Field of the Invention

The present invention relates to Advanced Inorganic - Organic Geopolymeric Corrosion Protective Coating Material for Mild Steel.
The process enables in obtaining advanced inorganic - organic geopolymeric coating material for mild steel utilizing fly ash, sodium hydroxide, sodium
silicate, silica fume , iron oxide red, water, epoxy resin and amine hardner by a process which involves together mechano-chemical grinding of raw materials
viz. fly ash, sodium hydroxide, sodium silicate, iron oxide red resulting in solid state chemical reaction among them to produce inorganic geopolymeric
precursor material in solid powder form. Coating material is obtained by adding silica fume, water, epoxy resin and amine hardner to tailored precursor
material.
Conventional coating materials used for protection of corrosion of mild steel are based on organic polymeric materials which suffers from drawback of
VOC emissions, utilization of toxic chemicals in their formation and also they immediately catches fire. Therefore coating materials which obivates these
drawbacks and possess good adhesion to substrate and corrosion protection properties are still in demand.
The present invention essentially provides
1.Advanced inorganic - organic geopolymeric coating material for mild steel utilizing fly ash, sodium hydroxide, sodium silicate, iron oxide red, silica fume , water, epoxy resin and amine hardner as raw materials.
2.The process involves together mechano-chemical grinding of raw materials viz. fly ash, sodium hydroxide, sodium silicate, iron oxide red in appropriate combinations, resulting in solid state chemical reaction among them to produce inorganic gepolymeric precursor material in solid powder form containing nano sized compounds of quartz, mullite, .hematite, sodium silicate, sodium aluminium silicate, sodium aluminium

oxide, iron silicate, aluminium iron oxide, formed by solid state chemical reaction among raw materials.
3. Coating material is obtained by adding silica fume, water, epoxy resin and amine hardner to inorganic gepolymeric precursor material and containing nano sized compounds of quartz, mullite, hematite, sodium aluminium silicate hydrate, sodium silicate, sodium aluminium silicate, iron oxide hydroxide, sodium iron oxide silicate hydrate, epoxy resin and amine hardner.
4. Developed coating material contain hybrid inorganic organic uniform dense geopolymer matrix which provide improved corrosion protection, adhesion strength.
Background of the Invention
Reference may be made to article " Effect of Geopolymer Coating on Mild Steel , authored by Farah Farhana, Muhammad Faiz Fazill, H. Kamarudin et al Solid State Phenomena 273:175-180 ■ April 2018, wherein synthesis of geopolymer was reported using class F fly ash , sodium hydroxide solution (NaOH) and sodium silicate solution . The alkaline activators were mixed with fly ash to produce the geopolymer paste which acts as a coating material. The mixture was placed in molds and reinforcement bar were embedded in geopolymer paste. Corrosion behavior of reinforcement bars were observed by using Open Circuit Potential (OCP) testing indicated that samples are in passivity region. Adhesion strength test and morphologicl analysis was laso performed . For adhesion strength, day 14 got the highest results compared day 7 and day 3 which the results are 2.0 Mpa, 1.9 Mpa and 1.5 Mpa respectively The drawbacks of the study coating material is that, it is based on only inorganic matrix which exhibit poor adhesion and corrosion protection properties.

Reference may also be made to the article "A Study on Corrosion Behavior of Reinforcement Bar Embedded in Geopolymer Paste by Open Circuit Potential authored by Z.F. Farhana, H. Kamarudin, Azmi Rahmat and A.M. Mustafa Al Bakri, Australian Journal of Basic and Applied Sciences, 7(5): 230-235, 2013 , wherein studies on corrosion behavior of reinforcement bar has been reported in several geopolymer environments by using the open circuit potential (OCP) method. The OCP of reinforcement bar was recorded with time. From the Pourbaix diagram, all the potential values were located in passivity region. The oxide formed the passive layer to protect the reinforcement bar from corrosion The drawbacks of the study is again presence of inorganic matrix only leading to poor adhesion, porosity and corrosion protection properties.
Reference may also be made to the article Sodium Silicate Free Geopolymer As Coating Material: Adhesion To Steel , authored by Irfan Khan, Azizli Khairun Azizi et al, 1st international electronic conference on materials, 26st May to 10th June 2014 wherein, class F-fly ash based sodium silicate free geopolymers were synthesized and used for coating application at 60°C.A maximum of 3.8 MPa adhesion strength was produced by geopolymer and it was found that geopolymers gained maximum strength within first 3 days. Infra Red spectroscopy , X-rays diffractometery (XRD) and scanning electron microscopy were used for characterization and results indicated that final product revealed the formation of geopolymer without addition of sodium silicate. It can be concluded that sodium silicate free geopolymer has the potential to be used as a sustainable and green coating material for metals protection. The drawbacks of the study is presence of inorganic matrix only and also absence of sodium silicate resulting in poor adhesion to the substrate.

