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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 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]