Influence of uniaxial deformation on the corrosion performance of pre-coated packaging steel

The influence of uniaxial deformation on the corrosion performance of electrolytic chromium-coated steel (ECCS) in both the presence and absence of a polymer coating was studied using scanning electron microscopy (SEM), open circuit potential (OCP), potentiodynamic polarization (PP) measurements and electrochemical impedance spectroscopy (EIS). The individual and combined contribution of chromium-chromium(III) oxide and the polymer coating was investigated. Specimens were uniaxially deformed to maximum strains of 5, 10 and 25%, respectively. After deformation Lüders bands were observed on the surface of the metal substrates. The corrosion resistance of the ECCS was shown to be better than that of the bare steel, due to the protective properties of the chromium-chromium(III) oxide layer on the surface. The corrosion resistance of the ECCS was found to decrease with strain, to be attributed to the introduction of local defects in the coating leading to increasing exposure of the more active underlying steel with deformation. The PETG (a glycol-modified amorphous PET) coating as such proves to be a very effective barrier layer in protecting the underlying substrate, however, in combination with the bare steel its protective properties decrease with time of exposure and deformation. Combining the individual contributions of the chromium-chromium(III) layer and the PETG coating it was shown that the corrosion performance of the polymer-coated ECCS is significantly better than the polymer-coated bare steel after deformation, which can be also attributed to the good corrosion resistance of the chromium-chromium(III) oxide layers and the improved adhesion of the coating.     

Degradation of metal–polymer composite submitted to uniaxial deformations in 3.5% NaCl solution

This research evaluated the degradation performance of metal–polymer laminates. The material employed was an electrolytic chromium-coated steel (ECCS) sheet, protected by polyethylene teraphthalate (PET). This composite was submitted to uniaxial deformations simulating those occurring in the formation of containers. Later, it was electrochemically tested in 3.5% NaCl?w/v solution and characterised by scanning electron microscope (SEM). Finally, an evaluation of the degradation activity was made to determine the potential performance of the composite in canning applications. The results indicated that the deformation–degradation correlations of the layers depended on the plastic deformation, strain energy, surface quality of the PET polymer free from defects (with respect to a control sample), lack of continuity of the chromium oxide layer at the interface level due to the generation of microcracks, grain deformation in the metallic layers – both of ECCS and chromium layer – due to the generation of Lüder’s bands, loss of adherence detected by electrochemical tests and surface morphological changes of the protective polymer by uniaxial deformations.     

Corrosion behaviour of epoxy coatings electrodeposited on galvanized steel and steel modified by Zn–Ni alloys

The electrochemical and transport properties and thermal stability of epoxy coatings electrodeposited on hot-dip galvanized steel and steel modified by Zn–Ni alloys were investigated during exposure to 3% NaCl solution. Zn–Ni alloys were electrodeposited on steel by direct and pulse current. From the time dependence of pore resistance, coating capacitance and relative permittivity of epoxy coating, diffusion coefficient of water through epoxy coating, D(H₂O) and thermal stability, it was shown that Zn–Ni sublayers significantly improve the corrosion stability of the protective system based on epoxy coating. Almost unchanged values of pore resistance were obtained over the long period of investigated time for epoxy coatings on steel modified by Zn–Ni alloys, indicating the great stability of these protective systems, due to the existence of the inner oxide phase layer and the outer layer consisting of basic salts.     

Contribution of acoustic emission technique for monitoring damage of rubber coating on metallic surfaces: Comparison with electrochemical measurements

Chlorobutyl coatings are industrially applied on metallic inner walls of HCl storage tanks, in order to protect steel against corrosion. Rubber coating constitutes an efficient barrier against HCl penetration up to metallic surface; yet, traces of monochlorobenzene (MCB) into HCl solutions can locally damage the coating and induce both acid infiltration and rapid corrosion of steel under the coating. Acoustic emission (AE) technique, due to its non-intrusive feature and its sensitivity, is a potential technique for the detection of polymer coating damage as well as metallic corrosion under the coating. In that context, this technique was coupled and compared to electrochemical measurements at least for metal damage evaluation. AE signals produced by corrosion of bare metal in HCl solution were first characterized, and then AE and electrochemical results obtained during metal and/or coating damage were compared, in the case of physical or chemical deteriorations of the coating, in an HCl solution containing traces of monochlorobenzene. In case of physical coating damaging, AE and polarisation resistance measurements are in good correlation as soon as metallic corrosion starts. When polymer coating suffers a solvent impregnation, previously to HCl solution contact, acoustic activity increases as soon as corrosion under the coating occurs, whereas polarisation resistance measurements do not allow detecting corrosion of steel.     