Reference may also be made to the article Polyaniline grafted polyurethane coatings for corrosion protection of mild steel surfaces authored by Himadri S. Karmakar, Ravi Arukula, J. Appl. Polym. Sci. 2018, 135, 45806 wherein polyaniline (PANI), poly-/r?-aminophenol (PmAP) and poly-o-anisidine (PoA) networks were prepared by blending conducting polyanilines with isocyanate-containing prepolyurethanes for coating on mild steel plates . Free-standing polyurethane films were obtained after a moisture cure for several days to ensure complete reaction of the excess isocyanate coated on mild steel panels. The results indicated superior corrosion-resistant properties of coated plates. The drawbacks of the coating material is utilization of organic polymers only which suffers from drawback of VOC emissions. . Reference may also be made to the article Corrosion protection of mild steel by coatings containing polyaniline authored by Wei-KangLu, Ronald L.EIsenbaumer and Bernhard Wessling, Synthetic Metals, Volume 71, Issues 1-3, 1 April 1995, Pages 2163-2166 , wherein The anti-corrosion performance of polyaniline coated mild steel samples exposed to artificial brine and dilute hydrochloric acid environments was evaluated. The drawbacks of the coating material is utilization of organic polymers only which suffers from drawback of VOC emissions.
Reference may also be made to patent application Midly alkaline thin inorganic corrosion protective coating for metal substrates, application number WO2009 143144 A1, inventors Thomas S. Smith, Jasdeep Sohi et al, wherein neutral to alkaline inorganic chrome-free conversion coating composition is reported that can be applied directly to a metal without phosphatizing pre-treatment for providing corrosion protection. The conversion coating composition is based on metals like zirconium, titanium, and hafnium, vanadium, niobium, and tantalum and also organic resins like epoxy resin, a polyvinyl dichloride resin, an acrylic-based resin, a

methacrylate-based resin, a styrene-based resin, a polyurethane, and a mixture thereof. The drawbacks of the developed coating material composition is that , it is based on costly metal based raw materials and organic resins which suffers from drawback of VOC emissions. Reference may be made to the article Corrosion protection of mild steel in different aqueous media via epoxy/nanomaterial coating: preparation, characterization and mathematical views, authored by Ziad T.Khodair, Anees A., Khadom, Hassan A.Jasim, Journal of Materials Research and Technology, Volume 8, Issue 1, January-March 2019, Pages 424-435 wherein corrosion rates of mild steel in different aqueous solutions under different operating conditions were reported by weight loss technique in the absence and presence of epoxy coating. In presence of coating, corrosion rates reduced in acidic solutions and poor performance of the coating was observed in saline solution. Effect of addition of magnesium oxide (MgO) nanoparticles was also studied. Maximum coating efficiency was 97% in acidic solution, while the lower one was 29.8% in saline solution in absence of nanoparticles. Nano scale MgO improve the coating performance with maximum value of 93.7% with epoxy coating in saline solutions. Several mathematical models were suggested to correlate the operating condition with corrosion rate. The drawbacks of the developed composition prepared for coating material is presence of nanoparticles which make them costly. Further addition of nanoparticles in epoxy resin was carried out by simple dispersion only without chemical bonding . All these drawbacks prohibit them from economic viability.
Reference may be made to patent application Inorganic phosphate corrosion resistant coatings, patent application number EP2510134A1, inventors Arun S. Wagh, Vadym Drozd, wherein phosphate coatings composition consisting of acidic phosphate and alkaline metal oxide/hydroxide components that inhibit corrosion of steel and other metals are reported. The drawback of the

