Superior corrosion- and wear-resistance of graphene oxide with the aid of composite silanes

Abstract

The practical application of magnesium alloy was limited greatly by the inherent poor corrosion- and wear-resistance. Herein, a composite coating composed of graphene oxide (GO), bis[3-(triethoxysilyl)propyl]tetrasulfide and octadecyltrimethoxysilane was prepared by spin-coating. Due to the cross-linking between silanes and GO, the so-obtained composite coating was more compact and less porous as compared with the coating of GO. The hydrophobicity was enhanced by the -S-S-S-S- moiety and high-density CH2 group in the silane chain; consequently, the so-obtained composite coating having the contact angle of about 140° was more hydrophobic as compared with the coating of GO (about 10°). Such a composite coating with higher hydrophobicity, denser siloxane networks and more compacter layered GO could slow down the permeation of corrosion medium and prolong the corrosion path. It was found that, compared to that of the Mg alloy substrate, the Ecorr of the composite coating increased by 713 mV and the icorr value decreased by nearly three orders of magnitude. Moreover, the composite coating possessed excellent wear resistance due to the intrinsic layered structure of GO and the good lubricity of silane.