Cerium acetate-modified aminopropylsilane triol: A precursor of corrosion-preventing coating for aluminum-finned condensers

A poly-acetamide-acetoxyl methyl-propylsiloxane (PAAMPS) polymer containing a cerium (Ce) oxide-derivative was synthesized through three spontaneous reactions: condensation, amidation, and acetoxylation. The PAAMPS synthesizing took place between the Ce acetate dopant and aminopropylsilane triol (APST) as the film-forming precursor aqueous solution at 150°C. PAAMPS was evaluated for use as a corrosion-preventing coating for air-cooled condensers consisting of two metal components: aluminum fins and carbon steel tube. The key factors to ensuring the maximum performance of the PAAMPS/Ce oxide coating system in mitigating the corrosion of both aluminum and steel included (1) minimizing the content of non-reacted water-soluble APST and Ce acetate remaining in the coating, (2) lowering the susceptibility of the coating’s surface to moisture, (3) precipitating a passive Ce³⁺ oxide (Ce₂O₃) film insensitive to Cl dissolution over the metal’s surfaces, and (4) possessing excellent adhesion to the metal’s surfaces. The combination of these factors considerably decreased the rate of the cathodic oxygen reduction reaction at the corrosion site of the metals. In fact, the corrosion rate, measured in milli-inches per year (mpy), of bare steel was reduced more than one order of magnitude by applying this coating. Correspondingly, the coating extended the useful lifetime of steel exposed in a salt-fog chamber at 35°C from only ∼10 hr to ∼768 hr. Furthermore, this coating system far better protected an aluminum substrate from the corrosion than it did one of steel. Even a very thin nanoscale coating film deposited on the aluminum’s surfaces reduced the corrosion rate, (mpy), by nearly two orders of magnitude over that of the bare aluminum. Also, the salt-spray resistance of aluminum panels covered by this nanoscale film was strikingly extended to more than 1440 hr, compared with ∼40 hr for bare aluminum. This program report, issued by the DOE Office of Geothermal Technologies, was performed under the auspices of the U.S. Department of Energy, Washington, D.C., under Contract No. DE-AC02-98CH10866.     

N80钢化学镀Ni—Fe—P的抗CO2腐蚀性能研究

采用腐蚀失重法和电化学测试方法评价了裸样N80油套管钢及其化学镀Ni—Fe—P防腐层的抗CO2腐蚀性能。结果表明，在抗CO2腐蚀方面，Ni—Fe—P镀层的腐蚀趋势比裸样的腐蚀趋势小，腐蚀电流密度和腐蚀速率低，即化学镀Ni—Fe—P试样的抗CO2腐蚀性能优于裸样的抗CO2腐蚀性能。     

Electrochemical and sorption characteristics and thermal stability of epoxy coatings electrodeposited on steel modified by Zn–Co alloy

The corrosion behaviour, transport properties and thermal stability of epoxy coatings electrodeposited on steel and steel modified by Zn–Co alloys were investigated during exposure to 3% NaCl solution. The electrochemical impedance spectroscopy (EIS), gravimetric liquid sorption measurements and thermogravimetric analysis (TGA) were used. Zn–Co alloys were electrodeposited on steel from chloride and sulphate baths, by different current densities. From the time dependence of pore resistance and coating capacitance of epoxy coating, diffusion coefficient of water through epoxy coating and thermal stability it was shown that Zn–Co sublayer obtained from chloride solution significantly improves the corrosion stability of the protective system based on epoxy coating. Almost unchanged values of pore resistance were obtained over the long period of exposure time, indicating the great stability of this protective system, due to the existence of a passive layer consisting of basic salts.     

