Modification of diatomite with PEDOT and CeO2 to construct Superhydrophobic bilayer composite coatings for high-performance anticorrosion of magnesium alloys

To effectively prevent the diffusion of corrosive ions from the external aqueous environment to the coating, as well as the permeation of ions from the coating into the underlying metal substrate, this study employed a simple spray coating method to construct a diatomite-based bilayer composite coating (referred to as OCDPD) on an AZ31B magnesium (Mg) alloy substrate. This OCDPD coating consisted of a bottom conductive polymer layer, which is a poly(3,4-ethylenedioxythiophene)-loaded diatomite/epoxy resin coating (PD), and a superhydrophobic top layer, which is an octadecyltrimethoxysilane modified CeO 2 @diatomite/epoxy resin coating (OCD). The as-prepared bilayer composite coating exhibited superior superhydrophobicity and self-cleaning capabilities, achieving a corrosion inhibition efficiency of 99.11 % after 168 h of immersion in a 3.5 wt% NaCl solution. Additionally, the OCDPD coating exhibited higher stability in salt spray tests compared to both single-layer coatings (OCD and PD). This study not only demonstrates the exceptional efficacy of the innovative composite coating in protecting Mg alloys from corrosion, but also provides a novel perspective on integrating conductive polymer coatings with superhydrophobic coatings as a comprehensive strategy for corrosion protection .