composition is presence of inorganic matrix only resulting in poor flexibility, aesthetics, porosity brittle nature which prohibit them from economic vibility.
From the above mentioned prior art various issues to be addressed and problems to be solved are as follows:
a)Most of the coating materials used for protection of corrosion of mild steel are based on utilization of organic polymeric resins which although provides good adhesion to substrate and aestetics but suffers from drawback of VOC emissions and utilization of toxic chemicals in their formation.
b) The coating materials based on inorganic materials suffers from drawback of poor adhesion and high porosity, low flexibility and impact resistance. Their aesthetics is also not good.
c) Bonding between coating and mild steel is physical only thus poor in nature
d) In conventional geopolymer based coating materials,
i. the process is environment unfriendly as involves addition of hazardous alkaline solution.
ii. Contain inorganic matrix only. Lack of organic molecules in the matrix resulting in non uniform distribution of reacting species and development of non homogeneous matrix with large nanosize of silico aluminous species and also their broad range of distribution.which prohibits them from techno-economic viability.
To overcome these drawbacks the present process involves:
a) Developement of geopolymer based coating materials contain inorganic and organic species

b) Utilization of fly ash as raw material which is coal combustion residue and waste of thermal power plant.
c) coating material involves use of of epoxy resin and amine hardner as an additive only which does not suffer from drawback of VOC emissions.
d) There is chemical bond between coating and mild steel which is strong
e) Utilization of silica fume provides dense matrix with low porosity.
f) Iron oxide red provides colour as well as helps in formation of protective barrier layer between mild steel and environment
g) The process of development of coating material is environment friendly as it does not involves handling of hazardous alkaline solution.
To over come these drawbacks ,the present invention enables in preparation of inorganic organic geopolymer based corrosion protective coating material for mild steel substrate by solid state chemistry of together mechano chemical grinding of raw materials, resulting in formation of inorganic geopolymeric precursor material in solid powder form Coating material is obtained by addition of silica fume, water, epoxy resin and hardener to geopolymeric precursor material. Thus enables in further broadening the application spectrum of the conventional geopolymer based coating materials.
Objects of the Invention
The main object of the present invention is to provide a process for the development of inorganic organic geopolymer based corrosion protective coating material for mild steel substrate useful for further broadening the application spectrum of the conventional geopolymer based coating materials which obviates the drawbacks of the hitherto known prior art as detailed above.

Another object of the present invention is to provide inorganic organic
geopolymer based corrosion protective coating material for mild steel
substrate based on fly ash, sodium hydroxide, sodium silicate, silica fume ,
iron oxide red, water, epoxy resin and amine hardener.
Still another object of the present invention is to provide inorganic
geopolymeric precursor material in solid powder form by together mechano-
chemical grinding of raw materials viz. fly ash, sodium hydroxide, sodium
silicate, iron oxide red in appropriate combinations in a ball mill for period of
8 hours.
Still another object of the present invention is to provide inorganic
geopolymeric precursor material containing nano sized comopounds of
quartz, mullite, .hematite, sodium silicate, sodium aluminium silicate, sodium
aluminium oxide, iron silicate, aluminium iron oxide phases formed by solid
state chemical reaction among raw materials.
Still another object of the present invention is to provide coating material by
adding water, silica fume epoxy resin and amine hardner to geopolymeric
precursor material by continuous stirriring with mechanical stirrer
Still another object of present invention is to provide inorganic organic
geopolymeric coating material containing nano sized compounds of quartz,
mullite, hematite, sodium aluminium silicate hydrate, sodium silicate, sodium
aluminium silicate, iron oxide hydroxide, sodium iron oxide silicate
hydrate,epoxy resin and amine hardner.
Yet another object of the present invention is to provide coating material
contain hybrid inorganic organic uniform dense geopolymer matrix which
provide improved corrosion protection and adhesion strength
Accordingly the present invention provides process for preparation of
"Advanced Inorganic - Organic Geopolymeric Corrosion Protective Coating
Material for Mild Steel " which comprises together mechano- chemical dry
grinding of raw materials fly ash in the range of 75 to 90 % by weight ,

