Synthesis, characterization and corrosion protection properties of poly(N-(methacryloyloxymethyl) benzotriazole-co-glycidylmethacrylate) coatings on mild steel

The synthesis of copolymers from different feed ratios of N-(methacryloyloxymethyl) benzotriazole (MMBT) and glycidyl methacrylate (GMA) was achieved by using free radical solution polymerization technique and characterized using FT-IR and ¹³C NMR spectroscopy. The thermal stability of the synthesized copolymers was studied using thermogravimetric analysis (TGA). The corrosion performances of mild steel specimens dip coated with different composition of copolymers were investigated in 0.1 M HCl using potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) method. The polarization and impedance measurements showed different corrosion protection efficiency with change in composition of the copolymers. It was found that the corrosion protection properties are owing to the barrier effect of the polymer layer covered on the mild steel surfaces. However, it was observed that the copolymer obtained from 1:1 mole ratio of MMBT and GMA exhibited better protection efficiency than other combinations.     

Poly(N-ethylaniline) coatings on 304 stainless steel for corrosion protection in aqueous HCl and NaCl solutions

Poly(N-ethylaniline) (PNEA) coatings were grown by potentiodynamic synthesis technique on 304 stainless steel (SS) alloy from 0.1 M of N-ethylaniline (NEA) in 0.3 M oxalic acid solution. Characterization of adhesive and electroactive PNEA coatings was carried out by cyclic voltammetry, FT-IR spectroscopy and scanning electron microscopy (SEM) techniques. The protective properties of PNEA coatings on SS were elucidated using linear anodic potentiodynamic polarization, Tafel and electrochemical impedance spectroscopy (EIS) test techniques, in highly aggressive 0.5 M HCl and 0.5 M NaCl solutions. Linear anodic potentiodynamic polarization test results proved that PNEA coating improved the degree of protection against pitting corrosion in HCl and NaCl solutions. Tafel test results showed that PNEA coating appears to enhancement protection for SS in 0.5 M NaCl and 0.5 M HCl solutions. However, according to long-term EIS results, PNEA coating is better for the protection of SS electrodes during the long immersion period in NaCl compared to that in HCl medium.     

The electrochemical synthesis of poly(aniline-co-o-anisidine) on copper and their corrosion performances

The copolymer films PANI-co-POA and poly(aniline-co-o-anisidine) were carried out on copper (Cu) electrode, by applying two different scan rates (20 and 50 mV s⁻¹) and using two different thicknesses at high scan rate. Synthesizes were achieved under cyclic voltammetric conditions from 0.075 M aniline and 0.075 M o-anisidine containing sodium oxalate solutions. The synthesized copolymer films were strongly adherent and homogeneous in both cases. AC impedance spectroscopy (EIS), anodic polarization plots and open circuit potential–time curves were used to evaluate the corrosion performance of copolymer coated and uncoated electrodes in 3.5% NaCl. It was shown that the copolymer film coated at low scan rate exhibited a better property initially when compared with the copolymer film produced at high scan rate. However, it could not resist the attack of corrosion products, in longer time and meanwhile its barrier property significantly diminished. It was found that the thin copolymer film produced at high scan rate by its catalysing effect led to the formation of highly protective copper oxides on the surface whereby providing a better protection for long exposure times. It also emerged that the corrosion resistances of thin copolymer film produced at high scan rate and copolymer film synthesized at low scan rate were almost same and relatively higher for much longer periods when compared with the one observed for bare copper electrode.     

