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MAO coating is a significant research topic to improve the corrosion resistance of Mg alloys, which are currently being received much attention. The majority of current research is centered on optimizing the pore structure of MAO coatings to improve corrosion resistance, but the bonding between the coating and the substrate has been neglected. In this work, MAO coatings with different porosity and adhesion strength were obtained in phosphate and silicate electrolytes at different voltages. The structure, chemical composition, and mechanical properties of MAO coatings were also analyzed by various means, and their corrosion resistance was tested by electrochemical metholds. The influence of porosity and adhesion on the corrosion resistance of the coatings was analyzed and their mechanism has been examined, which is beneficial to obtain longer corrosion resistance MAO coating. [Display omitted] • The corrosion failure progress and mechanism of MAO coating prepared in different electrolytes has been studied. • The key factors affecting the corrosion resistance of microarc oxidation coating has been studied. • Enhanced adhesion strength can improve the corrosion resistance of MAO coatings. [ABSTRACT FROM AUTHOR]

Hydrogen embrittlement in hydrogen pipelines can cause severe economic losses and safety hazards, thus research on efficient hydrogen barrier coatings is of great importance. In this study, a more efficient and easily operable non-covalent modification method was employed to modify carboxymethyl chitosan (CMCS) onto graphene oxide (GO), resulting in a significant improvement in the dispersibility and uniform distribution of GO in waterborne epoxy resin. Subsequently, a hydrogen barrier coating was prepared by incorporating the modified GO into waterborne epoxy resin. The influence of different doping concentrations on the coating performance was investigated. The basic properties of the coatings were characterized using macroscopic analysis, SEM, contact angle measurements, adhesion tests and electrochemical techniques. The corrosion resistance and hydrogen barrier effect was evaluated through electrochemical hydrogen permeation experiments. Results showed that The modified graphene oxide has good compatibility with epoxy resin. When the content of CGO was 0.25 %, the dispersion was best. the CGO coatings has some corrosion resistance with approximately 10 MPa adhesive force and 105 Modular value at the beginning of immersion. The CGO coatings significantly improved the hydrogen resistance of ×80 steel. The lowest hydrogen permeation current density was observed at 0.25 wt% CGO concentration, which indicated optimal hydrogen permeation inhibition capability. • The graphene oxide (GO) has been modified to CGO by carboxymethyl chitosan. • 0.25%CGO was best dispersed in the epoxy resins. • The CGO complex coating has some corrosion resistance. • The 0.25%CGO coating has superior hydrogen resistance performance. [ABSTRACT FROM AUTHOR]

The effects of multiwalled carbon nanotubes (MWCNTs) on the adhesion strength and corrosion resistance of the acrylic nanocomposite coatings were evaluated on Q235 substrates via pull-off tests and electrochemistry measurements (EIS, LEIS). Addition of MWCNTs to the acrylic resulted in an up to ∼50% increase in the adhesion strength. After 36 h of immersion in 3.5 wt% NaCl, the coating resistance of the native acrylic coating was 235.8 Ω cm 2 , whereas those of the nanocomposite coatings containing 0.5 and 1 wt% MWCNTs were 1.36 × 10 5 and 9.27 × 10 7 Ω cm 2 , respectively. LEIS analysis indicated that the addition of MWCNTs increased the adhesion strength and retarded the delamination. The results demonstrated the positive effects of the incorporation of MWCNTs on the anticorrosive ability of the coatings. [ABSTRACT FROM AUTHOR]

Corrosion and hydrogen damage cause problems to oil and gas industry equipment. FeS (sulfur-iron) compounds generated by H 2 S causes surface corrosion and covers the surfaces of the equipment where the extent of corrosion and hydrogen damage are influenced by these compounds. Different types of FeS compounds have different crystal structures, and there by influence their corrosion and hydrogen resistance. In this paper, single-structure pyrrhotite and pyrite were synthesized by hydrothermal method, which was controlled by controlling the temperature and Fe, S ratio. Their structures are hexagonal sheet and polyhedron respectively. The interfacial properties and hydrogen barrier properties of FeS were tested and the results show that pyrrhotite possesses anion selectivity. The electrochemistry shows low impedance modulus and high corrosion current density, which indicates low corrosion resistance. Pyrrhotite has the lowest hydrogen permeation current density and has good inhibition of hydrogen permeation ability. For the high impedance modulus and low corrosion current density pyrite possesses cation selective, which shows strong resistance to corrosion. However, its hydrogen permeation current density is high and hydrogen blocking effect is weak. • The hydrothermal method was used to obtain pure FeS. • The structures of pyrrhotite and pyrite are the same with FeS generated in H 2 S environment. • Pyrrhotite possesses anion selectivity and pyrite possesses cation selectivity. • The hydrogen barrier effect of pyrrhotite is better than pyrite. [ABSTRACT FROM AUTHOR]

Purpose: The impact of rolling on the performance of micro arc oxidation (MAO) coatings on ZM5 alloy has been underreported. The purpose of this study is to explore the correlation between rolling and the failure mechanism of MAO coatings in greater depth. Design/methodology/approach: The influence of rolling on the corrosion and wear properties of MAO coating was investigated by phase structure, bond strength test (initial bond strength and wet adhesion), electrochemical impedance spectroscopy and wear test. The change of the surface electrochemical properties was studied by first principles analysis. Findings: The results showed that the MAO coating on rolled alloy had better corrosion and wear resistance compared to cast alloy, although the structure and component content of two kinds of MAO coating are nearly identical. The difference in interface bonding between MAO coating and Mg substrate is the primary factor contributing to the disparity in performance between the two types of samples. Finally, the impact of the rolling process on MAO coating properties is explained through first-principle calculation. Originality/value: A comprehensive explanation of the impact of the rolling process on MAO coating properties will provide substantial support for enhancing the application of Mg alloy anticorrosion. [ABSTRACT FROM AUTHOR]

• The corrosion failure progress and mechanism of MAO coating has been studied. • The surface roughness affects the bonding strength of the MAO coating significantly. • The high surface roughness could dramatically improve the corrosion resistance of MAO coating. In this study, micro-arc oxidation (MAO) coatings were formed on ZM5 Mg alloy substrate with different surfaces roughness. Therefore, the influence of surface roughness on the corrosion failure progress and mechanism of the MAO coated ZM5 Mg alloy has been investigated. The microstructure, bonding strength, and corrosion resistance of the MAO coatings were studied by SEM, LSCM, bonding strength measurement, and electrochemical test. The results showed that the surface roughness affects the porosity and bonding strength of the coatings. While it had little effect on the thickness and chemical composition of the MAO coating. Due to the high surface porosity, the coating of the grooved sample had poor corrosion resistance in the initial immersion. But, after a long-time immersion, the grooved sample was still protected by the coating, while the smooth sample showed severe damage. The strong bonding strength between the coating and groove sample was the key factor for enhancing the corrosion resistance of MAO coated ZM5 Mg alloy. [ABSTRACT FROM AUTHOR]