Title of Invention

A PROCESS FOR THE PREPARATION OF CORROSION PROTECTION COPOLYMER COATING OF IRON BASED SURFACES

Abstract A process for the preparation of corrosion protection copolymer coating of iron based surfaces by mixing of aniline and o-phenetidine monomers in a ratio in the range of 1:1.5 to 1.5:1 in the presence of protonic acid with a pH in a range of 0 to 3, at ice temperature and stirring the said mixture, adding an oxidant slowly drop by drop to the said mixture at a temperature in a range of-5 to 5°C, stirring the reaction mixture for a period in a range of 4-6 hours, filtering the said reaction mixture after the completion of the polymerization, washing thoroughly the said mixture with water, neutralizing the washed copolymer with aqueous alkali and drying the copolymer at a temperature in a range of 50-60°C under vacuum. Coating of a copolymer layer on pretreated iron based surface, heating the coated iron based surface to a temperature in a range of 30-50°C for a time period in a range of 30 minutes to 60 minutes giving a hard copolymer coating.
Full Text The present invention relates to a process for the preparation of corrosion protection copolymer coating of iron based surfaces.
More particularly the invention relates to a copolymer of aniline and o-phenetidine and a process for the preparation of the said copolymer.
The corrosion of iron and mild steel is an enormous problem throughout the world. Giving an anticorrosion treatment to articles of iron and materials containing iron is considered essential for durability of the articles due to hostile environmental parameters of humidity, salinity of water. Many kinds of treatment, paints and coatings have been developed over the years to address this problem For a coating to protect iron against corrosion, it should restrict access of water, oxygen and other oxidants to the iron surface. In some instances, corrosion inhibitors such as zinc coatings or organic amines are used. Recently much interest has been shown in the use of conductive polymers in corrosion protection of articles made from iron or mild steel. These articles may be such as huge ships used for marine transport.
Reference may be made to disclosure by Thompson et. Al., in "Corrosion-Protective
Coatings from Electrically Conductive Polymers", Proceedings from Technology 2001, San
Jose, California. In this disclosure is reported conductive polymer coatings for the protection
of iron surfaces from corrosion. These coatings involved electrically conducting forms of
several polymers, including polyaniline which had been appropriately doped with additives
such as serving as electron acceptors to increase conductivity of the polymer. These
polymers were used by applying un doped chemically prepared polymers to the steel surface
and subsequent doping of the coated surface to the conductive

steel surface and subsequent doping of the coated surface to the conductive state. Doped polyaniline was converted to a non-conducting emeraldine base which was dissolved in an organic solvent such as, N-methyl-pyrrolidinone (NMP) and coated on steel after which the coating was doped to the conducting state. The dopants used were tosylate ions, zinc nitrate and tetracyanoethylene. After doping a top coat of standard fully cured epoxy was applied to provide abrasion resistance. In this disclosure the coating of the polymer dissolved in NMP is effected for curing by heating to a temperature of at least 95°C. The use of high temperature with NMP as the solvent is highly undesirable as during high temperature treatment the NMP releases toxic gases. This work reported a corrosion barrier coating for steel made from an electrically conducting polymer which resists the transfer of electrons from iron to the oxidizing environment. The coating was said to have two layers: an undercoat of polyaniline on steel surface and an epoxy top coat for durability. The bilayer coating was reported to be more effective in resisting corrosion than a coating with epoxy alone. In another disclosure (US Patent, 5441772 of August 1995) a method of protecting carbon steel substrates from corrosion environments is provided by a coating of emeraldine base which has been chemically prepared and cast onto the substrate from NMP solution. The coating also includes other polymers such as polyimides, epoxies and urethane linked diisocyanates, among others. This invention also suffers from the disadvantage of the use of NMP which uses high temperature treatment for effecting a protective coating.