solid sodium hydroxide in the range of 10 to 15 % by weight , sodium
silicate in the range of 5 to 15 % by weight, iron oxide red in range of 2.5
to 10 % by weight using a ball mill for a period ranging from 8 to 12 hours, to
produce inorganic geopolymeric precursor material in solid form in nano size
which was reacted with silica fume (in range of 0.5 to 5 % by weight), water
(in range of 30 to 60 % by volume ) then epoxy resin (in range of 2.5 to 10
% by weight) and amine hardener ( in range of 0.5 to 2.5 % by weight ) by
continuous stirriring with mechanical stirrer resulting in formation of inorganic
organic coating material which was coated on mild steel by spray coating
technique and the coated plates were dried at room temperature for 18-24
hours and cured in hot air oven at 40-60°C for a period of 8-12 hours
duration and were removed and then tested for a) adhesion strength b)
scratch resistnce c) corrosion protection and d) thickness using standard
procedures.
In an embodiment of the present invention, the raw materials used for
preparation of geopolymeric coating material are fly ash , solid sodium
hydroxide ,sodium silicate , and additionally includes iron oxide red.
In another embodiment of the present invention, the raw materials used for
preparation of geopolymeric coating material are fly ash , solid sodium
hydroxide ,sodium silicate and additionally includes silica fume.
In another embodiment of the present invention, the raw materials used for
preparation of geopolymeric coating material are fly ash, solid sodium
hydroxide ,sodium silicate , and additionally includes water.
In another embodiment of the present invention, the raw materials used for
preparation of geopolymeric coating material are fly ash , solid sodium
hydroxide ,sodium silicate , and additionally includes epoxy resin.
In another embodiment of the present invention, the raw materials used for
preparation of geopolymeric coating material are fly ash, solid sodium
hydroxide ,sodium silicate and additionally includes amine hardner.

In another embodiment of the present invention, together mechano chemical
dry grinding of raw materials fly ash, solid sodium hydroxide ,sodium silicate,
iron oxide red is carried out using ball mill for a period of 8 hours resulting in
solid state, simultaneous mechano - chemical reaction among them to form
inorganic geopolymeric precursor material .
In another embodiment of the present invention, geopolymeric coating
materials is prepared by adding silica fume, water , epoxy resin and amine
hardner to inorganic geopolymeric precursor material by continuous
mechanical stirriring.
In still another embodiment of the present invention, developed coating
material was coated on mild steel plates by spray coating technique.
In still another embodiment of the present invention, coated plates were dried
at room temperature for 18-24 hours and cured in hot air oven at 40-60°C
for a period of 8-12 hours duration .
In still another embodiment of the present invention, coated plates were
removed and then tested for a) adhesion strength and b) scratch resistance
and c) corrosion protection and d) thickness using standard procedures.
Summary of an Invention
The novelty of the present invention with respect to prior art lies in the fact that it enables in preparation of inorganic organic geopolymer based corrosion protective coating material for mild steel substrate by solid state chemistry of together mechano chemical grinding of raw materials, fly ash, solid sodium hydroxide, sodium silicate, iron oxide red in a ball mill for a period of 8 hours resulting in formation of inorganic geopolymeric precursor material in solid powder form containing nano sized compounds of quartz, mullite, .hematite, sodium silicate, sodium aluminium silicate, sodium aluminium oxide, iron silicate, aluminium iron oxide formed by solid state mechano chemical reaction among raw materials. Coating material is

obtained by addition of silica fume, water, epoxy resin and amine hardener to geopolymeric precursor material and containing nano sized compounds of quartz, mullite, hematite, sodium aluminium silicate hydrate, sodium silicate, sodium aluminium silicate, iron oxide hydroxide, sodium iron oxide silicate hydrate,epoxy resin and amine hardner. It enables in further broadening the application spectrum of the conventional geopolymer based coating materials.
The process enables in obtaining advanced inorganic - organic geopolymeric coating material for mild steel utilizing fly ash, sodium hydroxide, sodium silicate, iron oxide red, silica fume , water, epoxy resin and hardner by a process which involves together mechano-chemical grinding of raw materials viz. fly ash, sodium hydroxide, sodium silicate, iron oxide red in in a ball mill for a period of 8 hours resulting in solid state chemical reaction among them to produce inorganic geopolymeric precursor material in solid powder form containing nano sized comopounds of quartz, mullite, .hematite, sodium silicate, sodium aluminium silicate, sodium aluminium oxide, iron silicate, aluminium iron oxide phases.Coating material is obtained by adding silica fume, water, epoxy resin and .amine hardner to geopolymeric precursor material. Developed inorganic organic coating material containing nano sized compounds of quartz, mullite, hematite, sodium aluminium silicate hydrate, sodium silicate, sodium aluminium silicate, iron oxide hydroxide, sodium iron oxide silicate hydrate,epoxy resin and amine hardner.
The following examples are given by way of illustration of the working of the invention in actual practice and therefore should not be construed to limit the scope of the present invention.
EXAMPLE 1 For making coating material, 1650 gms of fly ash, 100 gms of solid sodium hydroxide, 100 gms sodium silicate, 41.25 gms iron oxide red were together mechano chemically dry grinded in a ball mill for a period of 8 hours. The