Electrochemical properties and corrosion protection of stainless steel for hot water tank

The state in which a stainless steel (STS) exhibits a very low corrosion rate is known as passivity, which is self-healing in a wide variety of environments. However, for those STS the corrosion includes pitting, crevice corrosion, galvanic corrosion, hydrogen embrittlement and stress corrosion cracking etc. And the corrosion resistance of STS is affected by area ratio, solution temperature and solution condition etc. Corrosion characteristics of STS 304, welding parts STS 316, STS 329 and STS 444 were investigated with parameters such as corrosion potential, galvanic current measurements, cathodic and anodic polarization behaviors as a function of area ratio and solution temperature in solution for hot water tank. It was found that galvanic current is affected by the area ratio, temperature and a kind of STS for hot water tank. Corrosion potential of welding part STS 316 was lower than that of STS 304, STS 329, STS 444 in solution for #1, #2 hot water tank. Therefore, it is suggested that the welding part STS 316 acts as anode for the other STSs. The amplitude of galvanic current between welding parts STS 316 and STS 304, STS 329, STS 444 in #1 solution is smaller than that in #2 solution. This is the reason that chloride ion quantity in #2 solution is more than that for #1 solution. And then welding part STS 316 corrodes easily by acting as anode compared to the other STS.     

Characterization and properties of poly(ethylene oxide) and its blends with poly (N-vinyl carbazole)

The calorimetric properties and dynamic mechanical behaviour of pure poly(ethylene oxide) (PEO) and its blends with poly(N-vinyl carbazole) (PNVK) have been examined as a function of composition in the range 50-100% PEO. Thermomechanical measurements indicate the presence of a phase separation in this blend. Using the Hoffman-Weeks plot no equilibrium melting point depression was found in any of the blends studied. Some kinetic interfacial effects were detected in the crystallization processes. For all blend compositions, the Avrami exponent is close to that obtained for pure PEO. The DMTA and DTA results suggest an incompatibility in this system.     

Corrosion resistant performance of hydrophobic poly(N-vinyl imidazole-co-ethyl methacrylate) coating on mild steel

Functional copolymers are often used as protective coating against corrosion. In this research article, we have applied poly(NVI-co-EMA) coating over the mild steel surface which provides barrier protection against corrosion in aggressive environment. Hydrophobic nature of the copolymer film may augment the corrosion resistance behavior and thermal stability of the copolymer also influences the corrosion protection. Thus, the coating precluded the corrosive elements and corrosion products from diffusing through the coating. EIS technique revealed that the mild steel coated with hydrophobic copolymer film, which is immersed in 3% NaCl solution provides excellent protection from corrosion. Further, it is evidenced by protection efficiency of the copolymer which is greater than 90%. The results from surface analysis techniques like SEM, AFM and FTIR also supports and confirms a very thin film on the metal surface with excellent anticorrosion effects.     

Electropolymerization of poly(N-ethyl aniline) on mild steel: Synthesis, characterization and corrosion protection

Poly(N-ethylaniline) (PNEA) coatings on the mild steel electrode were synthesized by electrochemical oxidation of N-ethylaniline using aqueous oxalic acid solutions as reaction medium. Electrodeposition was carried out by potentiodynamic, potentiostatic and galvanostatic synthesis techniques. Smooth, adhesive and thick PNEA coatings on mild steel could be electrosynthesized during sequential scanning of the potential region between −0.5 and 1.4 V versus SCE, with scan rate of 20 mV s⁻¹. The electrodeposited coatings were characterized by cyclic voltammetry, FT-IR and UV-vis techniques. Corrosion behavior of PNEA coated steels was investigated by linear anodic potentiodynamic polarization technique and Tafel test. Anodic potentiodynamic polarization results showed that electrodissolution current value of PNEA coated steel decreased about 90% compared to that of the uncoated steel in 0.5 M H₂SO₄ aqueous solution. Tafel plots showed also strong decrease of corrosion current for the PNEA coated electrode compared to the uncoated steel electrode in 3% NaCl as corrosive medium.     

