Influence of coating thickness on the galvanic corrosion properties of Mg oxide in an engine coolant

Magnesium is subject to severe galvanic corrosion attack in a commercially available engine coolant, when in contact with stainless steel and an Al alloy. Thin oxide coatings with different coating thicknesses were produced using a Plasma Electrolytic Oxidation (PEO) process to protect Mg against the corrosion attack. The galvanic corrosion properties of the PEO coatings were investigated using immersion corrosion testing. The test results showed that the anti-corrosion properties of the PEO coatings increased with increasing coating thickness. PEO coatings with a thickness of several micrometers effectively prevented the galvanic corrosion of Mg, without significantly reducing the heat conductivity of the Mg.