Refreshable self-polishing superhydrophobic coating on Mg alloy to prohibit corrosion and biofouling in marine environment

Abstract

Corrosion susceptibility is a critical obstacle for Mg alloy usage in harsh environments. Bioinspired superhydrophobic surface (SHS) affords a new way to combat corrosion. However, problems, e.g., water vapor condensation and air dissolution, ceaselessly hurdle practical usage of SHS for long-term corrosion inhibition. In this report, targeting the corrosion inhibition of Mg alloy in seawater, a refreshable self-polishing superhydrophobic coating is bound onto AZ31 Mg alloy bridging via a ceramic/paraffin buffer layer to solve the two problems encountered by traditional SHS. Firstly, the liquid paraffin is injected into the porous ceramic structure constructed by micro-arc oxidation (MAO). Then, carbon soot (CS) is grown onto the ceramic/paraffin layer via a combustion method. The internal CS layer is firmly bonded due to the molten paraffin. Meanwhile, the external superhydrophobic CS layer is soft and floppy to perform self-polishing property under dynamic water flow condition. The refreshable feature endows the regeneration of SHS. Using water jet flush (5.8 m/s) and immersion test up to 168 h, Mg alloy covered ceramic layer and carbon soot (MMAO-CS) coating demonstrates excellent stability. Using diatoms as target organisms to illustrate seawater anti-biofouling property, a few diatoms are found on MMAO-CS even after immersion for 10 d due to the low modulus and self-polishing of the external superhydrophobic layer invaded by the water phase and bio-organisms. For prohibiting corrosion in seawater environment, MMAO-CS coating possesses prominent resistance with |Z|0.01 Hz (2.82 ×107 Ω cm2) of 6 orders of magnitude larger than bare AZ31 (42.9 Ω cm2), enabling its potential usage in marine environment.