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The achievement of high corrosion inhibition performances by manipulating the molecular structure of organic substances has gained much attention in recent years. In this paper, POCl3 was synthesized and Cl atoms in phosphoryl chloride (POCl3) were replaced by aniline or phenyl hydrazine and their derivatives; the effect of the substitution on the corrosion inhibition performance for mild steel immersed in 1 M HCl solution was investigated. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) and ultraviolet-visible (UV–Vis) spectroscopy were used to determine the molecular structure of the synthesized organic substances. Electrochemical impedance spectroscopy (EIS) and polarization measurements were employed to investigate the corrosion inhibition performance of the organic molecules for the immersed mild steel samples in the acid solution. The obtained results indicated that the inhibition efficiency of the synthesized inhibitors was increased by increasing the molecular size of the organic substances as well as increasing the number of nitrogen and oxygen heteroatoms in the structure of the organic molecules. The maximum amount of inhibition efficiency of the synthesized organic inhibitors in this paper was obtained about 93%.

Nowadays, powder coating can be used for many application, especially for protection against corrosive environments. Powder coating is usually done with using an electrostatic device and spraying gun. With using this method, a thin film layer is created on the surface which can play decorative or protective role. In this paper, the effect of some factors such as size of powder, charging, voltage, air flow, gun distance, charge–to-mass ratio, feed rate, coating functionality, glass transition temperature (Tg), viscosity, catalyst, temperature and curing time on the coating properties and their influence on the coating were mentioned. In recent years, nano composite polymers have been considered severely. Coating properties are improved by adding nanoparticles such as clay, SiO2, TiO2 and Al2O3 to the polymer composition. These coatings are used for reducing the gas permeability, thermal stability, optical clarity and increasing the mechanical and corrosion properties of coatings also these coatings have high mechanical properties that can be pointed to its high abrasion resistance. In this paper, the corrosion properties and the effect of adding nanoparticles on the corrosion resistance properties of powder coatings have been investigated, also the mechanical properties of powder coatings were reviwed.

This paper investigates the effect of yttria (Y2O3) coating on high temperature oxidation behaviour of low alloy 9 Cr–1Mo steel. The superficial coating is Y2O3 was prepared for experimental investigation. The isothermal corrosion study of uncoated and coated specimens was carried out in air oxidation environment at 973 K for 8 h. The corrosion rate and reaction kinetics were studied and the post corroded scales were characterized in SEM, EDS and XRD. The results clearly indicate that Y2O3 coated specimen improves the high temperature oxidation resistance than uncoated specimens. The improvement of oxidation resistance in presence of Y2O3 coating can be attributed to the changed mechanism of scale growth from outer cation migration to inner anion migration and enhancement of scale adhesion with the substrate. Further, enhancement of scale adhesion with the substrate in case of Y2O3 coating also improves the oxidation resistance. The detail mechanism of the oxidation of Y2O3 coated and uncoated specimen is further discussed in this paper.

The influence of superficial CeO2 coatings on isothermal and cyclic high temperature corrosion behavior of 2.25 Cr-1 Mo steel in oxidation and sulfidation (SO2 + O2) atmosphere have been reported in this paper. The CeO2 coating of three different depositions rate (0.15 mg/cm2, 0.30 mg/cm2 and 0.50 mg/cm2) were prepared for experimental investigations. The isothermal corrosion study of uncoated and CeO2 coated specimens was carried out in SO2 + O2 environment at 973K for 150 hours. The results clearly indicate that CeO2 coated specimen improves the high temperature corrosion resistance than uncoated specimens. The post corroded CeO2 coated specimen shows reduction of scale growth and improved scale adhesion to the substrate. The cyclic corrosion study was also carried out in both coated and uncoated specimen in same environment at 973K for 100 h. The CeO2 coated specimens on thermal cycling also shows significant improvement of the corrosion resistance without scale cracking and spallations. In contrary, the uncoated specimen in both isothermal as well as cyclic environment shows higher corrosion rate along with scale cracking and spallations. The results of the reaction kinetics have been substantiated by post corrosion analysis of alloy/scales combinations by SEM and XRD. The details mechanism of the corrosion in presence of CeO2 coating was further discussed in the paper.