Top coating of low-molecular weight polymer MALPB used for enhanced protection on anodized AZ31B Mg alloys

A protective composite coating on an AZ31B magnesium alloy was prepared by anodic oxidation to form an oxide layer, followed by single immersion in maleic anhydride-g-liquid polybutadiene (MALPB) solution to cover a polymer coating on top. As a low-molecular weight polymer with low viscosity, MALPB had a tendency to infiltrate into the pores and cracks in the anodic layer to fill the defects among oxides so that a compact layer could be formed after it was cured by its hardeners, as observed by scanning electron microscopy (SEM). This compact layer, which was composed of anodic oxides integrated with solidified MALPB, possessed thickness around 0.7 μm as detected by energy dispersive X-ray (EDX). The anodized, MALPB-coated AZ31B alloy exhibited enhancement in corrosion resistance superior to that separately coated by anodizing oxides or MALPB, as reflected by its much higher corrosion potentials (E _ccor) and lower corrosion current density (i _corr) in DC polarization tests. Based on electrochemical impedance spectroscopy (EIS) data, we conclude that the anticorrosive performance of the composite coating can be attributed to the barrier effects provided by different layers when the electrolyte passed through the MALPB layer, compact layer, and then the inner anodic layer before it reached the surface of Mg alloy, and that among them, the compact layer acted as a much more effective barrier to the electrolyte. The appearance of damaged areas on the composite coating surface after a much longer duration in a salt spray environment revealed that the life-span of the AZ31B Mg alloy could be greatly prolonged if the pores and cracks on the anodizing films were properly sealed by suitable polymers.     

Liquid metal corrosion resistant LaPO4 coating with metallophobic characteristics fabricated on 316 stainless steel using electrophoretic deposition technique

A liquid metal corrosion (LMC) resistant and metallophobic lanthanum phosphate (LaPO₄) coating was prepared on SUS316 stainless steel using electrophoretic deposition (EPD) technique. A specific hierarchical surface structure was created on coating surface by adjusting EPD process parameters. LMC test was performed using three different metal melts, Al–Zn–Mg alloy, Mg–Al–Mn alloy, and pure Zinc. Results indicated that steel bare surface was severely attacked by all three melts. The mechanism of corrosion process was explained in each case. After coating, the LaPO₄ covered steel showed an excellent resistance against all three liquid metals. Besides, wetting of steel surface by liquid metals was strongly decreased by application of LaPO₄ surface coating. This can be attributed to the intrinsic metallophobic characteristic of LaPO₄ as well as the hierarchical surface structure developed on coating surface.     

Green chemistry in situ phosphatizing coatings

The current organic coating on metals for aerospace applications involves a multi-step process and considerable energy, labor and control, and it generates toxic wastes such as chlorinated solvents, cyanide, cadmium, lead and carcinogenic chromates. The green chemistry technology of in situ phosphatizing coatings (ISPCs) developed in our laboratory is a one-step self-phosphating process, in which the deposition of metal phosphate layer on the substrate surface and the curing of polymer paint film take place independently, but simultaneously. The formation of a metal phosphate layer in situ will essentially eliminate the metal surface pre-treatment step of employing a phosphating line/bath. The use of chemical bonds linked to the paint polymers to seal the pores of metal phosphate in situ should enhance coating adhesion and suppress metal corrosion without a post-treatment of final rinses containing chromium (Cr⁶⁺). The successful applications of ISPCs in three types of commercial paints (solvent-borne high-solids, water-reducible and VOC-free latex) on bare and pre-treated cold-rolled steel and 2024 aluminum coupons is presented. The protective performance (coating adhesion and corrosion inhibition) of ISPCs is shown to be superior over that of the current multi-step coating practice.     

Development of novel waterborne poly(1-naphthylamine)/poly(vinylalcohol)–resorcinol formaldehyde-cured corrosion resistant composite coatings

Advancements in the field of corrosion protective coatings have headed towards the utilization of conducting polymer-based blends and composites for the formulation of corrosive protective paints and coatings. With the aim to develop an ecofriendly waterborne conducting polymer-based protective coating material, corrosion protective behavior of waterborne resorcinol formaldehyde (RF)-cured composite coatings of poly(1-naphthylamine) (PNA)/poly(vinylalcohol) (PVA) was investigated on mild steel (MS). The corrosion protective performance was evaluated by physicochemical, physicomechanical, corrosion protective efficiency and resistance in acid, alkaline and saline media by open circuit potential (OCP) measurements. The morphologies of coated, uncoated as well as corroded samples were analyzed by SEM technique. Superior corrosion protective performance was observed which was compared to the reported solvent-based conductive polymer coatings in different corrosive media.     

