An AZ31 magnesium alloy coating for protecting polyimide from erosion-corrosion by atomic oxygen

Highlights: • AZ31 Mg alloy coating was deposited on Kapton substrate by magnetron sputtering. • AO erosion yield of AZ31 coating was about 34 times lower than that of Kapton. • No obvious morphology change was observed even after exposure to AO with a large fluence. • A MgO layer with trace amount of Al₂O₃ formed on the AZ31 coating resulted in its enhanced AO erosion resistance. - Abstract: A continuous and uniform AZ31 magnesium alloy coating was deposited by magnetron sputtering to protect flexible polyimide substrate (Kapton HN) from atomic oxygen (AO) erosion-corrosion in low earth orbit. The AO erosion yield of the coated Kapton was determined to be 8.87 × 10⁻²⁶ cm³ atom⁻¹ after exposure to AO fluence of 1.47 × 10²¹ atoms cm⁻², about 34 times lower than that of blank Kapton. XPS analysis results showed that an oxide layer of MgO formed on the surface of the coating after AO exposure, which is the main reason for the enhanced AO erosion-corrosion resistance of the AZ31 Mg-alloy coating.