Corrosion Protection Of Mild Steel Research Articles

Protection of mild steel corrosion with new thia-derivative Salens in 0.5 M H2SO4 solution

The corrosion inhibition of mild steel in 0.5 M sulfuric acid by two newly synthesized Schiff bases namely, 4-X-2-{[2-(2-pyridin-2-yl-ethylsulfanyl) ethylimino] methyl}-phenol [X = –NO2 (S1) and –OMe (S2)] has been investigated in the temperature range 298–318 K using Tafel polarization and electrochemical impedance spectroscopy (EIS) methods. The inhibition efficiency of both S1 and S2 increases with increase in inhibitor concentration. The variation in inhibition efficiency depends on the type of functional group substituted in the benzene ring. It was found that the presence of the methoxy group in the Schiff base (S2) better facilitates the adsorption of molecules on the surface than is the case with S1. Tafel polarization showed that both Schiff bases are mixed corrosion inhibitors. The Temkin isotherm was found to provide an accurate description of the adsorption behavior of the Schiff bases. Calculation of thermodynamic parameters such as ΔGads0, ΔHads0 and ΔSads0 shows that the inhibitive action of the inhibitors is in the following order S1 < S2.

Water-Based Polyaniline/Montmorillonite/Epoxy Composite Coatings for the Corrosion Protection of Mild Steel

Polystyrene sulfonic acid (PSSA) doped water-dispersible polyaniline (PANI) /montmorillonite (MMT) clay composites were firstly synthesized by intercalation polymerisation in aqueous medium and characterized by XRD and FT-IR. The results showed exfoliated silicate nanolayers of MMT clay dispersed in the PANI matrix and has interaction involving hydrogen bonding between the PSSA-PANI chain and the surface of the MMT clay layer. This composites is more thermal stable than that of without clay samples and results in good stable temperature-dependent dc conductivity [σdc(T)] as temperature changed. The composite anticorrosion coatings of PANI/MMT and waterborne epoxy resin emulsion (EP) were prepared by mixture in aqueous medium and used for corrosion protection of mild steel. Open circuit potential (OCP), Electrochemical impedance spectroscopy (EIS) and Tafel plot demonstrated that the PANI/MMT/EP composite coatings have better anticorrosion properties than PANI/EP, MMT/EP and PANI/MMT/EP mixture. It’s impedance and corrosion potential is higher and the corrosion current density is lower. The anticorrosion coatings are environmental friendly because of water dispersion medium. Introduction

A comparative study of the corrosion inhibition of mild steel in sulphuric acid by 4,4-dimethyloxazolidine-2-thione

The corrosion protection of mild steel in a 2.5 M H 2SO 4 solution by 4,4-dimethyloxazolidine-2-thione (DMT) was studied at different temperatures by measuring changes in open circuit potential (OCP), potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). Corrosion current densities calculated from EIS data were comparable to those obtained from polarisation measurements. Results showed that DMT inhibited mild steel corrosion in a 2.5 M H 2SO 4 solution and indicated that the inhibition efficiencies increased with the concentration of inhibitor, but decreased proportionally with temperature. Polarisation curves showed that DMT is a mixed-type inhibitor. Changes in impedance parameters suggested the adsorption of DMT on the mild steel surface, leading to the formation of protective films. The DMT adsorption on the mild steel surface followed the Langmuir adsorption isotherm. The kinetic and thermodynamic parameters for dissolution and adsorption were investigated. Comprehensive adsorption (physisorption and chemisorption) of the inhibitor molecules on the mild steel surface was suggested based on the thermodynamic adsorption parameters.

Corrosion protection of mild steel by applying TiO2 nanoparticle coating via sol-gel method

TiO2 nanoparticle coatings possess good thermal and electrical properties and they are resistant to oxidation, corrosion, erosion and wear in high temperature environments. This property is very important factor in the applications such as pipelines, castings and automotive industry. In this investigation a uniform TiO2 nanoparticle coating has been applied on mild steel, using sol-gel method. The coating was deposited on mild steel substrate by dip coating technique. The morphology and structure of the coating were analyzed using SEM, AFM and X-ray diffraction. The anticorrosion performances of the coating have been evaluated by using electrochemical techniques. It is worthy to note that the film uniformity was retained in high temperatures and no crack and flaking off from the substrate was observed. The Tafel polarization measurements provide an explanation to the increased resistance of TiO2 nanoparticle coated mild steel against corrosion and icorr was decreased from 18.621 to 0.174 μA/cm2.

