrylic acid-co-acrylamide), poly(acrylic acid-co-methylvinylether) and poly(acrylic acid-co-ethylvinylether). These complexes were blended with epoxies polyurethanes, polyamides, polyimides, polyaramids, polyacrylates, and poly(vinyl alcohol) and coated over aluminum and steel substrates.
[0010] US 7294362 B2: Aqueous agent for treating substrate, method for treating substrate and treated substrate
[0011] The patent describes preparation of water-based, substrate treatment compositions for metal substrates. The invention claims improvement in the interlayer adhesion between metal and resin coating layers such as films or coatings, and have positive effect on corrosion resistance and solvent resistance properties of metal. Water based compositions mainly consist three formulations. Formulation (A) composed of chitosan and its derivatives obtained from the following reactions carboxylating, glycolizing, tosylating, sulfating, phosphatizing, etherifying or alkylating. Formulation (B) is a metal compound comprises at least one metal from Ti, Zr, Hf, Mo, W, Se, Ce, Fe, Cu, Zn, V and trivalent Cr. Formulation (C) is a organic compound consisting a tribasic, tetrabasic otr pentabasic acid. This water based coating can be used for the corrosion protection of aluminum, magnesium, copper, iron, zinc, nickel, or an alloy. In typical process metal substrates was treated with the water based composition followed by drying in a temperature range from 80° C. to 300° C.
[0012] CN 104277664 A: Marine anticorrosive coatings
[0013] The invention relates to a preparation method of a anticorrosion coating based on epoxy resin, polyurethane, carbon nanotubes, chitosan and fillers etc. The invention claims the development of anticorrosive coating with high impact resistance, ease to construct and high service life in marine environment. Although epoxies coating have certain good qualities such as good compactness, rigidity and heat resistance, due to certain short comings it’s unable to meet the service requirements. polyurethane is added to the epoxy to reduce its brittleness, low impact resistance and low adhesion. Polyurethane forms Semi-interpenetrating polymer network structure with epoxies and enhances the certain properties. Maleic anhydride added to the composition to reduce the brittleness of the cured epoxy coating. Various fillers materials like nano-titanium oxide, chitosan, red iron oxide and carbon nanotubes were added to the coating to enhance the surface roughness and contact area of the coating. A perfect anticorrosive system should have low porosity and uniform coating over the substrate,
[0014] CN 102676028 A: Long-acting waterborne nanometer attapulgite clay/epoxy anticorrosive coating material and preparing method thereof
[0015] This invention deals with the method of synthesizing long-acting waterborne nanometer attapulgite clay/epoxy anticorrosive coating material. The material is prepared by the in-situ polymerization of organic modified nanometer attapulgite clay particles and waterborne epoxy resin. This product further blended with hardeners, fillers, pigments water and cured at 5-300 ° C to form anticorrosive coating. Organic modified nanometer attapulgite clay particles have good compatibility with organic polymer in aqueous system and can easily be dispersed in oil phase. Nano attapulgite particles have spherical or spheroidal morphology with diameter in the range of 10-300 nm. The invention claims that coating posses high mechanical strength, good transparency and weather resistance and excellent construction performance. In comparison with composition without nanomodifiers, coating shows 20-40% enhancement in corrosion protection.
[0016] JP 2001139875 A: Aqueous primer coating composition and coated item
[0017] This patent describes the anticorrosive coating system developed by graft polymerization of the monomers into the grafted macromolecules. The main aim of the invention is to develop coating with high adhesion, water resistance and stability of pigment dispersion. The primer coating composed of acid anhydride-modified chlorinated polyolefin emulsion resin (A), an aqueous alkyd resin (B) and aqueous novolak epoxy resin (C). In final composition of the aqueous coating (A), (B) and (C) are each 20 to 60 wt. %, 10 to 60 wt.% and 10 to 60 wt.%, respectively.
[0018] EP 0255102 A1: Coating compositions containing reactive pigments and exhibiting an excellent resistance to environment attack
[0019] A excellent anticorrosive coating system is described in present invention. A improved barrier coating system is developed to inhibit the passage of water, moisture, aggressive corrosive ion into and through the coating. Anticorrosive coating is composed of 8% to about 35% film forming polymers (epoxy, phenoxy, urethane, vinyl chloride, acrylic, polyester, or alkyd type resin), 0 to about 60% of a corrosion inhibiting agent (metal chromates, metal phosphates, metal molybdates, particulate metallic zinc), 3% to about 6% of a plurality of grades of pyrogenic amorphous silica, 15% to about 55% crystalline silica and about 0 to 35%, based on the total weight of the composition compatible solvent. The invention Claim superior anticorrosion properties of coating and can be used as primer coatings for aircraft and aerospace vehicles.
[0020] EP 0294013 A2: Cavitation-resistant polymer and coating

[0021] This invention describes the preparation of cavitation-resistant polymer and coating for the metal substrates. The composition contains 24 to 48 wt.% of a liquid epoxy resin, 24 to 48 wt.% of a blocked isocyanate prepolymer, 4.2 to 12 wt.% of a rheological additive (amorphous silica flatting agent), 1 to 4 wt.% of a plasticizer (dibutyl phthalate), 10 to 14 wt.% of a curing agent (alkyleneamine) and 0.1 to 0.6 wt.% of a silane (gamma-aminopropyltriethoxysilane). The formulation contains certain fillers, pigments and auxiliary agents. The invention claims composition, polymers, and coatings provide excellent protection against the deleterious effects of cavitation.

