Characterisation and corrosion behaviour of plasma electrolytic oxidation coatings on high pressure die cast Mg-5Al-0.4Mn-xCe (x = 0, 0.5, 1) alloys

The results show that the growth rate of the coating is reduced, but the thickness is becoming more uniform if cerium is added to AM50 alloy. However, the phase composition and coating morphology are hardly influenced, but the corrosion properties reveal large differences suggesting that the porous PEO coatings have to be considered as a system of coating and substrate. A more uniform corroding substrate such as the cerium alloyed AM50 provides much better protection in combination with a PEO coating than the pure AM50. Flaking-off of large coating areas was observed due to the volume increase caused by corrosion products forming in the interface. Such a severe localised corrosion in the interface causing delamination of the coating can be suppressed by cerium addition.