Electropolymerized bilayer coatings of polyaniline and poly(N-methylaniline) on mild steel and their corrosion protection performance

Polyaniline (PANI) and poly(N-methylaniline) (PNMA) have been electrodeposited on mild steel from oxalic acid bath using cyclic voltammetric technique. Pretreatments like passivation and primer polymer coatings were required for effective coating. Differently stacked composite polymer layers on the metal surface by layer-by-layer approach have also been obtained and their properties have been compared with their corresponding copolymer coatings. FTIR study confirms the formation of electroactive polymer compounds on mild steel. Evaluation of these coatings in 3.5% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy reveals significant corrosion resistant behavior. Relatively higher corrosion protection is exhibited by copolymer coatings and composite-bilayer coatings than the corresponding homopolymer coatings. The composite metal–PANI–PNMA layer shows higher stability and better protection than the metal–PNMA–PANI layer.     

Electrochemical synthesis and corrosion protection properties of poly(o‐toluidine) coatings on low carbon steel

Uniform and strongly adherent poly(o‐toluidine) (POT) coatings have been synthesized on low carbon steel (LCS) substrates by electrochemical polymerization (ECP) of o‐toluidine under cyclic voltammetric conditions from an aqueous sodium tartrate solution. Cyclic voltammetry (CV), UV‐visible absorption spectroscopy, Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) measurements, and scanning electron microscopy (SEM) were used to characterize these coatings, which indicates that the sodium tartrate is a suitable medium for the ECP of o‐toluidine and it occurs without noticeable dissolution of LCS. Corrosion protection properties of the POT coatings were evaluated in aqueous 3% NaCl by the potentiodynamic polarization measurements and CV. The result of the potentiodynamic polarization demonstrates that the POT coating has ability to protect the LCS against corrosion. The corrosion potential was about 334 mV more positive in aqueous 3% NaCl for the POT‐coated LCS than that of bare LCS and reduces the corrosion rate of LCS almost by a factor of 50. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 685–695, 2005     

On the corrosion protection properties of fluoropolymer coatings

Fluoropolymers have attained great importance as coating materials because of their excellent resistance to high temperature, chemicals and organic solvents. Electrochemical impedance spectroscopy was used to study the corrosion protection properties both on undamaged fluoropolymer coatings and on samples with an artificial defect. The experimental results were interpreted on the basis of a proposed equivalent electrical circuit which best fits the experimental impedance spectra. In this way we observed the high quality of the fluorinated coatings compared with that of the corresponding hydrogenated polymer used as a reference. The protective properties of the fluoropolymer coatings studied can be related to chemical (fluorine and chlorine functional groups) and physical (good order of the polymeric chains) characteristics of the resins.     

Inhibition of steel corrosion by electrosynthesized poly(o-anisidine)-dodecylbenzenesulfonate coatings

Poly(o-anisidine)-dodecylbenzenesulfonate (POA-DBSA) coatings were synthesized on stainless steel from aqueous solution containing o-anisidine and dodecylbenzene sulfonic acid by using cyclic voltammetry. These coatings were characterized by Fourier transform infrared spectroscopy (FTIR), UV-vis absorption spectroscopy, scanning electron microscopy (SEM) and cyclic voltammetry (CV). Corrosion tests of these coatings were carried out in aqueous 3% NaCl solution by using open circuit potential (OCP) measurements, potentiodynamic polarization technique, cyclic potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS). The results reveal that POA-DBSA acts as a corrosion protective coating on steel and reduces the corrosion rate (CR) of steel almost by a factor of 14.5.     

Poly(o-ethylaniline) coatings for stainless steel protection

The poly(o-ethylaniline) coatings were electrochemically synthesized on 304-stainless steel by using cyclic voltammetry from an aqueous salicylate medium. Cyclic voltammetry, UV–vis absorption spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterize these coatings, which indicates that the aqueous salicylate solution is a suitable medium for the electrochemical polymerization of o-ethyaniline on 304-stainless steel. The performance of poly(o-ethylaniline) as protective coating against corrosion of 304-stainless steel in aqueous 3% NaCl was evaluated by the open circuit potential measurements, potentiodynamic polarization technique, cyclic potentiodynamic polarization measurements and electrochemical impedance spectroscopy. The results of the potentiodynamic polarization and cyclic potentiodynamic polarization demonstrate that the poly(o-ethylaniline) coating provides excellent protection to both localized and general corrosion of 304-stainless steel. The corrosion potential was about 0.190 V more positive in aqueous 3% NaCl for the poly(o-ethylaniline) coated steel than that of bare steel and reduces the corrosion rate of steel almost by a factor of 20.     

