[001] The present invention relates to synthesize and characterize conducting polymer composite as a corrosion inhibitor with superior corrosion resistance stability for mild steel in an an acidic environment.
BACKGROUND AND PRIOR ARTS OF THE INVENTION
[002] Mild steel is a material commonly used for the production and transportation of crude oil in the oil industry and natural gas due to its excellent mechanical properties. Several problems occur during transportation of crude oil in the pipelines, where the migrating ions come into contact with metal due to the breakdown of the oil-aqueous emulsion, which stimulates the corrosion process. Furthermore, the corrosion is enhanced by the presence of trace water and salts in the oil and the acidic media which are used in descaling and oil well acidification. In a strong acid medium, the corrosion processes produce structural damage to the steel. There are several types of corrosion inhibitors which are widely used to control the corrosion problem of low carbon steel upon exposure to acidic solutions, which vary from organic macromolecules to nanocomposites. These compounds are adsorbed onto the metallic surface, blocking the active corrosion sites. The applicability of these materials as corrosion inhibitors for metals in acidic media has been recognized for a long time. However, most of these materials are heavily toxic and environmentally hazardous; therefore, attempts have been carried out to search for eco-friendly treatment materials for metals in acid solutions. In the past few years, conducting polymers have been recognized as excellent corrosion inhibitors for metals in the acid environment. A small quantity of polymer may be effective in inhibiting the corrosion of metals in acidic medium. Polyaniline (PANI) has been a hot topic of intensive research due to its high environmental stability.
[003] Following are the works done so far in the field of conductive polymers based corrosion inhibitors

[004] US Patent 5532025 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 are mainly consist of inorganic fillers and organic resin. The organic resin mainly consists 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, cross-linkable styrenic regions, cross-linkable polyamide resins, rubber, elastomer, ionomers, mixture and there cross linkers.
[005] US patent- 6942899 relates to a 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 a 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 6150032 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 to 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.
[007] EP 0294013 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 degradative effects of cavitation.
OBJECTS OF THE INVENTION:
[008] The principal objective of the present invention is to design conducting polymer by in-situ oxidative polymerization.
[009] Another objective of the present invention is to design conducting polymer which when incorporated with suitable fillers can be used for prevention of corrosion in an acidic environment.
[0010] Yet another objective of the present invention is to describe the process of synthesis of conducting polymer by selecting specific monomer which shows corrosion inhibition response.
[0011] Still another objective of the present invention is to synthesize conjugated polymers with metal ions as dopants.

[0012] Further objective of the present invention is to show the utilization of metal-doped conducting polymer as excellent corrosion inhibitors for metals in the acidic environment.
SUMMARY OF THE INVENTION
[0013] Accordingly, the present invention provides a process for designing of metal-doped conducting polymer as excellent corrosion inhibitors in a reaction medium containing metal ions as dopant within the polymerization process. The method comprising:
(a) Synthesis of conducting polymer Polyaniline by a facile in situ oxidative
polymerization method in an aqueous medium.
(b) Loading of metal ions into the polymer matrix within the polymerization
process.
(c) Analysis of corrosion resistance performance of the metal-doped polymer
by weight loss test and potentiodynamic polarization (Tafel Plots).
[0014] Precisely, the present invention precisely discloses and claims a process for synthesizing conducting polymer of aniline comprising the steps of preparing an aqueous solution of 0.1 - 0.5 M aniline monomer; mixing said aqueous solution of aniline monomer with solution of a salt of a metal, preferably copper, more preferably copper sulfate in 0.1 - 0.5 M; adding dropwise aqueous solution of 0.1 M ammonium peroxydisulfate (APS) as an oxidant; isolating said synthesized metal doped conducting polymer from reaction mixture by filtration; and washing the resultant product with distilled water in order to remove oxidant and oligomers, followed by drying in the vacuum oven at 60°C. The polymerization is carried out at a temperature of 0-5 ±1.0°C for a period of 2-8 hours.

BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In the drawings accompanying this specification:-
Fig. 1: Schematic of the synthesis of copper doped Polyaniline composite by a chemical oxidative polymerization process, electrochemical workstation and Tafel plots of samples.
Fig. 2: FTIR spectra of (a) Cu-PANI-1 and (b) Cu-PANI-2
Fig. 3: XRD graph of Cu-PANI composite sample
Fig. 4: SEM image of Cu-PANI composite sample
Fig. 5: Tafel plots of Cu doped PANI in different concentration (a) without inhibitor, (b) 50 ppm, (c) 100 ppm, (d) 150 ppm and (e) 200 ppm
DETAILED DESCRIPTION OF THE INVENTION
[0016] 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 the 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 the invention and not intended to be taken restrictively.
[0017] Throughout the description and claims of this specification, the phrases "comprise" and "contain" and variations of them mean "including but not limited to", and are not intended to exclude other moieties, additives, components, integers or steps. Thus, the singular encompasses the plural unless the context otherwise requires. Wherever there is an indefinite article used, the specification is to be understood as contemplating plurality as well as singularity unless the context requires otherwise.

[0018] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification including any accompanying claims, abstract and drawings or any parts thereof, or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
[0019] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. Post-filing patents, original peer-reviewed research paper shall be published.
Materials and Reagents Used:
[0020] Copper(II) sulfate pentahydrate was purchased from Merck Chemicals, India. Aniline monomer and ammonium per sulfate (APS) were purchased from Rankem Limited, India. The monomer aniline was purified by distillation under reduced pressure, before use. The deionized water of a particular resistivity of 106 Q. cm was utilized to get ready dilute or aqueous solutions. All other chemicals were of analytical reagent grade and utilized as received.
[0021] The present invention describes a process for designing of metal-doped conducting polymer as excellent corrosion inhibitors in a reaction medium

containing metal ions as dopant within the polymerization process. The method briefly comprising synthesizing of conducting polymer Polyaniline by a facile in situ oxidative polymerization method in an aqueous medium; loading of metal ions into polymer matrix within the polymerization process; and analysis of 5 corrosion resistance performance of the metal-doped polymer by weight loss test and potentiodynamic polarization (Tafel Plots).
Embodiments
[0022] In one embodiment of the invention, the monomer selected for study is 10 aniline.
[0023] In another embodiment of the invention, Copper Sulphate is dissolved in the reaction medium.
[0024] In another embodiment of the invention, the ammonium per sulfate (APS) has been used for the polymerization.
15 [0025] In another embodiment of the invention, the reaction medium for polymerization selected is aqueous and the like.
[0026] In another embodiment of the invention, the oxidant such as ammonium persulphate or potassium persulphate, ferric chloride and the like have been used.
[0027] In another embodiment of the invention, the polymerization reaction 20 condition was maintained at 0 to 5oC temperature.
[0028] In further embodiment of the invention, the ratio loading of Cu metal ion in the polymeric matrix with respect to monomer was kept 1 to 1.
[0029] In another embodiment of the invention, the content of oxidant to monomer was kept between 0.1 moles to 0.1 moles.
25 [0030] In one embodiment of the invention, the reaction time of polymerization
was kept between 2-6 hours.
8

[0031] In another embodiment of the invention, the powder obtained after filtration was dried in a vacuum oven at 50-60oC.
[0032] In another embodiment of the invention, the inhibiting performance of metal-doped polymer was evaluated by weight loss test and potentiodynamic 5 polarization (Tafel Plots).
[0033] The overall process for synthesizing conducting polymer of aniline selected for the corrosion inhibitor was selected polyaniline, wherein one of the monomer at least has a bulky group at ortho position of cyclic ring, in the presence of metal ions in suitable medium chosen from aqueous, hydrochloric
10 acid, sulphuric acid and the likes, further comprises designing of conducting polymers (polyaniline) by emulsion polymerization of aniline monomer in presence of oxidants such as, either standalone or in combination, ammonium persulfate (APS), dodecyl benzene sulphonate (DBS), ferric chloride (FeCl3), ferric phosphate (FePO4) or the likes, which when incorporated with suitable
15 metal ions, electrochemical analysis of the metal-doped conducting polymer as corrosion inhibitors, and further weight loss study for Mild Steel in presence of inhibitors in 1.0 M H2SO4. The samples were further analyzed by Tafel Plot methods and by weight loss study for Mild Steel in presence of inhibitors in 1.0 M H2SO4, HCl and the likes. The samples of the process showed 93% inhibition
20 efficiency.
[0034] Conducting polymer polyaniline may be synthesized by chemical oxidative polymerization using metal ions as a dopant. For the preparation of metal ions, doped polyaniline different molar ratio of monomer 0.1 – 0.5 M was taken in aqueous solution. The aniline monomer solution was then mixed with a 25 metal salt solution. The polymerization was initiated by the dropwise addition of an oxidant. The polymerization was carried out at a temperature of 0-10 ±1.0oC for a period of 2-8 h. The synthesized metal doped conducting polymer was isolated from the reaction mixture by filtration and washed with distilled water to
9