Investigation of some oleochemicals as green inhibitors on mild steel corrosion in sulfuric acid

The inhibitive effect of four oleo chemicals (namely; 2-Pentadecyl-1,3-imidazoline (PDI), 2-Undecyl- 1,3-imidazoline (UDI), 2-Heptadecyl-1,3-imidazoline (HDI), 2-Nonyl-1,3-imidazoline (NI)), regarded as green inhibi- tors, were studied for the corrosion protection of mild steel in 0.5 M H2SO4. The methods employed were weight loss, potentiodynamic polarization and electrochemical imped- ance techniques. Scanning electron microscopy (SEM) was carried out on the inhibited and uninhibited metal samples to characterize the surface. The purity of synthesized inhibitors was checked by FT-IR and NMR studies. The inhibition efficiency increased with increase in inhibitor concentration, immersion time and decreased with increase in solution temperature. No significant change in IE values was observed with increase in acid concentration. The best performance was obtained for UDI possessing 96.2% inhibition efficiency at 500 ppm concentration. The adsorp- tion of the compounds on the mild steel surface in the presence of sulfuric acid obeyed Langmuir's adsorption isotherm. The values obtained for free energy of adsorption and heats of adsorption suggest physical adsorption. The addition of inhibitor decreased the entropy of activation suggesting that the inhibitors are more orderly arranged along the mild steel surface. The potentiodynamic polari- zation data indicate mixed control. The electrochemical impedance study further confirms the formation of a protective layer on the mild steel surface through the inhibitor adsorption.

Synthesis and corrosion protection aspects of poly(o-toluidine)/CdO nanoparticle composite coatings on mild steel

This study examines the possibility of using poly(o-toluidine)/CdO (POT-CdO) nanoparticle composite coating for corrosion protection of mild steel in chloride environment. The POT-CdO nanoparticle composite coating was synthesized on mild steel from aqueous tartrate solution containing CdO-nanoparticles (size ~18 nm) by using cyclic voltammetry. These coatings were characterized by cyclic voltammetry, UV–Visible absorption spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction measurements. The corrosion protection aspects of the resulting POT-CdO nanocomposite structure were investigated in aqueous 3% NaCl solution by potentiodynamic polarization technique and electrochemical impedance spectroscopy. The results of these investigations reveal that the POT-CdO nanoparticle composite acts as a protective coating on mild steel and reduces the corrosion rate of mild steel almost by factor of 70.

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.

Comparison of the corrosion protection of mild steel by polypyrrole–phosphate and polypyrrole–tungstenate coatings

AbstractThe electrodeposition of polypyrrole–phosphate (PPy–P) and polypyrrole–tungstenate (PPy–W) on mild steel (MS) were achieved in an oxalic acid medium with cyclic voltammetry techniques. Adherent and homogeneous PPy–P and PPy–W films were obtained. The corrosion behavior of mild steel with phosphate (PPy–P) and tungstenate (PPy–W) composite coatings in 3.5% NaCl solutions were investigated through a potentiodynamic polarization technique, open‐circuit potential–time curves, and electrochemical impedance spectroscopy (EIS). On the basis of a physical model for corrosion of mild steel composites, Zview (II) software was applied to the EIS to estimate the parameters of the proposed equivalent circuit. It was found that the PPy–W coatings could provide much better protection than the PPy–P and polypyrrole coatings. The effects of the phosphate and tungstenate process parameters on the morphology and structure of the passive films were investigated by scanning electron microscopy and electron dispersion X‐ray analyses. The results reveal that the PPy–P and PPy–W coated electrodes offered a noticeable enhancement in protection against corrosion processes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Corrosion protection of mild steel by polypyrrole phosphate composite coating