The influence of thin benzoate-doped polyaniline coatings on corrosion protection of mild steel in different environments

The corrosion process of mild steel in the presence of benzoate-doped polyaniline coatings exposed to different environments (3% NaCl, atmosphere, and the Sahara sand) has been investigated. This system was also tested for cathodic protection and it has proven more efficient comparing to mild steel alone. Possible mechanisms of the corrosion protection of mild steel in the presence of a polyaniline-based coating in different corrosion media were also proposed.     

Localized EIS characterization of corrosion of steel at coating defect under cathodic protection

Localized electrochemical impedance spectroscopy (LEIS) technique was used to investigate localized corrosion of steel at defect of coating and, furthermore, to determine the effects of cathodic protection (CP) on local electrochemical environment and the resultant corrosion reaction at the base of coating defect. The results demonstrated that corrosion of steel is dependent on CP potential and the defect geometry. For coated steel containing defect under appropriate CP potentials, cathodic reaction is dominated by reduction of oxygen. Mass-transfer of oxygen through solution layer and the defect with a narrow, deep geometry (the depth/width ratio is about 5.5) is the rate-limiting step for the corrosion process of steel. Even at a very negative potential, e.g., −1200 mV (SCE), the measured impedance spectroscopy is still associated with the diffusion-controlled charge-transfer reaction of steel at the base of defect. It is attributed to the fact that the applied CP is partially shielded by the defect with a narrow, deep geometry. With the negative increase of cathodic potential, charge-transfer resistance and the local impedance of electrode increase. It is attributed to the elevation of local alkalinity at the base of defect when the coated steel is under CP. This conclusion is subject to the condition that a significant cathodic disbonding of coating has not occurred. Furthermore, with the increase of test time, the charge-transfer resistance increases, which is attributed to the enhancement of the alkaline environment at the base of defect under CP with time.     

Corrosion inhibition by poly(N-ethylaniline) coatings of mild steel in aqueous acidic solutions

Poly(N-ethylaniline) (PNEA) coatings on mild steel have been electrodeposited from 0.1 to 0.5 M aqueous oxalic acid solutions containing 0.1 M N-ethylaniline (NEA) using potentiodynamic synthesis technique. The effect of oxalic acid concentration on the corrosion behavior of PNEA coated mild steel surfaces were investigated by DC polarization and electrochemical impedance spectroscopy (EIS) techniques in 0.1 M HCl and 0.05 M H₂SO₄ solutions. Corrosion test results showed that corrosion resistance of PNEA coatings decreases with increasing concentrations of oxalic acid in polymerization solution. Decreasing acidity of the polymerization solution causes more effective protection against corrosion in aqueous acidic corrosive medium.     

Electropolymerization, characterization and corrosion performance of poly(N-ethylaniline) on copper

Poly(N-ethylaniline) (PNEA) coatings were grown by cyclic voltammetry technique on copper from 0.1 M N-ethylaniline (NEA) in 0.3 M oxalic acid solution. The optimum conditions (e.g. upper potential limit, scan rate and cycle number) effect on corrosion performance of synthesized PNEA films were determined in order to obtain best protection results against corrosion. The electrodeposited coatings were characterized by cyclic voltammetry (CV), Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy and scanning electron microscopy (SEM). Redox parameters were found after electrochemical tests and results of stability tests of these films impart an electroactive behavior that is composed of both diffusion control and thin film behavior. In addition, corrosion performance of PNEA coatings were investigated in 0.1 M H₂SO₄ by Tafel extrapolation and electrochemical impedance spectroscopy (EIS) techniques.     