remove oxidant and oligomers, followed by drying in the vacuum oven. The prepared samples were designated as Cu-PANI-1 and Cu-PANI-2, respectively.
[0035] 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. However, the best mode requirement is served through the examples.
Example 1
Synthesis of copper metal ions doped Polyaniline
[0036] Conducting polymer polyaniline have been synthesized by chemical oxidative polymerization using copper metal ions as a dopant. For the preparation of metal ions, doped polyaniline different molar ratio of a monomer such as (0.1 M aniline) and (0.2 M aniline) was taken in aqueous solution. The aniline monomer solution was then mixed with copper sulfate solution. The polymerization was initiated by the dropwise addition of aqueous solution of 0.1 M ammonium peroxydisulfate (APS) which acts as an oxidant. The polymerization was carried out at a temperature of 0-5 ±1.0°C for a period of 2-8 h. The synthesized metal doped conducting polymer was isolated from the reaction mixture by filtration and washed with distilled water to remove oxidant and oligomers, followed by drying in the vacuum oven at 60°C. The prepared samples were designated as Cu-PANI-1 and Cu-PANI-2, respectively.
[0037] The potentiodynamic polarization method used for calculating Tafel parameters that were examined by electrochemical workstation Metrohm Autolab PGSTAT100 and three electrodes electrochemical setup.

Table 1: Tafel parameters for Mild Steel in 1.0 M H2SO4 containing a different concentration of inhibitors

Inhibitor's name Inhibitor's l^corr lcorr I.E (%)
concentration (Volts) (uA/cm2)
Without inhibitor — -0.559 927 ~
Cu-PANI-1 50 -0.509 435 51
100 -0.479 262 70
150 -0.463 210 74
200 -0.441 162 81
50 -0.482 254 71
Cu-PANI-2 100 -0.463 192 78
150 -0.441 147 82
200 -0.427 55 93
Table 2: Weight loss study for Mild Steel in presence of inhibitors in 1.0 M 5 H2SO4

Inhibitor's name Inhibitor cone, (ppm) Initial Weight of iron(mg)
before immersion Final weight
after
immersion
(mg) Weight loss
(%)
Without inhibitor - 32450.5 19620.2 41.00
Cu-PANI-1 50 32870.2 20670.6 38.21

100 32897.6 25905.6 21.81

150 34677.2 29536.6 15.69

200 32555.0 28640.5 13.10
Cu-PANI-2 50 33453.0 25545.5 24.62

100 32565.6 28338.3 13.75

150 32941.0 29932.5 10.25

200 33205.5 32207.3 2.85

We Claim:

A process for synthesizing conducting polymer of aniline comprising the steps of:
a) preparing an aqueous solution of 0.1 - 0.5 M aniline monomer;
b) mixing said aqueous solution of aniline monomer with solution of a salt of a metal, preferably salt of copper, more preferably copper sulfate in 0.1-0.5 M;
c) adding dropwise an aqueous solution of 0.1 M ammonium peroxydisulfate (APS) as an oxidant;
d) isolating said synthesized metal doped conducting polymer from reaction mixture by filtration; and
e) washing the resultant product with distilled water in order to remove oxidant and oligomers, followed by drying in the vacuum oven at 60°C.
The process as claimed in claim 1, wherein 0.1 and 0.2 M aniline monomer is taken for the required preparation of an aqueous solution.
The process as claimed in claim 1, wherein the polymerization is carried out at a temperature of 0-5 ±1.0°C for a period of 2-8 h.