US Patent #5441772 (August 1995) provides a method of protecting carbon steel substrates from corrosion environments by a coating of emeraldine base which has been chemically prepared and cast onto the substrate from NMP solution. The coating also includes other polymers such as polyimides, epoxies and urethane linked diisocyanates, among others. In this patent disclosure, emeraldine base is dissolved in N-methyl pyrrolidinone which is then applied on carbon steel substrates. A temperature of 80-90°C is required to evaporate the NMP solution resulting in toxic NMP vapours.
US Paten t# 5853621 (December 1998) describes an anti corrosion paint of the type comprising one or more polymeric binders dispersed in liquid medium with an effective amount of non-conductive conjugated polymers. In this patent disclosure, polyaniline is mixed with a dispersant from Daniel Products in a solvent propylene glycol methyl ether acetate and aromatic naptha 100. US Patent # 5922466 (July 1999) relates to the development of a composite comprising a metal substrate and a corrosion protecting layer on at least one major surface, a composition comprising a thermoset or thermoplastic polymeric matrix and a conductive filler component comprising polyaniline, and other conducting polymers. In this patent, a composition of thermoplastic or thermoset polymeric matrix along with polyaniline is applied on iron substrate. For thermoplastic coating a temperature ranging from 100-200°C is required which is the melting point of the polymeric material. This blend is then applied on the iron surface. In this case first the temperature needed is very high and secondly this type of process is not suitable for industrial applications because the coating can

be applied only when it is in the melt stage and once the temperature lowers down, solidification will start leading to the requirement of again raising the temperature to desired level to effect the coating..
US Patent # 6015613 (January 2000) provide a method of forming corrosion inhibition multilayer coatings. When the coating is bonded to a substrate, it forms an inter layer between the metal and substrate. The laminates serve to protect the metal surface from corrosion in acid, salt and alkaline corrosive environments. In the said patent disclosure, C1018 steel electrodes were brush coated with a dispersion of polyaniline and poly(butylmethylacrylate) in butyrolactone. The coating coupons were allowed to dry at 30°C in an air convection oven. An epoxy topcoat of Carboline 890 was then applied at 60°C. In this case, only a dispersion of polyaniline in solvent is used which may not spread uniformly on the surface and once the surface is exposed to hostile atmosphere, corrosion rate may be accelerated.
US Patent # 6239251 (May 2001) discloses a method of forming low molecular weight oligomers of aniline based compounds which are end fictionalized and capable of being reacted with other monomeric species to form a variety of copolymers. In this patent, aniline is polymerized in the presence of 1,4-phenylenediamine, 1,4-aminodiphenyl amine, n.n'diphenylhydrazine, benzidine and the like. The coating of the above copolymer was prepared by dissolving the copolymer in dimethylformamide (DMF) and then combining with epoxy resin in the form of bisphenol-A-diglycidyl ether. Curing was then done at 120°C for 1 pur. The temperature required for curing in the disclosure is 120°C.

The main objective of the present invention is to provide a conducting copolymer useful for corrosion protection coating of iron and mild steel which obviates the drawbacks as mentioned above.
Another objective of the present invention is to provide process for the preparation of copolymer of aniline and o-phenetidine as a common organic solvent soluble polymer useful for the prevention of corrosion of iron and mild steel in hostile saline atmosphere.
Yet another object of the present invention is to provide a single coat of copolymer for the anti corrosive coating.
An improved method of protection of corrosion for iron and mild steel is provided by applying to the surface of steel a coating of a copolymer of aniline and substituted aniline comprising of phenetidine, hexyl aniline and phenoxy aniline. As a further embodiment of our invention, mild steel is coated with a protective film of copolymer of aniline and substituted aniline which are soluble in common organic solvents unlike the parent polymer polyaniline base for which an organic solvent N-methyl pyrrolidinone (NMP) is used which requires 80-100°C for drying on the surface. In the present case a coating of copolymer mixed with other materials like polyimides, epoxy resins, CTE Resin is also applied on the surface for the corrosion protection of iron and mild steel against hostile environment like saline water comprising NaCI, MgCI2, BaCI2 and so on. The coating gives anti corrosive property which is stable for at least one year and upto a temperature of about 400 ° C

