Experimental study of corrosion protection of a three-layer film on AZ31B Mg alloy

A composite three-layer film was prepared on AZ31B Mg alloy for corrosion protection by means of plasma electrolytic oxidation (PEO), self-assembled nanophase particle (SANP) and electroless nickel (EN) plating. Structure and corrosion protection were characterized by various analytical instruments and electrochemical methods. Experiment results indicated that the composite film consisted of compact EN plating and coherent bilayer film, which provided effective protection for Mg alloy against galvanic corrosion and long-term immersion corrosion.

► A coherent bilayer is formed by nanoparticles and plasma electrolytic oxidation film.
► A coherent bilayer has excellent barrier property.
► Galvanic corrosion of the three-layer film on Mg substrate is inhibited greatly.
► The three-layer film provides long-term immersion corrosion protection.