Electrodeposition of polypyrrole phosphate (PPy–P) on mild steel (ST 12) was achieved in oxalic acid medium using cyclic voltammetry (CV) technique. Adherent and homogeneous PPy–P films were obtained. The corrosion behavior of mild steel with phosphate (PPy–P) coatings in 3.5% NaCl solutions was investigated through potentiodynamic polarization technique, open circuit potential–time curves, and electrochemical impedance spectroscopy (EIS). Based on a physical model for the corrosion of mild steel composite, the Zview (II) software was applied to the EIS to estimate the parameters of the proposed equivalent circuit. It was found that the PPy–P coatings could provide much better protection than PPy. The effect of phosphate on the morphology and structure of the passive film was investigated by scanning electron microscopy and electron dispersion X-ray analysis (EDX). The results reveal that the PPy–P coated electrode provided a noticeable enhancement of protection against corrosion process.

Use of poly(o‐toluidine)/ZrO2 nanocomposite coatings for the corrosion protection of mild steel

AbstractThis study explored the possibility of using poly(o‐toluidine) (POT)/ZrO2 nanocomposite coatings for the corrosion protection of mild steel in a chloride environment. POT/ZrO2 nanocomposite coatings were synthesized on steel substrates through an electrochemical route. These coatings were characterized with cyclic voltammetry, ultraviolet–visible absorption spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy. The performance of POT/ZrO2 nanocomposites as protective coatings against the corrosion of mild steel in aqueous 3 wt % NaCl was evaluated with the potentiodynamic polarization technique and electrochemical impedance spectroscopy. The results of this study demonstrate that POT/ZrO2 nanocomposite coatings provide better protection for mild steel against corrosion than pure POT coatings. The corrosion potential was about 0.312 V versus a saturated calomel electrode, more positive in aqueous 3 wt % NaCl for the nanocomposite‐coated steel than the uncoated steel, and the corrosion rate of steel was reduced by a factor of almost 51. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Electropolymerization of 2-Methoxyaniline: Kinetic Studies, Mechanism, Characterization of the Polymer and Applications as Corrosion Protection for Mild Steel in Acid Medium

Electropolymerization of 2-methoxyaniline on platinum electrode in acid medium was carried out under different reaction conditions as temperature, current density, hydrochloric acid, and monomer concentrations with reaction duration time. The initial rate of the electropolymerization reaction is small and the orders are found to be 1.18, 1.25, and 0.88 with respect to current density, HCl, and monomer concentrations, respectively. The apparent activation energy (Ea) is found to be 56.87 kJ/mol. The obtained polymer films are characterized by 1H-NMR, elemental analysis, and IR spectroscopic studies. The mechanism of the electropolymerization reaction has also been discussed. The thermogravimetric analysis (TGA) was used to confirm the proposed structure and determination of the number of water molecules associated with each polymeric chain unit. X-ray and scanning electron microscopic analysis were used to investigate the surface morphology. The corrosion behavior of uncoated and coated mild steel electrode with poly (2-Methoxyaniline) in 1 M HCl at 25°C was investigated potentiodynamically. The various electrochemical parameters (Icorr, Ecorr, and P%) were calculated from Tafel plots for uncoated and coated electrodes. The influence of some coating conditions as duration time, current density of the electropolymerization, and monomer concentrations were investigated. The data reveal that the presence of coated polymer films on the electrode surface increase the cathodic and anodic polarization compared to the uncoated sample.

Polyaniline for corrosion prevention of mild steel coupled with copper

Polyaniline emeraldine base/epoxy resin (EB/ER) coating was investigated for corrosion protection of mild steel coupled with copper in 3.5% NaCl solution. EB/ER coating with 5–10 wt% EB had long-term corrosion resistance on both uncoupled steel and copper due to the passivation effect of EB on the metal surfaces. During the 150 immersion days, the impedance at 0.1 Hz for the coating increased in the first 1–40 days and subsequently remained constant above 10 9 Ω cm 2, whereas that for pure ER coating fell below 10 6 Ω cm 2 after only 30 or 40 days. Immersion tests on coated steel–copper galvanic couple showed that EB/ER coating offered 100 times more protection than ER coating against steel dissolution and coating delamination on copper, which was mainly attributed to the passive metal oxide films formed by EB blocking both the anodic and cathodic reactions. Salt spray tests showed that 100 μm EB/ER coating protected steel–copper couple for at least 2000 h.