In the drawing accompanying this specification:
Figure 1 represents a graph showing various forms of copolymer of aniline and o-phenetidine. Fig 1(a) shows the complete reduced form of copolymer Fig 1(b) shows the base form of the copolymer Fully oxidized form of the copolymer is shown in Fig 1(c).
Accordingly the present invention provides a corrosion protection copolymer coating of iron based surface, which comprises; coating of a copolymer layer on pretreated iron based surfaces, heating the coated iron based surface to a temperature in a range of 30-50 ° C for a time period in a range of 30 minutes to 60 minutes giving a hard copolymer coating.
In an embodiment of the present invention the monomers aniline and o-phenetidine may be in a ratio of in a range of 1:1.5 -1.5:1. In another embodiment of the present invention the pretreatment of iron based surface may be done by conventional known means such as buffing, chemical cleaning.
In still another embodiment of the present invention the coating of pretreated iron based surface may be copolymer coating, mixture of coal tar epoxy and copolymer.
In yet another embodiment of the present invention the mixture of coal tar epoxy and copolymer may be in a range of 1-20%.
In a further embodiment of the present invention the copolymer corrosion protection coating may be stable upto a temperature of 400 ° C.

In stil further embodiment of the present invention the corrosion inhibition efficiency of the
coating may be at least 95-99%.
In another embodiment of the present invention the anticorrosive property of the coating is
for at least 1 year.
Accordingly, the present invention provides a process for the preparation of corrosion
protection copolymer coating of iron based surfaces which comprises mixing of aniline and
o-phenetidine monomers in a ratio in the range of 1:1.5 to 1.5:1 in the presence of protonic
acid with a pH in a range of 0 to 3, at ice temperature and stirring the said mixture, adding
an oxidant slowly drop by drop to the said mixture at a temperature in a range of -5 to 5°C,
stirring the reaction mixture for a period in a range of 4-6 hours, filtering the said reaction
mixture after the completion of the polymerization, washing thoroughly the said mixture
with water, neutralizing the washed copolymer with aqueous alkali and drying the
copolymer at a temperature in a range of 50-60°C under vacuum, coating of a copolymer
layer on pretreated iron based surface, heating the coated iron based surface to a temperature
in a range of 30-50°C for a time period in a range of 30 minutes to 60 minutes giving a hard
copolymer coating.
In an embodiment of the present invention the concentration of the monomers may be in a
range of 0.1 M to2.0 M.
In another embodiment of the present invention, the oxidant may be selected from
ammonium persulphate, potassium persulphate, sodium persulpahte, ferric chloride, ferric p-
toluene sulphonate.
In a further embodiment of the present invention, the concentration of oxidant may be in a
range between 0.1 M to 2.0 M.
In yet another embodiment of the present invention, the protonic acid may be selected a
group of p-toluene sulphonic acid, benzene sulphonic acid,

dodecylbenzene sulphonic acid, sulphosaliclic acid, sulphamic acid, hydrochloric
acid, sulphuric acid and the like.
In an embodiment of the present invention, the aqueous alkali may be selected
from a group of ammonium hydroxide, sodium hydroxide and potassium
hydroxide.
In another embodiment of the present invention, the strength of alkali hydroxide
may be in a range from 0.1 to 1.0 M
In still another embodiment of the present invention the good quality water may
be distilled water, de ionised water.
In a further embodiment of the present invention the copolymer may be stable up
to a temperature of 400 ° C.
The process of preparation of conducting polymer is described herewith.
Monomer aniline and monomer o-phenetidine are taken in a glass reaction
vessel containing concentrated hydrochloric acid kept at 0°C. This reaction
mixture is stirred and drop wise aqueous solution of an oxidant is added. The
oxidant may be ammonium peroxysulphate, potassium persulphate, sodium
persulphate, ferric chloride, ferric p-toluene sulphonate and the like..More
preferably ammonium peroxysulphate is taken. The reaction mixture is stirred
preferably for 4 hours, till a brownish precipitate of copolymer is obtained. The
mixture is filtered and washed thoroughly with good quality water and preferably
distilled water though de ionised water may also be suitably used,, till the colour
of the filtrate is colourless. The polymer so obtained is treated with aqueous
ammonia solution and stirred for about 2 hours. The reaction mixture is again