OBJECTS OF THE INVENTION:
[0022] The principal objective of the present invention is to deliver a process of synthesis conjugated copolymers with bio-waste like chitosan embedded with fillers like nano particles of silica and synthesized in a specific medium.
[0023] Another objective of this invention is to provide an eco-friendly alternative coating system in place of hazardous materials.
[0024] Yet another objective is to provide the superior barrier properties, mechanical strength and excellent adhesion to the substrate.

SUMMARY OF THE INVENTION:

[0025] Briefly, the present invention is about a polymer coating for corrosion protection in marine environment under aggressive corrosive conditions of 3.5 % NaCl or greater, said polymer coating comprising essentially of 0.1 M poly aniline or 0.1 M poly anisidine or both 0.1 M aniline and 0.1 M anisidine absorbed on silica (SiO2) nanoparticles of 150 nm – 200 nm, optionally added with 1-5 wt. % of chitosan. 15-30 wt. %, more specifically 20 wt. % of silica nanoparticles with respect to aniline or anisidine or aniline-co-anisidine monomer has been added with 1-5 wt%, more specifically 1 wt. % of chitosan.
[0026] In addition, the present invention discloses a process of preparation of polymer coatings for corrosion protection in saline especially marine environment through conducting copolymers of aniline and anisidine or aniline or anisidine in the presence of filler materials such as nanoparticles of silica and suitable medium such as o-phosphoric acid and optionally bio-waste such as chitosan.
[0027] The synthesis of silica nanoparticles were performed through mixing 1 M ethanol to 0.1 M aqueous ammonia solution wherein further 0.05 M TEOS was added. Appearance of white turbidity confirmed the formation of SiO2 nanoparticles, wherein further said white turbid suspension was centrifuged at 1000 rpm, calcined at 600?C for 6 hours in order to obtain SiO2 nanoparticles of size from 150 nm to 200 nm. 0.1 M aniline or 0.1 M anisidine is adsorbed on silica nanoparticles of 150 – 200 nm at a temperature of 50-60oC, wherein further pre-cooled slurry of 0.2 M o-phosphoric acid is added, stirred for one hour at -5 to 0oC. 0.1 M of ammonium persulfate was added very slowly drop by drop with continued stirring for 4-5 hr, further filtration of the precipitate using sintered G-4 funnel, washing of the product with distilled water until pH becomes neutral, drying at 60-70oC. 0.1 M aniline or anisidine was adsorbed on silica nanoparticles at 50-60 o C gone through oxidative polymerization by the addition of Ammonium Persulfate, wherein further 1% chitosan solution in 0.2 M o-phosphoric acid was added, wherein further 0.1 M ammonium persulfate was added dropwise as an oxidant with continuous stirring, wherein further polymerization reaction was carried out at - 5 to 0oC.

BRIEF DESCRIPTION OF DRAWINGS

[0028] Fig. 1: Schematic of the synthesis of poly(aniline-co-anisidine)/Chitosan/SiO2 nano composite by chemical oxidative polymerization process

[0029] Fig. 2: Tafel plots of epoxy coated mild steel and epoxy with copolymer poly(aniline-co-anisidine)/Chitosan/SiO2 nanocomposite coated mild steel substrate exposed to 3.5 wt.% NaCl solution for 1 day at room temperature in 3.5% NaCl solution.

[0030] Fig. 3: Tafel plots of epoxy coated mild steel and epoxy with copolymer poly(aniline-co-Anisidine)/ Chitosan/ SiO2 nanocomposite coated mild steel substrate exposed to 3.5 wt.% NaCl solution for 15 days at room temperature in 3.5% NaCl solution

[0031] Fig. 4: Tafel plots of epoxy coated mild steel and epoxy with copolymer poly(aniline-co-Anisidine)/Chitosan/SiO2 nanocomposite coated mild steel substrate exposed to 3.5 wt.% NaCl solution for 25 day at room temperature in 3.5% NaCl solution

[0032] Fig. 5: Photographs of Composite Epoxy Coated Panels on 1st Day after exposure to 5.0 % NaCl in Salt Spray Chamber

[0033] Fig. 6: Photographs of mild steel panels coated with epoxy after 65 days exposure to 5.0% NaCl in Salt Spray Chamber as per ASTM Standards

[0034] Fig. 7: Photographs of Copolymer composite epoxy coated mild steel panels of scratch Test(a) Only Epoxy coated mild steel panel (b) 1 % composite coated panel (c) 2 % coated panel (d) 3 % coated panel (e) 4 % coated mild steel panel and (f) 5 % composite coated mild steel panel

[0035] Fig. 8: Test Studies of Epoxy coated panel and copolymer composite panels

[0036] Fig 9: SEM micrographs showing morphology of (a), (b), (c) poly (aniline-co-Anisidine)/ Chitosan/ SiO2 at magnification scale & (d) shows Edax pattern. SiO2 particles embedded inside the polymer matrix are visible in the micrograph.