Electrocopolymerization of a binary mixture of pyrrole and 2‐amino‐4‐phenylthiazole: Kinetic studies, copolymer structure, and applications as corrosion protection for mild steel in acid medium

AbstractElectrochemical copolymerization of a binary mixture of pyrrole and 2‐amino‐4‐phenylthiazole on platinum electrode in acid medium was carried out. The kinetic parameters were calculated using ex situ microgravimetric and electrochemical data. The experimentally obtained kinetic equations were RP,W = kW [acid]1.16 [monomer]1.85 from microgravimetric data and RP,E = kE [acid]1.1 [monomer]1.9 from the values of the anodic current density using cyclic voltammetry technique. The apparent activation energy was calculated by the two techniques and is found to be 32.55 and 29.6 kJ/mol from microgravimetric and electrochemical data respectively. The monomer reactivity ratios (r1 and r2) were calculated according to Fineman–Ross method and the copolymer structure was determined from the obtained data, which is found to be a block copolymer structure. The applications of the prepared copolymer as corrosion protection of mild steel in acid medium are studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4047–4058, 2007

Protection of mild steel corrosion with Schiff bases in 0.5 M H 2SO 4 solution

Three new Schiff bases, viz., N, N′-ethylen-bis (salicylidenimine) [S 1], N, N′-isopropylien-bis (salicylidenimine) [S 2], and N-acetylacetone imine, N′-(2-hydroxybenzophenone imine) ortho-phenylen [S 3] have been investigated as corrosion inhibitors for mild steel in 0.5 M H 2SO 4 using Tafel polarization and electrochemical impedance spectroscopy (EIS). The three Schiff bases function as good inhibitors reaching inhibition efficiencies of ∼97–98% at 300 ppm concentration. The fraction <theta> of the metal surface covered by the inhibitor is found to increase with inhibitor concentration. Of the three Schiff bases, the S2 shows better efficiency than the other two Schiff bases. The adsorption of the inhibitor follows Langmuir isortherm. Thermodynamic calculations indicate the adsorption to be physical in nature.

Kinetics of the mild steel corrosion protection by polypyrrole-oxalate coating in sulfuric acid solution

Kinetics of the mild steel corrosion protection in 0.1 mol dm −3 H 2SO 4 by polypyrrole coatings have been investigated by the means of electrochemical impedance spectroscopy (EIS), cyclic voltammetry, polarization measurements and linear polarization. It has been concluded that during the initial time of immersion the coating resistance parameters increase which was connected with diffusion controlled dedoping of oxalate anions, simultaneously with hydrogen evolution reaction on polymer and dissolution of iron through polymer pores. Dedoping of oxalate anions from the bulk of the polymer decreases the polymer conductivity which provokes decrease of overall corrosion rate. After ∼40 h, the completely dedoped PPy coating acts as a classical polymer.

Corrosion behavior and thermal stability of electrodeposited PANI/epoxy coating system on mild steel in sodium chloride solution

The corrosion behavior, sorption characteristics and thermal stability of epoxy coatings electrodeposited on mild steel (MS) and mild steel with electrochemically deposited polyaniline (PANI) film were investigated in 3% NaCl solution using electrochemical impedance spectroscopy (EIS) and thermogravimetric analysis (TGA). Electrochemical deposition of PANI film on mild steel was performed from aqueous solution of 0.5 M sodium benzoate and 0.1 M aniline at constant current density of 1.5 mA cm −2. Epoxy coatings on mild steel and mild steel with PANI film were deposited at constant voltage. It was shown that during initial time of exposure to 3% NaCl, PANI/epoxy coating system on mild steel has lower values of pore resistance (obtained from EIS), greater amount of absorbed water and lower thermal stability (obtained from TGA) which indicate more porous structure comparing to epoxy coating on mild steel. During prolonged exposure to 3% NaCl, PANI/epoxy coating system exhibited increased corrosion protection of mild steel comparing to epoxy coating due to the barrier effect of PANI film and the influence of the dissolved molecular oxygen on cathodic and anodic reaction. Differences between corrosion behavior of epoxy coated and PANI/epoxy coated mild steel in acid and neutral solutions has been discussed.