Due to the directions and environmental legislations from RoHS (Restrictions of Hazardous Substances), WEEE (World Electrical and Electronic Equipment) and from various countries, lead is banned from alloy making. Lead free solder alloys thus become very popular in electronic package industries. The research people around the globe started searching for new lead free solder alloys which can replace the Sn–Pb alloy. Many lead free solder alloys were identified. SAC alloys were very popular among this. The presence of 3 and 4% of Ag content adds the cost as well as threat were detected in the medical devices due to electrochemical migration. Sn–1Cu–1Ni–1Ag is a promising alloy with good mechanical properties. The corrosion behavior of the Sn–1Cu–1Ni–xAg (x = 0, 0.5, 1% by wt.) was studied in this paper using 3.5% by wt. NaCl solution. Microstructure analysis, EDAX analysis was also done. The results show that the corrosion rates were decreased with the addition of Ag. The corrosion rates for 7 days and 14 days were almost same. Combining the mechanical properties and corrosion resistance, Sn–1Cu–1Ni–1Ag is a promising lead free solder alloy.

The paper presents the results of a study of the corrosion-electrochemical behavior of coatings based on the metastable phase of tungsten β-W obtained by chemical vapor deposition from fluorine-containing media in a neutral medium. It is shown that the corrosion nature of coatings based on β-W is fundamentally similar to that of the coatings based on α-W, but the β-W based coatings, due to a high stress state, show increased rates of corrosive dissolution.

—In this paper, chromate-free conversion coatings on aluminum alloys D16 and AMg3 are studied in a tropical marine climate. It has been shown that the conversion coating IFKhANAL-3 independently provides corrosion protection for aluminum alloy AMg3 for 9 months, and for alloy D16, for 6 months. Additional treatment with acrylate or PTFE varnishes makes it possible to increase this to 12 months or more.

In this paper, a small molecular complex {[Cu(2,3-Hpyza)] · 2(H2O)} (compound 1) was synthesized by solvothermal method from pyrazine dicarboxylic acid and Cu(H3COOH)2 · H2O. A metal organic framework (MOF) compound {[Nd2(2,3-Hpyza)3] · 4(H2O)}n (compound 2) was synthesized by solvothermal method from pyrazine dicarboxylic acid and Nd(NO3)3 · nH2O. Weight loss method, electrochemical measurement technique, and scanning electron microscopy technique were used to study the corrosion inhibition behavior of compound 2 and compound 1 on copper in 1 mol L−1 HCl. At 25°C, compound 1 and 2 had the highest corrosion inhibition rate of copper was 91.4% and 87.5% with concentration of 0.5 mmol L−1, respectively. The corrosion inhibition performance of compound 2 was better than compound 1 on copper corrosion. Both compound 1 and compound 2 were adsorbed on the surface of the copper, and accorded with the Langmuir isotherm adsorption equation.

The paper presents the results of studying the mechanical and anticorrosive properties of coatings based on the metastable tungsten phase (β-W) obtained by means of low-temperature chemical vapor deposition from fluorine-containing media. Corrosion studies in a 5% aqueous solution of NaCl showed that the general corrosion rate of W-based coatings reaches the value of 60 μm/year. The positive correlation between the corrosion rate of coatings and their hardness indicates a significant effect of the stressed state of the coatings on their corrosion behavior.

AISI 316 L austenitic stainless steel is widely used in various sectors of the industry (chemical, petro-chemical industry, paper industry, nuclear engineering, dairy equipment and medical field) because of its good corrosion resistance and biocompatibility. In contrast to these superior properties, it has a low hardness and poor wear performance, thus, limiting its use in some areas of industry. As a result of progress in science and technology, the expectation of superior properties from materials has increased and the surface modification has become an important part of this development. Amongst many coating processes, Electro-spark Deposition (ESD) is a micro-bonding process that is used to deposit a stronger, more robust and durable coating layer on a metallic substrate. This method can also be used to repair damaged parts, tools or equipment or to extend the tool and equipment life. In this study, the surface of AISI 316 L stainless steel was coated with WC and Ti6Al4V by ESD method. Morphology and microstructure of the deposited layers were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Surface hardness distributions were determined with a micro hardness tester. XRD analysis revealed that Fe–α, Fe–γ, W2C, Cr–Ti, Al–Fe–Ti phases exist on the deposited layers. The wear behavior of the coated surfaces was carried out by ball-on-disc wear method using WC-Co ball bearing with a diameter of 8 mm for a sliding distance of 250 meters at a sliding rate of 0.3 m/s under a dry condition using a load of 5 N. Corrosion behavior of coated surfaces i.e. Tafel extrapolation and linear polarization methods were investigated for the duration of 1 h in the SBF (Simule Body Fluid) solution. Morphology of layers formed on steel surface was examined by SEM microscope. Wear tests showed that AISI 316 L stainless steel has a low surface hardness but wear resistant coatings improved this property. The wear rate of coated AISI 316 L stainless steel decreased by 3–10 times with respect to the type of coating. The electrochemical experiments showed that the expected improvement was not achieved due to the high corrosion resistance of AISI 316 L stainless steel. However, the weakness of the surface hardness was partly replaced by an acceptable compromise from corrosion resistance.