[0037] Fig.10: Photographs of Taber Abrasion Test of (a) epoxy coated (EC) and epoxy with (b) 1.0% (PACS1), (c) 2.0% (PACS2), (d) 3.0% (PACS3), (e) 4.0% (PACS4) and (f) 5.0% (PACS5) loading of poly(aniline-co-anisidine)/ chitosan/ SiO2 composite coated steel specimens.

DETAILED DESCRIPTION OF THE INVENTION

[0038] At the very outset of the detailed description, it may be understood that the ensuing description only illustrates a particular form of this invention. However, such a particular form is only exemplary embodiment, and without intending to imply any limitation on the scope of this invention. Accordingly, the description is to be understood as an exemplary embodiment and teaching of invention and not intended to be taken restrictively.
[0039] Coming to the corrosion part, it should be noted that corrosion leads to the degradation of the life span of the materials. Barrier coatings are widely used to inhibit the corrosion in highly aggressive conditions. Herein present invention a facile in-situ chemical oxidative polymerization carried out to synthesize the polymer composite in aqueous chitosan medium. In typical synthesis 1 wt% chitosan was dissolved in aqueous solution of 0.2 M o-phosphoric acid. Both the monomer (aniline 0.1M and anisidine 0.1 M) were adsorbed on the silica nanopaticles at 60 oC. The resulting slurry was added in pre cooled solution of chitosan. Ammonium persulfate (0.1M) is used as a oxidant and added to the reaction mixture. The reaction was stirred for 4-5 hours at -2 oC (as shown in figure 1). The resultant mixture was filtered and washed with distilled water till pH 7 was achieved. The obtained product was dried at 60-70 oC and grinded into fine powder using mortar and pestle.
[0040] Barrier anticorrosive coating system is developed by preparing different formulations of epoxy and copolymer composite. Copolymer composite is blended with epoxy powder in different wt% loadings. The resultant blends were powder coated on the mild steel panels (as shown fig. 5). These panels were used for electrochemical analysis; salt spray analysis and phsico-mechanical analysis (bend test, Taber abrasion test and scratch test).

Table 1: Different electrochemical parameters obtained from Tafel extrapolation method for the specimens exposed to 3.5% NaCl solution

Tafel Parameters
1

2
5 Exposure days

10
15
20
25
30
BS
?a (mV/decade) 300.5 38?.5 2?9.2 239.2 270.5 185.8 237.2 920.1
?c (mV/decade) 80.3 99.9 87.8 92.9 91.7 85.2 105.7 235.2
Ecorr (mV) -557.7 -615.5 -653.5 -631.5 -626.8 -628.7 -619.1 -605.7
icorr (A/cm2) 2.1 x10-5 ?.2x10-5 2.5 x10-5 3.? x10-5 ?.3x10-5 3.7 x10-5 7.0 x10-5 1.? x10-?
C.R. (mm/year) 0.23 0.?9 0.30 0.39 0.50 0.?0 0.81 1.9?

PACS1
?a (mV/decade) 883.8 139.3 122.7 153.5 171.9 3?8.8 182.9 ?32.1
?c (mV/decade) ?000.0 19?.9 107.9 238.8 ?19.9 ?9?.3 ?35.0 523.3
Ecorr (mV) -?57.2 -?70.8 -?87.0 -?29.8 -5?0.1 -?35.5 -?58.0 -775.9

