Characterisation and electrochemical evaluation of plasma electrolytic oxidation coatings on magnesium with plasma enhanced chemical vapour deposition post-treatments

Plasma enhanced chemical vapour deposition (PECVD) post-treatment with three different precursors is employed to improve corrosion resistance of plasma electrolytic oxidation (PEO) coated Mg. Surface morphology, chemical and phase composition are characterised by SEM, EDS, and XRD analyses, whereas corrosion resistance is assessed by electrochemical tests. PECVD post-treatments can significantly affect PEO coatings, resulting in sealed pores and multi-layered inner barrier structure. Depending on the precursor, this can have both positive and negative influence on the corrosion resistance of the PEO coatings. The PECVD post-treatment with hexamethyldisiloxane precursor significantly improves corrosion resistance of PEO coatings, providing the best corrosion protection of Mg.