Electrochemical synthesis of bilayer coatings of poly(N-methylaniline) and polypyrrole on mild steel and their corrosion protection performances

Homopolymer and bilayer coatings of poly(N-methylaniline) (PNMA) and polypyrrole-dodecylsulfate (PPy-DS) have been electropolymerized on a mild steel (MS) surface by the potentiodynamic method in aqueous oxalic acid solutions. In order to include dodecylsulfate ion as dopant in the polypyrrole, sodium dodecylsulfate was also added to the polymerization solution of pyrrole. Characterization of coatings was carried out by the cyclic voltammetry, Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FESEM). Corrosion behavior of the polymer coated MS electrodes was investigated in highly aggressive 0.5 M HCl solution by the Tafel test and electrochemical impedance spectroscopy (EIS) techniques. Corrosion test revealed that among the protective coatings obtained, the PNMA/PPy-DS bilayer exhibited the best corrosion resistance at all immersion times.     

The corrosion protection of mild steel by single layered polypyrrole and multilayered polypyrrole/poly(5-amino-1-naphthol) coatings

Electrochemical synthesis of polypyrrole (PPy) and top coat of poly(5-amino-1-naphthol) (PANAP) on PPy films from oxalic acid solution was achieved on mild steel (MS) by cyclic voltammetry technique. The morphology and the structure of the films were investigated by scanning electron microscopy (SEM). The corrosion performance of this multilayer coating and single PPy coating were investigated in 3.5% NaCl solution by using open circuit potential (E_ocp)–time curves, polarization curves and electrochemical impedance spectroscopy (EIS). It was found that the multilayer PPy/PANAP coating could provide much better protection than single PPy coating for corrosion of MS. It was observed that corrosion performance of coatings was increasing with immersion period. This was explained by auto-undoping properties of PPy coatings during immersion in corrosive solution. The improved corrosion performance in the presence of PANAP top coat on PPy was explained by increase in barrier effect of bilayer films.     

Electrosynthesis of poly(aniline-co-o-phenylenediamine) film on steel and its corrosion protection performance

Poly(aniline-co-o-phenylenediamine) (Ani-co-oPD) has been electrosynthesized on steel surface by cyclic voltammetry technique from an aqueous oxalic acid electrolyte. The copolymer film was characterized by FTIR, UV, TGA, and SEM techniques. The corrosion protection performance of poly(Ani-co-oPD) film on steel was found out by impedance and Tafel polarization methods in 1% NaCl. The copolymer film was found to be highly corrosion resistant and a suitable mechanism for corrosion protection is suggested.     

Synthesis and characterization of poly(N-vinyl pyrrolidone-alt-maleic anhydride): Conjugation with bovine serum albumin

Alternate N-vinyl pyrrolidone/maleic anhydride (NVPMA) copolymers were obtained by radical solution polymerization in dioxane with various MA contents in the monomer feed. The conversion of each monomer was monitored by proton nuclear magnetic resonance spectroscopy (¹H NMR), and the kinetics investigation showed that both monomers had identical polymerization rates if both monomers were present in the reaction mixture. The presence of excess NVP in the polymerization medium increased the kinetics of the polymerization and the molar masses of the resulting polymers. This increase was attributed to a cosolvent effect due to NVP, which is a better solvent for the polymer than dioxane. The hydrolysis rate constant of the polymers increased with pH, and NVPMA copolymers were more prone to hydrolysis (by a factor 10) than the methyl vinyl ether ones. Finally, the immobilization of bovin serum albumin (BSA) was investigated. A 25 mM phosphate buffer (pH 5.5) was the best medium to covalently bind 5 BSA molecules onto a 29 kDa NVPMA copolymer and 13 BSA molecules onto a 58 kDa sample, with grafting efficiencies > 90%. Noncovalent interactions with the hydrolyzed form of the polymer and BSA occured at pHs lower than the isoelectric point of BSA, and the resulting complexes were insoluble in water. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3327–3337, 2001