icorr (A/cm2) 3.5x10-9 5.3 x10-8 1.1 x10-7 3.7 x10-7 1.8x10-? ?.2x10-8 3.7 x10-? 2.8 x10-7
C.R. (mm/year) ?.0x10-5 ?.2 x10-? 1.3x10-3 3.3 x10-3 2.1 x10-2 ?.9x10-? ?.3x10-2 3.2 x10-3
% P.E 99.98 98.87 99.56 99.15 95.80 99.87 94.69 99.83
PACS2
?a (mV/decade) 1950.0 1500.0 1200.0 191.7 183.5 391.8 275.2 272.0
?c (mV/decade) 1??.1 13?.3 2000.0 215.3 823.5 827.? ?70.0 233.5
Ecorr (mV) -?89.7 -508.5 -517.7 -?05.2 -??1.2 -709.9 -739.9 -389.5
icorr (A/cm2) 2.5x10-8 7.0 x10-8 1.? x10-7 1.5 x10-7 9.8 x10-7 1.5 x10-8 3.5 x10-8 2.0 x10-7
C.R. (mm/year) 3.0x10-? 8.2x10-? 1.7 x10-3 1.8 x10-3 1.1 x10-2 1.8x10-? ?.2x10-? 2.3 x10-3
% P.E 99.8? 99.83 99.?3 99.5? 97.80 99.95 99.9? 99.88
PACS3
?a (mV/decade) ?0?.2 20?.1 112.5 155.2 139.3 ------ 115.9 193.2
?c (mV/decade) 73.5 87.8 153.5 151.7 275.8 ------ 319.3 370.1
Ecorr (mV) -??5.0 -729.9 -751.0 -717.3 -700.5 ------ -725.0 -730.0
icorr (A/cm2) 12.1x10-8 8.3 x10-8 1.7 x10-7 ?.8x10-7 2.3 x10-? ------ ?.0x10-? 5.9x10-?
C.R. (mm/year) 1.3x10-3 9.5 x10-? 2.0 x10-3 7.9 x10-3 2.? x10-2 ------ ?.7x10-2 ?.?x10-2
% P.E 99.?3 99.80 99.33 98.23 9?.82 ------ 9?.19 9?.73
PACS4
?a (mV/decade) 22?.2 335.3 225.5 2500.0 151.5 203.3 205.5 133.5
?c (mV/decade) 102.5 ?22.? ?77.5 923.0 1020.0 ?75.5 333.9 193.9
Ecorr (mV) -585.8 -2?8.2 -?13.5 -571.2 -?33.1 -??1.0 -?39.5 -???.0
icorr (A/cm2) ?.7x10-9 1.0 x10-8 5.1x10-8 2.0.x10-? 7.9 x10-7 2.2.x10-? 2.2.x10-? 7.3.x10-?
C.R. (mm/year) 5.?x10-5 1.2 x10-? ?.0x10-? 2.3x10-2 9.2 x10-3 2.5x10-2 3.9x10-2 8.5x10-2
% P.E 99.97 99.97 99.80 9?.19 98.1? 93.75 95.15 95.??
PACS5
?a (mV/decade) 902.8 27?.? 555.7 328.3 191.9 2080.0 3?9.0 350.3
?c (mV/decade) 1?00.0 ??0.2 195.7 297.2 271.5 859.5 9?3.2 352.7
Ecorr (mV) -?33.3 -395.5 -?12.0 -39?.3 -?21.1 -?55.5 -708.9 -?37.2
icorr (A/cm2) 5.3x10-8 0.2 x10-9 3.?x10-8 1.0x10-8 2.? x10-7 ?.3 x10-8 5.9 x10-8 3.7 x10-8
C.R. (mm/year) ?.2x10-? 2.7 x10-? ?.2 x10-? 1.2x10-? 3.0 x10-3 7.3 x10-? ?.0x10-? ?.3x10-?
% P.E 99.73 99.99
99.99 99.8? 99.9? 99.?0 99.81 99.92 99.97