High-Temperature Oxidation Behavior of Solution Precursor Plasma Sprayed Nanoceria Coating on Martensitic Steels

Solution precursor plasma spray (SPPS) is used to deposit nanoceria coating on a 410 martensitic stainless steel. The process of pyrolysis in converting the cerium nitrate solution to cerium oxide, the microstructure and the surface chemistry is confirmed by thermodynamic calculations, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. Subsequent exposure of the coated steel in atmospheric air to cyclic oxidation at 1000°C revealed excellent corrosion resistance of the steel in presence of the SPPS-processed nanoceria coating. The formation of the nanostructured (10–100 nm) ceria coating is studied using transmission electron microscopy. Relative Ce⁴⁺ and Ce³⁺ concentration in the coating was determined from XPS high-resolution spectrum. Cross-section scanning electron microscopy showed the presence of an impervious nature of the protective layer with reduced scale thickness in the coated-oxidized sample. After a pre-oxidation treatment at 1273 K of the coated specimen, the oxidation kinetics showed a significant decrease as compared with the uncoated martensitic steel.     

Styrene butadiene co-polymer based conducting polymer composite as an effective corrosion protective coating

Electroactive conducting polymer composite coatings of polyaniline (PANI) are electrosynthesized on styrene–butadiene rubber (SBR) coated stainless steel electrode by potentiostatic method using aqueous H₂SO₄ as supporting electrolyte. The protective behaviour of these coatings in different corrosion media (3.5% NaCl and 0.5 M HCl) is investigated using Tafel polarization curves, open circuit potential measurements and electrochemical impedance spectroscopy. The results reveal that SBR/PANI composite coating is much better in corrosion protection than simple PANI coating. The corrosion potential of composite films shifts to more noble values indicating that SBR/PANI composite coating act as an effective corrosion protective layer.     

On the mechanism of the anodic protection of aluminium alloy AA5182 by emeraldine base coatings: Evidences of a galvanic coupling

Aluminium AA5182 coupons covered by a polyaniline film in the emeraldine base (EB) form showed increasing corrosion potential and decreasing corrosion current as a function of the thickness of the polymer layer. The cathodic reaction was proved not limited by diffusion of species inside the electrolyte solution and oxygen had no effect on the electrochemical behaviour of the coated samples. An EB coating on indium tin oxide conducting layer appeared slightly electroactive in neutral media. The IR spectra of aluminium coated samples, before and after heating in argon atmosphere, confirmed a redox reaction between the polymer film and the metal. This galvanic coupling can explain the good protective behaviour of emeraldine base against corrosion of aluminium.     

Semiconductive polyaniline melamine–formaldehyde blend electronic barrier to corrosion

Abstract

Polyaniline (PANI) is one of the intrinsic semiconductive polymers and shows some useful properties: high conductivity, transparency for the red and violet domain of spectrum, good elasticity and processability, superficial tension and chemical, photochemical and electrochemical behaviour. A PANI primer coat has been developed to act as an active electronic barrier to corrosion. When overlaid with a conventional durable topcoat, the coating has been shown to protect steel against salt, pollutants and other harsh environments.

Dry blends were prepared by blending the powders of doped PANI and the host polymer, a commercial melamine–formaldehyde resin AZAMIN M514 in a mixer. The hardness, elasticity, resistance and protective behaviour of melamine–formaldehyde resin films were determined. The protective behaviour of obtained melamine–formaldehyde resin blend was evaluated from quantity of Fe (II) released by the coated carbon steel samples (exposed area 1·0 cm^–2) immersed for 1 month in 50 mL 3·5%NaCl solutions. The prepared coatings protect substrate from corrosion by stabilising the oxide layer formed on the metal surface and thus prevent the metal dissolution process. An optimum formulation of melamine–formaldehyde resin coatings with 5 wt-% doped PANI exhibits good protective behaviour.     

Electrodeposition of poly(N-methylpyrrole) on stainless steel in the presence of sodium dodecylsulfate and its corrosion performance

Poly(N-methylpyrrole)-dodecylsulfate (PNMPy-DS) coating was electrosynthesized by potentiodynamic method on a stainless steel in oxalic acid solution containing sodium dodecylsulfate for the first time. The effects of electrochemical synthesis parameters, such as applied potential, scan rate and cycle number, on the protective behaviors of PNMPy-DS films were investigated and the optimum synthesis conditions were determined. The PNMPy-DS coating was characterized by the cyclic voltammetry, FT-IR spectroscopy and SEM methods. Corrosion protection behavior of this polymer-coated steel was investigated in 0.5 mol L⁻¹ HCl solution by potentiodynamic polarization and EIS methods. The results show that the PNMPy-DS coating provides effective protection for the stainless steel against to corrosion due to the fact that the large negatively charged dodecylsulfate dopant in the polymer structure electrostatically repels corrosive chloride ions and delays their access to metal surface.     