filtered and washed thoroughly with god quality water. The precipitate so
obtained is vacuum dried at about 55°C. The resultant copolymer was dissolved
in an organic solvent to get the solution. The organic solution used was
preferably methanol and the said copolymer solution was used on iron electrode
to study its behaviour as a corrosion preventive coat in saline water.
The Copolymer of aniline and phenetidine was coated on iron surface by
spraying/brush coating. Multiple coats were given on the surface and the amount
coated was determined by weighing the electrode before coating and after
coating.
Weight loss measurements and Tafel Plot Electrochemical measurements were
carried out to determine the corrosion inhibition efficiency.
In the weight loss experiments blank iron electrodes and iron electrodes coated
with copolymer were suspended in saline water preferably with 3.5% NaCI (This
value was taken because the saline water has this much % age of sodium
chloride in it) for 15 days. The weight of iron electrodes were then noted and the
weight loss in both cases were used for evaluating the corrosion inhibition
efficiency. By the following expression
Corrosion inhibition efficiency = [ (W1 - W2 ) / W1] x 100
where Wi is the weight loss of iron electrode in saline water without coat and W2
is the weight loss of iron electrode coated with copolymer in saline water.
Corrosion inhibition efficiency was also calculated by electrochemical technique
using Tafel Extrapolation Method where electrochemical parameters were
determined by taking iron electrode in 3.5 % NaCI and iron electrode coated with

copolymer in 3.5 % NaCI with Platinum as the counter electrode and saturated calomel electrode as the reference electrode. The parameters determined gave the corrosion inhibition efficiency of: 95.6 %
Besides giving a corrosion resistance to a bare iron based surface by a coat of copolymer, the corrosion inhibition efficiency may also be increased by applying coat of a mixture of an epoxy with the copolymer. Preferably a 10% mixture of coal tar epoxy mixed with copolymer may be used to coat the iron surface. However a mixture of 1-20% cola tar epoxy with copolymer may be used . In this case of coating of copolymer with a pre-coat of a mixture of coal tar epoxy and copolymer a corrosion inhibition efficiency of 99.995 was achieved.
Organic compounds and polymers inhibit corrosion by absorbing at the metal surfaces Modes of absorption are dependent on Chemical structure of the molecule like presence of ° bonds or available loan pair of electrons., type of metal surfaces, electrochemical potential at the metal solution surface and complexing of molecules with metal ions neutralizing corrodant.
In case of conducting polymer coating adsorption takes place via functionalised nitrogen atoms of polymer nucleus oriented towards the metal surface and through the de localized electrons with the aromatic rings parallel
to the electrode surface.
The novelty of the present invention is the low temperature processing (30-50 °C ) of application of co polymer coating on iron or mild steel substrates for anti corrosion with an efficiency of at least 95% A further novelty of the invention lies in eliminating the use of toxN methyl pyrrolidinone (NMP) Both?,

these novelties are realized due to the inventive step of preparation of copolymer of aniline and o-phenetidine by oxidation .
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.
Preparation of Copolymer
Example 1
0.1 mole of aniline and 0.1 mole of o-phenetidine are taken in a reaction vessel in which 1.0 N of hydrochloric acid is there and is kept at 1°C. The reaction mixture is stirred and drop wise aqueous solution of ammonium peroxydisulphate is added in one hours time., The reaction mixture is stirred for 4 hours, till a brownish precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with distilled water till the colour of the filtrate is colourless. The co polymer so obtained is treated with aqueous 0.1 M ammonia solution and stirred for 2 hours. The reaction mixture is again filtered and washed thoroughly with distilled water. The precipitate so obtained is vacuum dried at 55°C with constancy of temperature maintained to within ! 1° C. The copolymer solution in methanol was prepared which was used on iron electrode to study its behaviour as a corrosion preventive coat in saline water.
Example -2
0.1 mole of aniline and 0.1 mole of o-phenetidine are taken in a reaction vessel in which 1.0 M of p-toluene sulphonic acid is there and is kept at 0°C. The reaction mixture is stirred and drop wise aqueous solution of oxidant, ammonium peroxydisulphate, is added. The reaction mixture is stirred for 4

