Electroless codeposition of GO incorporated silane nanocomposite coating onto AZ91 Mg alloy: Effect of GO content on its morphology, mechanical and corrosion protection properties

Abstract

The corrosion of Mg alloys is a significant concern in practical applications, and silane-based protective organic coatings are promising to protect the Mg alloys from corrosion. The (3-glycidyloxypropyl) trimethoxysilane/graphene oxide (GPTMS/GO) coating was developed using electroless codeposition technique on AZ91 Mg alloy such that GO sheets were grafted with silanol groups. The coating was prepared by dipping AZ91 Mg alloy in GPTMS/GO solution and then curing at 120 °C. The electrochemical measurement results showed an increased corrosion resistance of AZ91 Mg alloy in 3.5% NaCl solution. The decrease in the corrosion current density value of 0.016 µA cm−2 is attributed to the formation of a passive layer of GO grafted GPTMS on the surface of AZ91 Mg alloy. The enhanced hydrophobicity of 108°, the improved adhesion (5 A) and high hardness (52 HV) were attained due to covalent metallic siloxane bonds (MgOSi) and the laminate structure of GO developed on AZ91 substrate.