Deposition, Characterization and Electrochemical Properties of Permanganate-Based Coating Treatments Over ZE41 Mg-Zn-Rare Earth Alloy

Rare-earth ZE41 alloy possesses unique mechanical properties. However, the sharp potential difference between the rare-earth phases (cathode) inside the Mg matrix (anode) results in building up micro-electrochemical cells and enhancing galvanic corrosion. In chloride solution, the galvanic corrosion propagates and enhances intergranular corrosion around the rare-earth phases. At the end, the rare-earth phase can be debonding from the matrix leaving holes. The optimum conditions for obtaining protective Mn-coatings of improved corrosion resistance for ZE41 alloy were determined. A simple one step surface treatment in 10 g/l Mn coating for short time was found promising to improve the localized corrosion resistance.