Marine corrosion resistance of CeO2/Mg(OH)2 mixed coating on a low alloyed steel

Mixed Mg(OH)2/CeO2 coatings were deposited by cathodic electrodeposition on AISI 4135 steel in order to improve its resistance to marine corrosion. CeO2 coating was first prepared by cathodic electrodeposition in a low concentration of cerium nitrate bath. Then, brucite layer is formed by cathodic polarisation in magnesium nitrate bath. Scanning electronic microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and micro-Raman spectroscopy (μ-Raman) analysis were used to study the morphology, chemical composition, microstructure and thickness of the coatings. The corrosion resistance of the coatings was evaluated in artificial seawater by electrochemical methods. CeO2 coating presents a porous and cracked structure; consequently, it offers low corrosion protection of steel in seawater. However, Mg(OH)2/CeO2 mixed coatings have a more uniform and compact structure and present a better corrosion protection of steel in seawater. The protection efficiency of these coatings is then discussed and a protection mechanism is proposed after surface and cross-section SEM and μ-Raman analyses of the coating after several seawater immersion durations. [Display omitted] •Brucite layer improves the marine corrosion resistance of ceria coating.•Partial dissolution of brucite in seawater favors the deposition of CaCO3 layer.•Surface and cracks of mixed coating are filled by aragonite deposit.•The mixed coating acts both on anodic and cathodic reaction in seawater.•Rp of mixed coating increases continuously during its immersion in seawater.