This paper introduces copolymers of aniline and o-anthranilic acid with different ratio of aniline/o-anthranilic acid (r = 1, 2 and 3) as novel corrosion inhibitors for stainless steel in high-corrosive media. The synthesized polymers were characterized by Fourier-transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–Vis) and X-ray diffraction (XRD) techniques. After optimization of the aniline/o-anthranilic acid ratio, the inhibition efficiency of the best copolymer was measured for stainless steel in 2 M HCl solution. Electrochemical methods including potentiodynamic polarization and electrochemical impedance spectroscopy were used in different concentrations of copolymer. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to study the surfaces of the steel after exposed to test solution. It was found that the aniline and o-anthranilic acid copolymer with r = 3 can prevent the penetration of corrosive species into metal surface as protective film on the metal surface by physical and chemical adsorption.

Cost reduction for fuel cell stainless steel bipolar plate (BPP)’s Au-coating requires in depth understanding of its corrosion behavior. To this end, this paper explores the degradation of the tensile properties of an Au-coated 316L stainless steel bipolar plate in a real fuel cell stack. 4 BPPs were randomly chosen and removed from a stack that had run for 1600 h and, along with 2 pristine BPPs, were subsequently tested for surface morphology and tensile properties. Results suggest that (1) Pristine BPPs have initial pinhole flaws on the surface, whereas corroded BPPs have punctate (on O2 side) and continual (on H2 side) corrosions. (2) The tensile ultimate elongation for a BPP significantly decreases after corrosion on both O2 and H2 sides. (3) The degradation of tensile properties is attributed to primary cell effect.

The aim of this paper was to investigate the formation of an amorphous phase in the coating structure due to reduction in porosity and improvement in corrosion resistance of Ti6Al4V alloy during PEO process. The effect of crystallization on the electrochemical corrosion behavior and surface property of Ti6Al4V coating fabricated by plasma electrolytic oxidation (PEO) technique, was investigated in 5 wt %HCl solution. The coating compositions and electrochemical behaviors were examined by X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS) and polarization tests. The results showed that an increase in the ionic strength of electrolyte had a direct effect on the crystal size, the lattice strain and corrosion resistance. An increase in lattice strain due to Ti–O–Si led to a reduction in coating adhesion and corrosion resistance. A significant effect in phase transformation for Titania in the PEO process was not only led to an increase in polarization resistance but also reduced the number and size of porosity.

The alloy coatings such as zinc–nickel are used to improve the lifetime of zinc sacrificial coatings. zinc–nickel alloy coating has a longer history than other zinc alloy coatings and is considered as the most corrosion resistive zinc alloy. One of the important properties of this type of coatings is the ductility properties of coated steel pieces; as after thermal treatment and shaping operations, the corrosion resistance is enhanced up to an optimal level. Because of such properties, this alloy is investigated in coating the pieces such as connecting bolts, brake system components, and fuel system. Resistance to heat, ultraviolet light, hydraulic fluids, and fuels are other characteristics of such coatings. The use of zinc–nickel alloy coatings is growing in the bolts and threaded parts industry. Since these coatings do not prevent galvanic corrosion in contact with aluminum, they are widely used in industries that deal with aluminum bodies. However, the zinc–nickel alloys are considered as the most expensive coatings. These alloys are coated both by acidic and alkaline baths that provide different coating properties. This paper reviews the studies conducted on zinc–nickel alloy coatings, analyzing baths and their properties, the effect of different parameters on electrodeposition, as well as Zn–Ni multilayer and composite coatings and their properties.

The cyclic potentiodynamic polarization technique is a method for evaluating the susceptibility of a metal to localized corrosion such as pitting and crevice corrosion. This paper provides the information to conduct the cyclic polarization test correctly and to help performing the interpretation of the polarization scan properly. The effect of critical parameters including solution resistivity, scan rate, point of scan reversal, aggressive ions, corrosion inhibitors, metastable pits, metallurgical variables, temperature, dissolution gases, pH, immersion duration and surface roughness on the cyclic polarization curve and results interpretation are discussed. Then a number of cyclic potentiodynamic polarization curves for common metals and alloys in prevalent environments are given.