100 gms of dry grinded material was reacted with silica fume 2 gms dissolved in 40 ml water, epoxy resin 10 gms, and amine hardner 2.5 gms by continuous mechanical stirriring for development of coating material. The obtained coating material was coated on mild steel plates of size 100 mm x 100 mm x 1mm by spray coating technique. The coated plates were dried at room temperature for 18 hours and cured in hot air oven at 45 °C for a period of 8 hours duration. There after the coated plates were removed from the hot air oven. The samples so obtained were tested for their adhesion strength using De Felsko Positest automatic pull off adhesion strength tester. The samples were found to posses adhesion strength of 13.5 MPa.Corrosion measurements were performed using salt spray chamber of Advanced equipments indicated that no rust was observed upto 92 hours duration.
EXAMPLE 2
For making coating material, 1550 gms of fly ash, 195 gms of solid sodium hydroxide, 205 gms sodium silicate, 48.75 gms iron oxide red were together mechano chemically dry grinded in a ball mill for a period of 8 hours. The 100 gms of dry grinded material was reacted with silica fume 1 gms dissolved in 40 ml water, epoxy resin 4.99 gms and amine hardner 1.25 gms by continuous mechanical stirriring for development of coating material. The obtained coating material was coated on mild steel plates of size 100 mm x 100 mm x 1mm by spray coating technique. The coated plates were dried at room temperature for 18 hours and cured in hot air oven at 45 °C for a period of 8 hours duration. Thereafter the coated plates were removed from the hot air oven. The coated samples so obtained were tested for adhesion strength (ASTM D 4541), scratch resistance (IS 101) and thickness (ASTM B244).. Accelerated corrosion test was performed in salt spray chamber (ASTM B117). Results indicated that adhesion strength of coated mild steel plates was found to be 15.20 MPa. Scratch resistance

test indicated that coating can withstand upto 4.200 kg load and upto this load needle cannot penetrate the coating and touch the mild steel surface. Thickness of coating was found to be 177 urn. Interpretation of results of salt spray test after 168 hours of exposure indicated that on the basis of evaluation of painted or coated specimens subjected to corrosive environments (ASTM D-1654), rating number for coating which is rating of failure at scribe is 4. It is representative mean creepage of rust from scribed area. Scale and description of rust ratings for evaluating degree of rusting on painted steel surfaces (ASTM D-610) indicated that the rating is 5-G. Rust distribution type is general and rust grade is 5 based on percentage of surface area rusted which is greater than 1 % and upto 3 %. Reduction in Adhesion strength after 168 hours of exposure in salt spray chamber was found to be 0.9 %.
EXAMPLE 3 For making coating material, 1500 gms of fly ash, 250 gms of solid sodium hydroxide, 200 gms sodium silicate, 97.5 gms iron oxide red were together mechano chemically dry grinded in a ball mill for a period of 8 hours. The 100 gms of dry grinded material was reacted with silica fume 2 gms dissolved in 40 ml water, epoxy resin 5 gms and amine hardner 1.24 gms by continuous mechanical stirriring for development of coating material. The obtained coating material was coated on mild steel plates of size 100 mm x 100 mm x 1mm by spray coating technique. The coated plates were dried at room temperature for 18 hours and cured in hot air oven at 45 °C for a period of 8 hours duration. Thereafter the coated plates were removed from the hot air oven. The coated samples so obtained were tested for adhesion strength (ASTM D 4541), scratch resistance (IS 101) and thickness (ASTM B244). Accelerated corrosion test was performed in salt spray chamber (ASTM B117). Results indicated that adhesion strength of coated mild steel plates was found to be 15.86 MPa. Scratch resistance test indicated