[0041] The synthesis of silica nanoparticles may be carried out by hydrolysis of tetra-ethylorthosilicates (TEOS) in ethanol and ammonia was used as catalyst. First ethanol was mixed to aqueous ammonia solution. Deionized water was added to this solution mixture and stirred. TEOS was added to this resulting solution and again stirred at room temperature. The appearance of white turbidity confirms the formation of SiO2 nanoparticles. This suspension was centrifuged to obtain silica nanoparticles and further this powder was calcined.
[0042] Synthesis of polyaniline/ SiO2 composite was carried out by taking aniline which was adsorbed on silica nanoparticles. In the above reaction mixture, pre-cooled slurry of o-phosphoric acid is added. This reaction mixture was then stirred at -5 to 0oC in a triple walled reactor. In the above reaction mixture, ammonium persulfate is added very slowly drop by drop. Stirring was continued stirred for 4-5 hr and on completion of polymerization, the precipitate is filtered using sintered funnel. The reaction product was washed thoroughly with distilled water till the pH of the solution becomes neutral and then precipitate of the polymer composite was dried.
[0043] Anticorrosive coating was prepared by blending obtained polymer composite with snow white glossy epoxy powder in different weight percent loading. The mild steel substrates were cleaned before the coating using different size of grade of emery papers of grit size 120, 600, 800. The polymer/ epoxy mixture is powder coated on mild steel using a electrostatic gun. The synthesized copolymer composites were blended with the epoxy resin using a laboratory ball mill. Several compositions having different wt% proportions of copolymer composite with epoxy were prepared. The blended powder coating formulations were applied on the mild steel surface using an electrostatic spray gun with respect to the substrate. The powder coated mild steel specimens were cured in an oven for 1 hour. Coated mild steel samples of area 1x1 cm2 were used for electrochemical analysis (Tafel Parameters analysis) whereas for salt spray analysis, mild steel panels were used. Salt spray analysis was done according to the ASTM standard. All the coated samples of specific dimension were placed in salt spray chamber at angle of 15 degree. An intentional cut mark was given on coated mild steel samples to check their resistance against ambient conditions. Salt spray test is performed at a constant temperature with NaCl salt solution. Salt solution was continuously sprayed in chamber and form mist in chamber. Temperature and humidity were also maintained throughout the test. All the coated steel panels were exposed to salt spray mist for 60 to120 days.
[0044] Polyanisidine/ SiO2 composite were synthesized by polymerizing anisidine in aqueous acidic medium of o-phosphoric acid. Silica nanoparticles were adsorbed on monomer anisidine. Ammonium persulfate was added to the reaction mixture very slowly drop by drop. The reaction mixture was continuously stirred, and the resultant product was filtered and washed with distilled water till the pH 7 attained. The obtained product was dried under vacuum.
[0045] Prior to powder coating mild steel substrate surface was treated with different emery papers. The resultant polymer composite was blended with epoxy powder to formulate anticorrosive coating. Several compositions having different Wt% loading of polymer composite in epoxy powder was prepared. Powder coating unit was used to coat blended compositions on mild steel substrate. Coated mild steel substrates were used to analyze the anticorrosive performance of the coating. All electrochemical analysis was carried out in 3.5% NaCl. Corrosion inhibition performance of polymer composite coatings in aggressive corrosive conditions was analyzed by salt spray test.
[0046] Polyaniline/ chitosan/ SiO2 composite were prepared by chemical oxidative polymerization of aniline in presence of o-phosphoric acid. First silica nanoparticles were added to the monomer aniline. The resultant mixture was added to the pre-cooled aqueous solution of chitosan in dilute o-phosphoric acid. Ammonium persulfate is used as oxidant for the reaction and added to reaction mixture in drop wise manner. Polymerization reaction mixture was continuously stirred for 4-5 hour. The synthesized polymer composite was filtered with the help of sintered G-2 funnel and washed with distill water till it get neutral pH. Washing of the composite was carried out to remove excess oxidant and oligomers from the polymer composite. The obtained residues were further dried.
[0047] Corrosion resistant coatings were applied on mild steel substrate by using electrostatic gun. Ball mill was used to blend the epoxy powder and polymer composite. These coatings were cured for one hour. The resultant coated mild steel substrates were used for electrochemical analysis and salt spray analysis.