In this paper a new procedure for the calculation of uniform corrosion current density is presented. The procedure is based on the following criterion: corrosion current and extent of anodic and cathodic areas are such that the entropy production rate is maximum. Experimental data for the reaction Fe(s) + HCl(aq) = FeCl2(aq) + H2(g), taken from literature, are used to test the new model. A comparison between corrosion current density calculated from weight loss measurements and current density calculated from polarization curves by means of the proposed model is carried out. The proposed model provides a better agreement, between Tafel line extrapolation and gravimetric measurement, in comparison to the mixed potential theory usually adopted.

The present paper has aimed at studying heat resistance, electrochemical behavior, and tribological characteristics at high temperatures of superhard (~48 ± 2 GPa), multilayered with a modulation period of 17–18 nm, and nanostructured (nc)AlN-(am)Si3N4/(nc)TiN coatings obtained with an ion-plasma vacuum arc. The heat resistance of the coatings studied in the temperature range of up to 800°C inclusive was mainly determined by the oxidation of their surface layers without the substrate intrusion. Having a high coefficient of friction from 0.6 at 20°C to 0.8–0.85 at elevated temperatures, the coatings are characterized by virtually no wear, which was confirmed by profilometry measurements of friction zones. The obtained results concerning electrochemical behavior indicate that the Ti–Al–Si–N coatings are highly efficient in the protection of a cutting tool from corrosion in both acidic and alkaline media.

Nowadays, self-healing coatings display high abrasion resistance and bond strength. Application of these coatings are reckoned the most common and the most economic method for restoration and protection against corrosion by which metal structures durability is enhanced. The major role of a self-healing hybrid coating in corrosion inhibition is to supply materials for controlling types of corrosion. In this paper, titania–Benzotriazole nanostructured coating has been applied to substrate Al 7075 by using the sol–gel process and immersion method. The bonds existing in the hybrid coating, structure and morphology and coating corrosion behavior have been studied using Fourier transform infrared spectroscopy (FTIR), GIXRD, atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) and impedance electrochemical test, respectively. The obtained results are indicative of generating a homogeneous, uniform, crack-free titania–Benzotriazole nanostructured coating associated with excellent optimization of corrosion resistance at 2.8% Benzotriazole.

In this paper, two major technical problems (growth defects and chromium content loss) encountering when cathodic arc evaporation physical vapor deposition (CAE-PVD) was used for deposition of stainless steel and their subsequent effects on corrosion behavior of the coating in 3.5 wt % NaCl solution have been investigated. Growth defects in spherical and needle-like shapes were the common defects that resulted from CAE-PVD of a stainless steel and played a major role in determining the corrosion behavior of the coating. The results showed a composition difference between the coating matrix (with ~11 at % Cr) and the growth defects, particularly needle-like ones (with ~15 at % Cr). According to SEM images, it seemed that the needle-like defects were passivated and were susceptible to pitting corrosion while coating matrix was corroded. The results also showed that the corrosion of the coating was influenced by two factors: building up micro-galvanic cells between the needle-like defects (as passivated regions) and both coating matrix and the spherical defects (as active sites). In addition, an intense localized corrosion (as micro-crevice corrosion) was observed around the growth defects.

In this paper, due to special properties of aerogels such as ultra-low density and hydrophobic nature of aerogels, this nanomaterial was used as anticorrosive pigments. Silica aerogel was dispersed in epoxy resin by using sonication method. The dispersion of nanoparticles were characterized by transmission electron microscopy. The anticorrosive properties of these coatings were investigated by salt-spray and electrochemical impedance spectroscopy methods in a 3.5 wt % NaCl solution. Impedance parameters showed a decrease in coating resistance over immersion time. Results indicated that epoxy coatings containing nano silica aerogel could significantly increase the corrosion resistance of composite coatings compared to those of pure epoxy and the highest value was obtained for 0.5% aerogel nanocomposite coatings after 160 days immersion. Pull off adhesion test showed the highest value of adhesion was related to coating containing 0.5% aerogel. According to salt-spray methods, it was found that the best results were obtained with coatings containing 0.5 and 1 wt % of silica aerogel.

In the paper, the results of wear and corrosion tests of the CrCN/CrN multilayer coatings, formed by cathodic arc evaporation on 42CrMo4 (AISI 4140) steel substrates are presented. The substrates were subjected to thermo-chemical treatment–nitriding with various nitriding potential. The results of nitriding were determined by XRD and the hardness profile in the samples cross-section. The morphology of thin coatings was examined with SEM. A Vickers FV-700 and Fisherscope HM2000 hardness testers enabled to investigate hardness of steel substrates and CrCN/CrN coatings respectively. A pin-on-disc wear tests were used to determine the hardness and tribological parameters of the coatings: the coefficient of the friction and wear rate. The scratch test and Rockwell test were applied to assess the adhesion of the coatings to the substrates. The corrosion properties of coating–steel substrate systems were investigated using potentiodynamic polarisation tests. Corrosion potential, corrosion current density and polarization resistance were determined. It was found that that the nitriding of steel substrates improves properties of the coating–substrate system. The nitriding 42CrMo4 steel substrate with low nitriding potential enable to obtain substrates without surface “white layer” what favours good adhesion of the coating to the substrate. The CrCN/CrN multilayer coating–steel substrate systems show good mechanical and tribological properties and corrosion resistance.