that coating can withstand upto 4.300 kg load and upto this load needle cannot penetrate the coating and touch the mild steel surface. Thickness of coating was found to be 168 urn. Interpretation of results of salt spray test after 168 hours of exposure indicated that on the basis of evaluation of painted or coated specimens subjected to corrosive environments (ASTM D-1654), rating number for coating which is rating of failure at scribe is 5. It is representative mean creepage of rust from scribed area. Scale and description of rust ratings for evaluating degree of rusting on painted steel surfaces (ASTM D-610) indicated that the rating is 4 -G. Rust distribution type is general and rust grade is 4 based on percentage of surface area rusted which is greater than 3.0 % and upto 10 % . Reduction in Adhesion strength after 168 hours of exposure in salt spray chamber was found to be 2.83 %.
EXAMPLE 4 For making coating material, 1600 gms of fly ash, 210 gms of solid sodium hydroxide, 140 gms sodium silicate, 97.5 gms iron oxide red were together mechano chemically dry grinded in a ball mill for a period of 8 hours. The 100 gms of dry grinded material was reacted with silica fume 1.5 gms dissolved in 40 ml water, epoxy resin 5 gms and amine hardner 1.25 gms by continuous mechanical stirriring for development of coating material. The obtained coating material was coated on mild steel plates of size 100 mm x 100 mm x 1mm by spray coating technique. The coated plates were dried at room temperature for 18 hours and cured in hot air oven at 45 °C for a period of 8 hours duration. Thereafter the coated plates were removed from the hot air oven. The coated samples so obtained were tested for adhesion strength (ASTM D 4541), scratch resistance (IS 101) and thickness (ASTM B244). Accelerated corrosion test was performed in salt spray chamber (ASTM B117). Results indicated that adhesion strength of coated mild steel plates was found to be 15.03 MPa. Scratch resisstance test indicated

that coating can withstand upto 4.000 kg load and upto this load needle cannot penetrate the coating and touch the mild steel surface.. Thickness of coating was found to be 169 urn. Interpretation of results of salt spray test after 168 hours of exposure indicated that on the basis of evaluation of painted or coated specimens subjected to corrosive environments (ASTM D-1654), rating number for coating which is rating of failure at scribe is 5. It is representative mean creepage of rust from scribed area. Scale and description of rust ratings for evaluating degree of rusting on painted steel surfaces (ASTM D-610) indicated that the rating is 5 -G. Rust distribution type is general and rust grade is 5 based on percentage of surface area rusted which is greater than 1.0 % and upto 3.0 % . Reduction in Adhesion strength after 168 hours of exposure in salt spray chamber was found to be 1.0%.
EXAMPLE 5 For making coating material, 1650 gms of fly ash, 200 gms of solid sodium hydroxide, 100 gms sodium silicate, 146.25 gms iron oxide red were together mechano chemically dry grinded in a ball mill for a period of 8 hours. The 100 gms of dry grinded material was reacted with silica fume 2.0 gms dissolved in 40 ml water, epoxy resin 10 gms and amine hardner 2.5 gms by continuous mechanical stirriring for development of coating material. The obtained coating material was coated on mild steel plates of size 100 mm x 100 mm x 1mm by spray coating technique. The coated plates were dried at room temperature for 18 hours and cured in hot air oven at 45 °C for a period of 8 hours duration. Thereafter the coated plates were removed from the hot air oven. The coated samples so obtained were tested for adhesion strength (ASTM D 4541), scratch resistance (IS 101) and thickness (ASTM B244). Accelerated corrosion test was performed in salt spray chamber (ASTM B117). Results indicated that adhesion strength of coated mild steel plates was found to be 16.48 MPa. Scratch resistance

