Corrosion performance of magnesium alloys MEZ and AZ91

The corrosion performance of sand cast MEZ(S), zirconium-grain-refined MEZ(R), sand cast AZ91(S), and high pressure diecast AZ91(D) magnesium alloys were evaluated by means of salt spray testing, optical metallography, hydrogen evolution, polarisation curve measurement and AC impedance spectroscopy. The results show that the corrosion resistance of the four alloys can be ranked in decreasing order as AZ91(D) > AZ91(S) approximate to MEZ(R) > MEZ(S) and that the intergranular phases and chemical composition of the matrix phase have a significant influence on the corrosion performance. Alloys with a finer grain size and higher aluminum or zirconium contents exhibit better corrosion resistance.