[0048] Polyanisidine/ chitosan/ SiO2 composite were synthesized by a facile method of in situ oxidative polymerization. Chitosan aqueous solution was prepared by dissolving chitosan in o-phosphoric acid one (1) day before the reaction. Monomer anisidine was encapsulated on silica nanoparticles with continuous stirring. The obtained monomer slurry was added to the pre-cooled slurry of chitosan at -5 to 0oC and stirred for 2 hours. The aqueous solution of ammonium persulfate was added to the reaction mixture to initiate the polymerization. The reaction solution was continuously stirred for the 4-5 hours and yields greenish solution. The obtained composite solution was filtered and washed with distilled water. The filtered polymer composite was dried in vacuum oven.
[0049] The resultant dried composite was grind by using mortar & pestle, loaded in different Wt% in epoxy powder. Coating was fabricated by applying these powder compositions to mild steel substrates by using powder coating unit. These panels were cured for one (1) hour.
[0050] Polyaniline-co-o-anisidine/ chitosan/ SiO2 composite were synthesized by chemical oxidative copolymerization using ammonium persulfate as a oxidant in o-phosphoric acid medium. Equimolar concentration of monomers aniline and anisidine was encapsulated on silica nanoparticles with constant stirring. A pre-cooled solution of chitosan was prepared by dissolving 1wt% chitosan in aqueous solution of o-phosphoric acid. The monomer mixture was added to the chitosan slurry and poured in the triple wall reactor. The reaction mixture was continuously stirred and temperature was maintained at -5 to 0oC. The above solution was polymerized through in-situ copolymerization by using ammonium persulphate as an oxidant. The resultant precipitates was filtered out and washed thoroughly with distilled water. The obtained polymer composite was dried and grinded into fine powder using mortar and pestle.
[0051] Anticorrosive coating system is designed by blending the copolymer composite with epoxy powder. Various formulations were prepared by loading different wt% of copolymer composite. Mild steel panels have been used for the sample preparation. Surface of panels were cleaned with acetone and emery papers. Copolymer/epoxy coating was applied to mild substrates with help of powder coating unit. These coated mild steel samples were used for all electrochemical analysis (Tafel analysis). Mild steel substrates with dimension of 150 x 100 mm were subjected to salt spray analysis. Salt spray analysis is carried out to check anticorrosive performance of the coating. All the experimental conditions were maintained according to ASTM Standards (ASTMB117).
[0052] In typical synthesis monomers aniline and anisidine were adsorbed on the Flyash nanoparticles. This solution is added to pre-cooled slurry of chitosan in diluted o-phosphoric acid. This reaction mixture was stirred for one (1) hour at -5 to 0oC. Ammonium persulfate oxidant is dissolved in 0.2 ltr of distilled water and added to reaction mixture in drop wise manner. The reaction mixture is stirred for 4-5 hr and filtered using G-2 filtration funnel. The reaction product was washed thoroughly with distilled water and dried.
[0053] The obtained composite was ball milled with epoxy powder for the formulation of corrosion resistant coatings. Cleaned mild steel substrates were coated with these formulations and cured for one (1) hour. These coated panels were used for Tafel analysis as well as salt spray analysis. Bend test was carried out to check the adhesion of coating to the substrate and to examine for any visible crack in the coating.
Embodiments:
[0054] In one embodiment of the invention, the monomers selected for study are aniline and anisidine.
In another embodiment of the invention, bio-waste chitosan is dissolved in the reaction medium.
In another embodiment of the invention, the filler material like silica nano particles has been used for the polymerization.
In another embodiment of the invention, the reaction medium for polymerization is selected from phosphoric acid and the like.
[0055] In another embodiment of the invention, the oxidant such as ammonium persulphate or potassium persulphate, ferric chloride and the like has been used.
In another embodiment of the invention, the polymerization reaction condition was maintained at 0 to 5oC temperature.
[0056] In further embodiment of the invention, the loading of filler material in the polymeric matrix with respect to monomer was kept between 1 to 25 %.
In another embodiment of the invention, the content of oxidant to monomer was kept between 0.1 mole to 0.3 mole.
[0057] In another embodiment of the invention, the reaction medium for the analysis was phosphoric acid whose molar concentration with respect to monomer was kept between 0.1 to 0.5 mole.
[0058] In one embodiment of the invention, the reaction time of polymerization was kept between 2-6 hours.
[0059] In another embodiment of the invention, the powder obtained after filtration was dried in vacuum oven at 50-60oC.
[0060] In another embodiment of the invention, several blends from range of 1 to 6% were prepared by blending copolymer obtained after drying in epoxy powder.
In another embodiment of the invention, powder coating technique was used to coat the mild steel surfaces with epoxy mixed with copolymers blends.
[0061] In another embodiment of the invention, the curing of coated mild steel panels was carried out at 140-160oC.
[0062] In another embodiment of the invention, corrosion resistance behavior of the coated mild steel panels was examined by Tafel plots in saline water (3.5 % NaCl) and under aggressive conditions as per ASTM standards.

