Corrosion Resistance of Magnesium Alloys Processed by Equal Channel Angular Pressing

Corrosion resistance of Mg-5.5%Zn-0.6mass%Zr (ZK60) alloys processed by equal channel angular pressing (ECAP) was investigated using immersion tests and potentiodynamic polarization measurements in 5 mass% NaCl aqueous solution. The corrosion rates ECAPed ZK60 alloys increased by increasing number of ECAP passes. Potentiodynamic polarization curves suggested that cathodic reaction was activated, and a passive film formed during immersion tests was weakened by increasing ECAP passes. This can be due to increasing intermetallic compounds and dislocation density during ECAP process. For reducing dislocation density, heat treatment at 573K for 1.5h was performed. As the result, the corrosion rated od ECAPed ZK60 alloys were significantly reduced by the heat treatment.