hours, till a dark brown precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with distilled water till the colour of the filtrate is colourless. The polymer so obtained is treated with aqueous 0.1 M ammonia solution and stirred for 2 hours. The reaction mixture is again filtered and washed thoroughly with distilled water. The precipitate so obtained is vacuum dried at 50°C. The copolymer solution in methanol was prepared which was used on iron electrode to study its behaviour as a corrosion preventive coat in saline water.
Example -3
0.1 mole of aniline and 0.1 mole of o-phenetidine are taken in a reaction vessel in which 1.0 M of p-toluene sulphonic acid is there and is kept at 0°C. The reaction mixture is stirred and drop wise aqueous solution of oxidant, potassium perusulphate, is added. The reaction mixture is stirred for 4 hours, till a dark brown precipitate of copolymer is obtained. The mixture is filtered and washed thoroughly with distilled water till the colour of the filtrate is colourless. The polymer so obtained is treated with aqueous 0.1 M ammonia solution and stirred for 2 hours. The reaction mixture is again filtered and washed thoroughly with distilled water. The precipitate so obtained is vacuum dried at 50°C. The copolymer solution in methanol was prepared which was used on iron electrode to study its behaviour as a corrosion preventive coat in saline water.

Preparation of Anti corrosion coating
Example-4
An iron electrode of dimension 4x2 cm2 was cleaned thoroughly by conventional buffing process and was then weighed. This cleaned bare iron electrode was kept in 3.5 % NaCI. Solution. Another iron electrode of similar dimensions was cleaned thoroughly by conventional buffing process and weighed. A solution of copolymer in methanol was prepared and a coating of the copolymer was applied on the surface of the second electrode. This second electrode was also kept in 3.5 % NaCI solution. The weight loss in both cases was measured after15 days. The weight loss in the second case was found to give corrosion inhibition efficiency of the order of 96.7 %.
Weight of the blank iron electrode = 16.37615 gms
Weight of blank iron electrode dipped in 3.5 % NaCI = 16.12827 gms
Weight loss = 0.25798 gms
Weight of the iron electrode coated with copolymer =16. 24615 gms Weight of the copolymer coated electrode dipped in 3.5 % NaCI =
16.23786 gms
Weight loss = 0.00829 gms
Corrosion inhibition efficiency = 96.7 %
Example 5
An iron electrode of dimension 4x2 cm2 was cleaned thoroughly by conventional buffing process and was then weighed. This cleaned bare iron electrode was kept in 3.5 % NaCI. Solution. Another iron electrode of similar dimensions was

cleaned thoroughly by conventional buffing process and weighed. To this cleaned iron electrode a coating of 10% coal tar epoxy mixed with copolymer was applied . This second epoxy coated iron electrode was also kept in 3.5 % NaCI solution. The weight loss in both cases was measured after15 days. The weight loss in the second case was found to give corrosion inhibition efficiency of the order of 99.99 %.
Weight of the blank iron electrode = 16.37615 gms
Weight of blank iron electrode dipped in 3.5 % NaCI = 16.12827 gms
Weight loss = 0.25798 gms
Weight of the iron electrode coated with epoxy+copolymer =
16.52586 gms Weight of the copolymer coated electrode dipped in 3.5 % NaCI =
16.5285 gms
Weight loss = 0.00001 gms
Corrosion inhibition efficiency = 99.99 %
Example 6
Corrosion inhibition efficiency was determined by electrochemical technique also using Tafel Extrapolation Method where electrochemical parameters were determined by taking iron electrode in 3.5 % NaCI and iron electrode coated with copolymer in 3.5 % NaCI with Platinum as the counter electrode and saturated calomel electrode as the reference electrode. The parameters determined gave the following results:

