Review of Corrosion-Resistant Conversion Coatings for Magnesium and Its Alloys

TLDR

Magnesium alloys are highly susceptible to corrosion in humid and aqueous environments, limiting their use, and research is underway to find non‑toxic conversion coatings to replace hazardous Cr‑based systems. The study reviews the performance of several conversion coating technologies. The authors assess literature‑based performance and employ thermodynamic analysis to compare coating processes. Variability within a single coating technology exceeds differences between technologies, and pretreatment has a greater impact than the coating technology itself.

Abstract

Abstract The corrosion susceptibility of Mg and its alloys in humid and aqueous environments limits their widespread application. The performance of several conversion coating technologies is reviewed herein. In addition to the assessment of performance based on the literature to date, thermodynamic analysis has been used to compare coating processes. Ongoing research reveals that the search for appropriate conversion coatings to replace toxic Cr-based coatings continues. It is seen that the variability between coatings of the same technology was greater than the averages between coating technologies. Additionally, coating pretreatment also appears to be more significant than the choice of coating technology itself.