Complex anticorrosion coating for ZK30 magnesium alloy

This work aims at developing a new complex anticorrosion protection system for ZK30 magnesium alloy. This protective coating is based on an anodic oxide layer loaded with corrosion inhibitors in its pores, which is then sealed with a sol–gel hybrid polymer. The porous oxide layer is produced by spark anodizing. The sol–gel film shows good adhesion to the oxide layer as it penetrates through the pores of the anodized layer forming an additional transient oxide–sol–gel interlayer.The thickness of this complex protective coating is about 3.7–7.0 μm. A blank oxide–sol–gel coating system or one doped with Ce³⁺ ions proved to be effective corrosion protection for the magnesium alloy preventing corrosion attack after exposure for a relatively long duration in an aggressive NaCl solution.The structure and the thickness of the anodized layer and the sol–gel film were characterized by scanning electron microscopy (SEM). The corrosion behaviour of the ZK30 substrates pre-treated with the complex coating was tested by electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET), and scanning ion-selective electrode techniques (SIET).     

Drying and property studies on protective coatings formed by spontaneous surface polymerization

Drying studies on a protective coating formed by spontaneous polymerization on aluminum are described. The polymer coating studied here was formed from styrene, n-phenyl maleimide (NPMI), bismaleimide (BMI), and 2-(methacryloyloxy) ethyl acetoacetate (MEA). The coating successfully changed into an adherent film through drying in the presence of a coalescing solvent. Drying at a high temperature (> 170°C) enhanced the performance of the coating in terms of corrosion resistance and adhesion. It was found that the drying process involved removal of surface water on the substrate followed by formation of a dense protective layer associated with thermal crosslinking of g -diketone functional groups in the coating. The reaction mechanism, glass transition temperature, adhesion strength to aluminum, and corrosion resistance of these coatings are reported. The resultant coatings show excellent adhesion strength in a torsional test and very good resistance under the ASTM B-117 accelerated salt fog test.     

The mode of action of chromate inhibitor in epoxy primer on galvanized steel

Investigations of the mechanism of the protective action of strontium chromate pigment in an epoxy primer were carried out with electrochemical impedance spectroscopy (EIS), atomic absorption spectroscopy (AAS), scanning reference electrode techniques (SRET) and water uptake measurements. Epoxy primers applied to galvanized steel were studied in a corrosion environment which models the atmospheric precipitation of European countries. Corrosion and electrochemical properties of samples of bare galvanized steel and coated galvanized steel were investigated. It was established that the protective function of the chromate in the primer is primarily due to a cathodic/mixed inhibition of the surface of galvanized steel in defect areas of the polymer coating. It is suggested that the process of leaching of chromate ions from epoxy primer into the environment takes place because the decrease in pH at anodic defect sites causes the destruction of the primer film and accelerates the dissolution of the chromate pigment.     

Application of polyaniline/nylon composites coating for corrosion protection of steel

In this research, we investigated the corrosion inhibition properties of polished steel plates (low carbon) coated with a polyaniline (emeraldine base form) blend with nylon 66 (termed PANi/Ny) via cast method with formic acid as the solvent. Polyaniline (PANi) was prepared chemically from aqueous solution using aniline (0.2 M) as a monomer and ammonium persulfate (0.2 M) as an oxidant. The polymer powder produced was changed into emeraldine base (EB) form after treatment with dilute ammonia solution (0.5 M) in order to do further processing. The corrosion experiments were performed in the open circuit, exposing samples to different aggressive and corrosive conditions (e.g., NaCl, HCl). To produce a good comparison, the corrosion study was performed on both polymer-coated and bare-steel samples. Corrosion monitoring was performed by simple immersion tests and determination of the concentration of iron ions and metal weight loss in test solutions. It was found that PANi/Ny coatings can provide an anodic protection against corrosive environments in which the metals are exposed. The corrosion rate for the polymer coated steel was significantly lower than the bare steel (~10–15 times).