[0063] Now the generalized description is categorized with optimized parameters leading to standardization of protocol for the desired objectives to achieve. The following examples are given to illustrate the process of the present invention and should not be construed to limit the scope of the present invention:
Example 1
Synthesis of silica nanoparticles
[0064] The synthesis of silica nanoparticles was carried out by hydrolysis of tetra-ethylorthosilicates (TEOS) in ethanol and ammonia was used as catalyst. First ethanol (1.0 M) was mixed to (0.1M) aqueous ammonia solution. 20 ml of deionized water was added to this solution mixture and stirred for 2 hour. TEOS (0.05M) was added to this resulting solution and again stirred for 1 hour at room temperature. The appearance of white turbidity confirms the formation of SiO2 nanoparticles. This suspension was centrifuged at 10000 rpm to obtain silica nanoparticles and further this powder was calcined at 600?C for 6 hours. SEM and TEM studies of the samples were carried out to see the morphological characteristic which shows that size of the particles vary from 150 nm to 200 nm.

Example 2
Synthesis of polyaniline/ SiO2 in presence of o-phosphoric Acid
[0065] Silica nanoparticles in 15-30 wt. %, more specifically 20 wt. % with respect to aniline monomer have been added.
[0066] Synthesis of polyaniline/ SiO2 composite was carried out by taking 0.1 M of aniline which was adsorbed on silica nanoparticles at a temperature of 50-60oC. In the above reaction mixture, pre-cooled slurry of 0.2 M o-phosphoric acid is added. This reaction mixture was then stirred for one hour at -5 to 0oC in a triple walled reactor. In the above reaction mixture, 0.1M of ammonium persulfate is added very slowly drop by drop. Stirring was continued stirred for 4-5 hr and on completion of polymerization, the precipitate is filtered using sintered G-4 funnel. The reaction product was washed thoroughly with distilled water till the pH of the solution becomes neutral and then precipitate of the polymer composite was dried at 60-70 oC.
[0067] Anticorrosive coating was prepared by blending obtained polymer composite with snow white glossy epoxy powder No. HGC 1327 (bisphenol A + polyester) in different weight percent loading (1 to 6%). The mild steel substrates were cleaned before the coating using different size of grade of emery papers of grit size 120, 600, 800. The polymer/Epoxy mixture is powder coated on mild steel using a electrostatic gun. The synthesized copolymer composites were blended with the epoxy resin using a laboratory ball mill. Several compositions having different wt% proportions (1.0, 2.0, 3.0, 4.0 and 5.0) of copolymer composite with epoxy were prepared. The blended powder coating formulations were applied on the mild steel surface using an electrostatic spray gun held at 67.4 KV potential with respect to the substrate (grounded). The powder coated mild steel specimens were cured at 150 ?C in an oven for 1 hour. Coated mild steel samples of area 1x1 cm2 were used for electrochemical analysis (Tafel Parameters analysis) whereas for salt spray analysis, mild steel panels of dimensions 50 X 10 mm were used. Salt spray analysis was done according to the ASTM standard (ASTM B-117). All the coated samples of dimension 150 x 100 mm were placed in salt spray chamber at angle of 15 degree. An intentional cut mark was given on coated mild steel samples to check their resistance against ambient conditions. Salt spray test is performed at a constant temperature of 35 °C with 5.0% NaCl salt solution of (pH of 6.5-7.2). Salt solution was continuously sprayed in chamber and form mist in chamber. Temperature and humidity were also maintained throughout the test. All the coated steel panels were exposed to salt spray mist for 60 to120 days.