Multiwalled carbon nanotubes (CNTs) were synthesized by catalytic pyrolysis of methane on iron-cobalt or cobalt-molybdenum catalyst and investigated by electrochemical and physico-chemical methods before and after chemical or electrochemical corrosion treatment. It is shown that CNTs have a higher corrosion resistance than does turbostratic carbon (carbon black) in corrosion testing under the same conditions. This is expressed in a smaller change in the amount of oxygen on the surface of the carbon material, the values of the electrochemically active surface area (EAS), and in significant differences of these quantities for the CNTs compared to carbon black. Quantitative comparison of the results of chemical and electrochemical treatment of CNT and carbon black, which was performed in this paper for the first time, leads to the conclusion regarding the advantages of corrosion testing by chemical method. Chemical testing simulates to a greater extent the long-term testing conditions of the supported catalysts composed of membrane-electrode assemblies of fuel cells in terms of evaluating the stability of the carbon material as a support of the catalytically active centers.

This paper introduces a novel coating process based on micro-arc oxidation (MAO) for formation of ceramic MgO layer over some newly developed magnesium alloys in an environmentally friendly electrolyte by anodization. Electrochemical corrosion testing showed that the corrosion resistance of bare AMS4429 is much better than that of AZ31HP-O and MZ due to formation of protective Nd-rich oxide layer in AMS4429 compared to less protective Al- and Zn-rich oxide films for AZ31HP-O and MZ respectively. Surprisingly, the corrosion resistance of MAO coated MZ is about 50 times higher than the bare one. The deposition, characterization and electrochemical characteristics of the fine porous MgO protective layer formed due to MAO coatings were investigated in details.

Ceria (CeO2) based high temperature coating was developed over 9Cr-1 Mo steel substrate. The coating is produced by plasma spray coating method by using robotic arm. Isothermal corrosion study of the CeO2 coated and uncoated specimen was conducted at 973 K for 8 h. The corrosion rate and reaction kinetics were studied and the post corroded scales were characterized in SEM, EDS and XRD. The results clearly indicate that ceria (CeO2) coated specimen improves the high temperature oxidation resistance than uncoated specimens. The kinetic behaviour of both coated and uncoated specimen follows approximate parabolic growth rate which further indicates that the corrosion is diffusion controlled growth. The post corroded scale of the coated specimen shows fine grained oxide scale with no scale cracking and detachment. The improvement of oxidation resistance in presence of CeO2 coating can be attributed to the formation of fine grained oxide on the scale, changed mechanism of scale growth from outer cation migration to inner anion migration and enhancement of scale adhesion with the substrate. The detail mechanism of the oxidation of CeO2 coated specimen and uncoated specimen is further discussed in this paper.

In this paper the process of the corrosion of the alloy 5083-H321 has been studied in 3% weight NaCl solution. We were interested in the effect of change in the physical state and chemical composition of the intermetallic particles on corrosion behavior of aluminum 5083-H321 alloy having undergone an annealing of 1h 30 min at 420°C, and having undergone the same annealing followed by various types of thermo-mechanical treatments. The results obtained show that the density of the intermetallic particles increases by 10 times and micropores are formed after the deformation by cold rolling. The distribution law of intermetallic particles changes after cold rolling. The morphology of corrosion changes also. The introduction of an intermediate annealing process during cold rolling of 1h at 250°C causes a recrystallization in the alloy but does not bring change on the corrosion morphology.

The surface of magnesium electrode was coated by immersing in phosphate, tungstate, molibdate and cerium solutions, after polishing with sand paper and abrading in 0.15 M HCl solution for 20 seconds. The corrosion of modificated magnesium with different compounds was investigated by electrochemical methods in 1 M NaCl solution. The results show that phosphate, tungstate, molibdate and cerium cations provide the corrosion protection for magnesium forming insoluble compounds on magnesium surface. The inhibition effect of protective layers prepared on magnesium surface were investigated by using potential-time, current-potential curves and Electrochemical Impedance Spectroscopy (EIS) spectra. The inhibition effect was calculated from corrosion rates and polarization resistance.