test indicated that coating can withstand > 5.000 kg load and upto this load needle cannot penetrate the coating and touch the mild steel surface. Thickness of coating was found to be 182 um. Interpretation of results of salt spray test after 168 hours of exposure indicated that on the basis of evaluation of painted or coated specimens subjected to corrosive environments (ASTM D-1654), rating number for coating which is rating of failure at scribe is 8. It is representative mean creepage of rust from scribed area. Scale and description of rust ratings for evaluating degree of rusting on painted steel surfaces (ASTM D-610) indicated that the rating is 6 -G. Rust distribution type is general and rust grade is 6 based on percentage of surface area rusted which is greater than 0.3 % and upto 1.0 % . Reduction in Adhesion strength after 168 hours of exposure in salt spray chamber was found to be 2.3 %.
EXAMPLE 6 For making coating material, 1470 gms of fly ash, 253 gms of solid sodium hydroxide, 227 gms sodium silicate, 97.5 gms iron oxide red were together mechano chemically dry grinded in a ball mill for a period of 8 hours. The 100 gms of dry grinded material was reacted with silica fume 3.0 gms dissolved in 40 ml water, epoxy resin 10 gms and amine hardner 2.5 gms by continuous mechanical stirriring for development of coating material. The obtained coating material was coated on mild steel plates of size 100 mm x 100 mm x 1mm by spray coating technique. The coated plates were dried at room temperature for 18 hours and cured in hot air oven at 45 °C for a period of 8 hours duration. Thereafter the coated plates were removed from the hot air oven. The coated samples so obtained were tested for adhesion strength (ASTM D 4541), scratch resistance (IS 101) and thickness (ASTM B244).. Accelerated corrosion test was performed in salt spray chamber (ASTM B117). Results indicated that adhesion strength of coated mild steel plates was found to be 16.10 MPa. Scratch resistance test indicated

that coating can withstand > 5.000 kg load and upto this load needle cannot penetrate the coating and touch the mild steel surface. Thickness of coating was found to be 185 urn. Interpretation of results of salt spray test after 168 hours of exposure indicated that on the basis of evaluation of painted or coated specimens subjected to corrosive environments (ASTM D-1654), rating number for coating which is rating of failure at scribe is 6. It is representative mean creepage of rust from scribed area. Scale and description of rust ratings for evaluating degree of rusting on painted steel surfaces (ASTM D-610) indicated that the rating is 6-G. Rust distribution type is general and rust grade is 6 based on percentage of surface area rusted which is greater than 0.3 % and upto 1.0 %. Reduction in Adhesion strength after 168 hours of exposure in salt spray chamber was found to be 0.8 %.
EXAMPLE 7 For making coating material, 1600 gms of fly ash, 230 gms of solid sodium hydroxide, 120 gms sodium silicate, 195 gms iron oxide red were together mechano chemically dry grinded in a ball mill for a period of 8 hours. The 100 gms of dry grinded material was reacted with silica fume 5.0 gms dissolved in 40 ml water, epoxy resin 10 gms and amine hardner 2.5 gms by continuous mechanical stirriring for development of coating material. The obtained coating material was coated on mild steel plates of size 100 mm x 100 mm x 1mm by spray coating technique. The coated plates were dried at room temperature for 18 hours and cured in hot air oven at 45 °C for a period of 8 hours duration. Thereafter the coated plates were removed from the hot air oven. The coated samples so obtained were tested for adhesion strength (ASTM D 4541), scratch resistance (IS 101) and thickness (ASTM B244). Accelerated corrosion test was performed in salt spray chamber (ASTM B117). Results indicated that adhesion strength of coated mild steel plates was found to be 16.36 MPa. Scratch resisstance test indicated

that coating can withstand > 5.000 kg load and upto this load needle cannot penetrate the coating and touch the mild steel surface. Thickness of coating was found to be 190 um. Interpretation of results of salt spray test after 168 hours of exposure indicated that on the basis of evaluation of painted or coated specimens subjected to corrosive environments (ASTM D-1654), rating number for coating which is rating of failure at scribe is 8. It is representative mean creepage of rust from scribed area. Scale and description of rust ratings for evaluating degree of rusting on painted steel surfaces (ASTM D-610) indicated that the rating is 5 -G. Rust distribution type is general and rust grade is 5 based on percentage of surface area rusted which is greater than 1.0 % and upto 3.0 %. Reduction in Adhesion strength after 168 hours of exposure in salt spray chamber was found to be 1.5 %.
To further assess the corrosion resistance performance of the developed material, anodic polarization curve was recorded. All the experiments were performed in three electrode electrochemical system using a potentistat model number CH 1604 CH Instruments Inc., USA.The coated mild steel plates (area: 40mm x 35mm x1mm, of different compositions discussed in examples) were used as the working electrode, with Ag/AgCI and platinum foil as the reference and counter electrodes respectively. The electrolyte was 3.5 wt% NaCI solution. The potentials have been reported vs the Ag/AgCI reference electrode. Anodic polarization curve was recorded at an applied potential in the range of -1.2 V to 0.6 V at scan rate of 0.1 V/sec. These results confirmed that in the measured potential range at any constant potential, the coated plates showed significantly lower current density compared to the uncoated plates further confirming the good anticorrosion property in the developed coating material.
The main advantages of the present invention are:

The developed advanced inorganic - organic geopolymeric corrosion protective coating material for mild steel substrate is advantageous due to following reasons:
a) Developed geopolymer based coating materials contain inorganic and organic species.
b) Utilization of fly ash as raw material which is coal combustion residue and waste of thermal power plant.
c) The coating materials possess good adhesion to substrate and no porosity unlike inorganic coating materials which suffers from drawback of poor adhesion and high porosity.

d) Coating material involves use of of epoxy resin and amine hardner as an additive only which does not suffer from drawback of VOC emissions unlike common organic coating materials which are based on utilization of organic polymeric resins which suffers from drawback of VOC emissions and utilization of toxic chemicals in their formation.
e) There is chemical bond between coating and mild steel which is strong whereas conventional coating materials are based on physical bonding which is poor in nature

f) Utilization of silica fume provides dense matrix with low porosity.
g) Iron oxide red provides colour as well as helps in formation of protective barrier layer between mild steel and environment
h) The process of development of coating material is environment friendly as it does not involves handling of hazardous alkaline solution unlike conventional geopolymer based coating materials, based on environment unfriendly process of addition of hazardous alkaline solution.

We claim:

1. Advanced inorganic-organic geopolymeric corrosion protective coating material for mild steel comprises
a) fly ash (75 to 90 weight %);
b) solid sodium hydroxide (10 to 15 weight %);
c) sodium silicate ( 5 to 15 weight %);
d) iron oxide red ( 2.5 to 10 weight %);
which were together mechanochemically grinded in ball mill to form material characterised as the inorganic geopolymeric precursor material. The inorganic geopolymeric precursor obtained was reacted with silica fume (0.5 to 5 weight %), water (30 to 60 volume %), epoxy resin (2.5 to 10 weight %) and amine hardener (0.5 to 2.5 weight %) by continuous stirriring with mechanical stirrer to obtain coating material.
2. Advanced inorganic-organic geopolymeric corrosion protective coating material for mild steel as claimed in Claim 1 wherein inorganic geopolymeric precursor so obtained in solid form containing nano sized comopounds of quartz, mullite, hematite, sodium silicate, sodium aluminium silicate, sodium aluminium oxide, iron silicate, aluminium iron oxide phases.
3. Advanced inorganic-organic geopolymeric corrosion protective coating material for mild steel as claimed in Claim 1 wherein coating material so obtained by reacting inorganic geopolymeric precursor with silica fume , water , epoxy resin and amine hardener containing nano sized comopounds of quartz, mullite, hematite, sodium aluminium silicate hydrate, sodium silicate, sodium aluminium silicate, iron oxide hydroxide, sodium iron oxide silicate hydrate, epoxy resin and amine hardner.
4. Advanced inorganic-organic geopolymeric corrosion protective coating material for mild steel as claimed in Claim 1 wherein the coating material

so obtained was coated on mild steel plates of size 100 mm x 100 mm x 1 mm by spray coating technique.
Advanced inorganic-organic geopolymenc corrosion protective coating material as claimed in claim 1 was coated on mild steel by spray coating technique and the coated plates were dried at room temperature for 18-24 hours and cured in hot air oven at 40-60°C for a period of 8-12 hours duration.
A process for advanced inorganic-organic geopolymenc corrosion protective coating material for mild steel comprises together mechano-chemical dry grinding of fly ash (75 to 90 weight %), solid sodium hydroxide (10 to 15 weight %), sodium silicate (5 to 15 weight %) iron oxide red ( 2.5 to 10 weight %) using a ball mill for a period ranging from 8 to 12 hours to produce inorganic geopolymeric precursor material in solid form in nano size which was reacted with silica fume (0.5 to 5 weight %), water (30 to 60 volume %), epoxy resin (2.5 to 10 weight %) and amine hardener (0.5 to 2.5 weight %) by continuous stirriring with mechanical stirrer resulting in formation of inorganic organic coating material.