Comparison between polyaniline‐phosphate and polypyrrole‐phosphate composite coatings for mild steel corrosion protection

AbstractPolyaniline, polypyrrole and their composites have been deposited on mild steel electrode from aqueous oxalic acid solution by using cyclic voltammetry (CV) technique. The resulting coatings were characterized by scanning electron microscopy and EDX analysis. The protective performance against corrosion of these coatings is evaluated by using electrochemical impedance spectroscopy (EIS) technique in corrosive solution (3.5% NaCl). Impedance data indicates a noticeable enhancement of protection against corrosion processes. Also, comparison of polyaniline‐phosphate and polypyrrole‐phosphate coatings indicates better corrosion protection with polyaniline‐phosphate coatings.

Corrosion behavior of duplex polyaniline/epoxy coating on mild steel in 3% NaCl

The corrosion behavior and thermal stability of epoxy coatings electrodeposited on mild steel and on mild steel with electrochemically deposited polyaniline (PANI) film were investigated by electrochemical impedance spectroscopy (EIS) and thermo gravimetric analysis (TGA). The aim of the paper was to present new findings on the corrosion protection of mild steel by a duplex PANI/-epoxy coating in 3% NaCI solution and to determine the effect of thin PANI film on the protective properties of the coating. PANI film was deposited electrochemically on mild steel from an aqueous solution of 0.5 mol dm"3 sodium benzoate and 0.1 mol dm"3 aniline at a constant current density of 1.5 mA cm"2. Non-pigmented epoxy coatings on mild steel and on mild steel with PANI film were obtained by cathodic electrode position at constant voltage and stirring conditions. The resin concentration in the electrode position bath was 10 wt.% solid dispersion in water at pH 5.7. The applied voltage was 250 V, the temperature 26?C and the deposition time 3 min. It was shown that thin PANI film could be used to modify the surface of mild steel prior to epoxy coating deposition, due to the increased corrosion protection of a duplex PANI/epoxy coating comparing to an epoxy coating on mild steel in 3% NaCl solution.

Corrosion studies on electrochemically deposited PANI and PANI/epoxy coatings on mild steel in acid sulfate solution

The corrosion behavior of mild steel and mild steel covered by electrochemically deposited (a) polyaniline (PANI) film, (b) epoxy coating and (c) PANI/epoxy coating system in 0.1 M sulfuric acid solution were investigated by electrochemical impedance spectroscopy (EIS). Electrochemical deposition of PANI film was performed from aqueous solution of 0.5 M sodium benzoate and 0.1 M aniline at constant current density of 1.5 mA cm −2. Epoxy coatings on mild steel and mild steel modified by PANI film were deposited at constant voltage. It was shown that thin PANI film had provided good corrosion protection of mild steel in 0.1 M sulfuric acid solution, and could be used for modification of mild steel prior to epoxy coating deposition. The increased corrosion protection of mild steel by PANI/epoxy coating system in the same solution was obtained.

Corrosion Protection of Mild Steel by Formation of Iron Oxide Polybithiophene Composite Films

Polybithiophene (PBT) was freshly electrodeposited on platinum (Pt) and steel electrodes using cyclic voltammetry from 2,2′-bithiophene (BT), electrolyte and acetonitrile (AC). The electrolytes used were LiBF4, LiClO4, LiCF3SO3, Bu4NBF4, Bu4NClO4, or Bu4NCF3SO3. Black to red colored PBT films with metallic lustre were electropolymerized on Pt and steel electrodes with good adherence. The electrochemical properties and the surface morphology of the deposited PBT film depend on the type of ions used during the electropolymerization. It was found that the steel surface was covered with Fe x O y –PBT composite. The results are discussed on the basis of the structural and the electrochemical properties of the electrolyte ions. The presence of PBT–iron oxide composite on the steel surface causes a shift of the pitting potential (E pit) in the positive direction, indicating the inhibitive effect of PBT–Fe x O y composite on the chloride pitting corrosion.