Example 3
Synthesis of polyanisidine/SiO2 in presence of o-phosphoric Acid
[0068] Silica nanoparticles in 15-30 wt. %, more specifically 20 wt. % with respect to anisidine monomer have been added.
[0069] Polyanisidine/ SiO2 composite were synthesized by polymerizing 0.1 M anisidine in aqueous acidic medium of o-phosphoric acid. Silica nanoparticles were adsorbed on monomer anisidine at 50-60 o C. 0.1M ammonium persulfate was added to the reaction mixture very slowly drop by drop. The reaction mixture was continuously stirred for 4-5 hour at -5 to 0oC. The resultant product was filtered and washed with distilled water till the pH 7 attained. The obtained product was dried at 60-70 o C under vacuum.
[0070] Prior to powder coating mild steel substrate surface was treated with different emery papers. The resultant polymer composite was blended with epoxy powder to formulate anticorrosive coating. Several composition having different Wt% (from 1% to 6%) loading of polymer composite in epoxy powder was prepared. Powder coating unit was used to coat blended compositions on mild steel substrate. Coated mild steel substrates were used to analyze the anticorrosive performance of the coating. All electrochemical analysis was carried out in 3.5% NaCl. Corrosion inhibition performance of polymer composite coatings in aggressive corrosive conditions was analyzed by salt spray test.
Example 4
Synthesis of polyaniline/Chitosan/SiO2 in presence of o-phosphoric Acid
[0071] Silica nanoparticles in 15-30 wt. %, more specifically 20 wt. % with respect to aniline monomer has been added with 1-5 wt% of chitosan, more specifically 1 wt. % chitosan.
Polyaniline/ Chitosan/ SiO2 composite were prepared by chemical oxidative polymerization of 0.1M aniline in presence of o-phosphoric acid. First silica nanoparticles were added to the monomer aniline at 50-60 o C. The resultant mixture was added to the pre-cooled aqueous solution of chitosan (1%) in dilute o-phosphoric acid. Polymerization reaction was carried out at -5 to 0oC. Ammonium persulfate 0.1M is used as oxidant for the reaction and added to reaction mixture in drop wise manner. Polymerization reaction mixture was continuously stirred for 4-5 hour. The synthesized polymer composite was filtered with the help of sintered G-2 funnel and washed with distill water till it get neutral pH. Washing of the composite was carried out to remove excess oxidant and oligomers from the polymer composite. The obtained residue is dried at 60-70 o C.
Corrosion resistant coatings were applied on mild steel substrate by using electrostatic gun. Ball mill was used to blend the epoxy powder and polymer composite. These coatings were cured at 150 o C for one hour. The resultant coated mild steel substrates were used for electrochemical analysis and salt spray analysis.
Example 5
Synthesis of polyanisidine/Chitosan/SiO2 in presence of o-phosphoric Acid
[0072] Silica nanoparticles in 15-30 wt. %, more specifically 20 wt. % with respect to anisidine monomer has been added with 1-5 wt% of chitosan, more specifically 1 wt. % chitosan.
[0073] Polyanisidine/ Chitosan/ SiO2 composite were synthesized by a facile method of in-situ oxidative polymerization. Chitosan (1%) aqueous solution was prepared by dissolving chitosan in o-phosphoric acid one day before the reaction. Monomer anisidine was encapsulated on silica nanoparticles with continuous stirring. The obtained monomer slurry was added to the pre-cooled slurry of chitosan at -5 to 0oC and stirred for 2 hours. The aqueous solution of ammonium persulfate 0.1M was added to the reaction mixture to initiate the polymerization. The reaction solution was continuously stirred for the 4-5 hours and yields greenish solution. The obtained composite solution was filtered and washed with distilled water. The filtered polymer composite was dried in vacuum oven at 60-70 o C.
[0074] The resultant dried composite was grind by using mortar & pestle, loaded in different Wt% in epoxy powder. Coating was fabricated by applying these powder compositions to mild steel substrates by using powder coating unit. These panels were cured at 150oC for one hour.
Example 6 (Best Combination with Best Mode)
Synthesis of polyaniline-co-o-anisidine/ Chitosan/ SiO2 in presence of o-phosphoric Acid
[0075] Silica nanoparticles in 15-30 wt. %, more specifically 20 wt. % with respect to aniline and anisidine monomer has been added with 1-5 wt% of chitosan, more specifically 1 wt. %.
[0076] Polyaniline-co-o-anisidine/ Chitosan/ SiO2 composite were synthesized by chemical oxidative copolymerization using ammonium persulfate as an oxidant in o-phosphoric acid medium. Equimolar concentration of monomers aniline 0.1M and anisidine 0.1 M was encapsulated on silica nanoparticles with constant stirring at 60 oC. A pre-cooled solution of chitosan was prepared by dissolving 1wt% chitosan in aqueous solution of 0.2M o-phosphoric acid. The monomer mixture was added to the chitosan slurry and poured in the triple wall reactor. The reaction mixture was continuously stirred and temperature was maintained at -5 to 0oC. The above solution was polymerized at -2oC through in-situ copolymerization by using ammonium persulphate (0.1M) as a oxidant. The resultant precipitates was filtered out and washed thoroughly with distilled water. The obtained polymer composite was dried at 60-70 o C and grinded into fine powder using mortar and pestle.
[0077] Anticorrosive coating system is designed by blending the copolymer composite with epoxy powder. Various formulations were prepared by loading different wt% of copolymer composite. Mild steel panels have been used for the sample preparation. Surface of panels were cleaned with acetone and emery papers. Copolymer/epoxy coating was applied to mild substrates with help of powder coating unit. These coated mild steel samples were used for all electrochemical analysis (Tafel analysis). Mild steel substrates with dimension of 150 x 100 mm were subjected to salt spray analysis. Salt spray analysis is carried out to check anticorrosive performance of the coating. All the experimental conditions were maintained according to ASTM Standards (ASTMB117).
Summary of Experiments and Observations
[0078] The present invention deals with one of the major problem faced by the researchers and engineers. Herein corrosion resistant coating based on the conducting polymers is developed for mild steel substrate exposed to the marine conditions. Among the various fillers materials silica nano-particles has been encapsulated in polymer matrix. Generally filler materials (silica nanoparticles) concentration in the matrix varies from 15 Wt% to 40 Wt%. Silica nanoparticles incorporated in the polymer matrix as it enhances the thermal and mechanical properties of the polymer matrix. Chitosan also has been incorporated in the matrix due to its film forming ability. A facile synthesis of polyaniline-co-o-anisidine/Chitosan/SiO2 has been carried out by chemical oxidative co-polymerization in aqueous medium of ortho-phosphoric acid. Both the monomers aniline 0.1M and anisidine 0.1M were absorbed on silica nanoparticles 20 Wt% with continuous stirring at 50 OC. Chitosan 1Wt% is dissolved in aqueous solution of 0.2M ortho-phosphoric acid. Monomers were added in the resulting solution and stirred for 2 hours. Ammonium persulfate 0.1M is added to the reaction solution. The reaction mixture is stirred for 4-5 hours at -2 OC as depicted in figure 1. The obtained product is filtered and washed with distilled water till pH 7 obtained. The resultant product is dried at 60 OC and grinded into mortar and pestle. Anticorrosive coating is prepared by blending the copolymer composite with epoxy powder in different wt% loading (1 to 5%). These blends were powder coated on mild steel substrate with the help of powder coating unit. The coated steel samples were baked at 150-160 OC. The following samples were used for electrochemical studies and salt spray analysis. The tafel plots figure (2,3 and 4) demonstrates that copolymer coatings exhibits low value of corrosion current density Icorr in comparison to bare steel sample. All the samples shows corrosion protection efficiency of >99% when exposed to highly saline conditions like 3.5% NaCl. Salt spray analysis is carried out to check the anticorrosive behaviour of coatings in aggressive corrosive conditions. Figure 5 & 6 shows the photographs of panels before and after the analysis. The copolymer composite coatings demonstrate excellent anticorrosive behaviour in aggressive conditions. In epoxy coating there is an extension of corrosion around the cut mark and slight delamination of coating is observed. While there is no extension of corrosion around the cut mark and delamination observed in conducting polymer coatings. Figure 7 shows the result of scratch test, there is no scratch observed for polymer coating. This demonstrates that copolymer coatings posse’s good adhesion to substrate. The bend test also shows similar results Figure 8, coatings were bend to 175o to check any type of degradation or crack in the coatings. There is no crack or any type of degradation is observed in copolymer coating, while a crack is observed in epoxy coating. Figure 9 shows the SEM micrographs and Edax pattern of copolymer composite. SEM micrographs show the uniform distribution of silica nanoparticles in polymer matrix and Edax confirms the presences the silica in the matrix. The SiO2 nanoparticles exhibit spherical morphology with the size ranging from 150-200 nm. The even distribution of filler materials in polymer matrix enhances the mechanical and thermal properties of the composite. The anticorrosive property of the coating is the combined effect of the silica nanoparticles, chitosan and conducting polymers.