Fe in 3.5 % NaCI Fe coated with copolymer in 3.5 %
NaCI
Ecorr (mV) = -515, Ecorr (mV) = -492
I corr (mA/cm2) = 340 Icorr (mA/cm2) = 14.0
ba = 45 mV/dec, bc = 110 mV/dec ba = 52.2, bc = 115
I.E. % = - I.E. % = 95.6
The main advantages of the present invention are:
1. Copolymer is soluble in organic solvents like methanol, ethanol,
isopropanol, DMSO, DMF, NMP, THF
2. It is environmentally stable in the presence of air and moisture
3. The copolymer is thermally stable upto 400°C .
4. The copolymer coating may be applied on the surface for anticorrosion
effects at normal temperatures upto 40 °C


We claim :
1. A process for the preparation of corrosion protection copolymer coating of iron
based surfaces which comprises mixing of aniline and o-phenetidine monomers
in a ratio in the range of 1:1.5 to 1.5:1 in the presence of protonic acid with a pH
in a range of 0 to 3, at ice temperature and stirring the said mixture, adding an
oxidant slowly drop by drop to the said mixture at a temperature in a range of -5
to 5°C, stirring the reaction mixture for a period in a range of 4-6 hours, filtering
the said reaction mixture after the completion of the polymerization, washing
thoroughly the said mixture with water, neutralizing the washed copolymer with
aqueous alkali and drying the copolymer at a temperature in a range of 50-60°C
under vacuum, coating of a copolymer layer on pretreated iron based surface,
heating the coated iron based surface to a temperature in a range of 30-50°C for a
time period in a range of 30 minutes to 60 minutes giving a hard copolymer
coating.
2. A process as claimed in claim 1, wherein the concentration of the monomer is in
a range of 0.1 M to 2.0 M.
3. A process as claimed in claims 1-2 wherein the oxidant is selected from
ammonium persulphate, potassium persulphate, sodium persulphate, ferric
chloride, ferric p-toluene sulphonate.
4. A process as claimed in claims 1-3 wherein the concentration of oxidant is a
range between 0.1 M to 2.0 M.
5. A process as claimed in claims 1-4 wherein the protonic acid is selected from a
group of p-toluene sulphonic acid, benzene sulphonic acid, dodecylbenzene

sulphonic acid, sulphosaliclicacid, sulphamic acid, hydrochloric acid, sulphuric acid.
6. A process as claimed in claims 1-5 wherein the awueous alkali is selected from a
group of ammonium hydroxide, sodium hydroxide and potassium hydroxide.
7. A process as claimed in claims 1-6 wherein the water used is distilled water,
deionised water.
8. A process for the preparation of corrosion protection copolymer coating of iron
based surfaces substantially as herein described with reference to the examples
and drawing accompanying this specification.

Documents:

1276-del-2001-abstract.pdf

1276-del-2001-claims.pdf

1276-del-2001-correspondence-others.pdf

1276-del-2001-correspondence-po.pdf

1276-del-2001-description (complete).pdf

1276-del-2001-Description-(Provisional).pdf

1276-del-2001-Drawings-(24-12-2001).pdf

1276-del-2001-drawings.pdf

1276-del-2001-form-1.pdf

1276-del-2001-form-18.pdf

1276-del-2001-Form-2-(24-12-2001).pdf

1276-del-2001-form-2.pdf

1276-del-2001-form-3.pdf

1276-del-2001-form-4.pdf

1276-del-2001-form-5.pdf


Patent Number 253963
Indian Patent Application Number 1276/DEL/2001
PG Journal Number 37/2012
Publication Date 14-Sep-2012
Grant Date 07-Sep-2012
Date of Filing 24-Dec-2001
Name of Patentee COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH
Applicant Address RAFI MARG, NEW DELHI-110 001, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 SANDEEP KUMAR DHAWAN NATIONAL PHYSICAL LABORATORY, K S KRISHANAN MARG NEW DELHI-110012, INDIA
2 NIVEDITA SINGH NATIONAL PHYSICAL LABORATORY, K S KRISHANAN MARG NEW DELHI-110012, INDIA
PCT International Classification Number C09D 5/08
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA