The role of Ca microalloying on the microstructure and corrosion behavior of Mg-6Zn-Mn-(0.5-2)Si alloys

Different amount of silicon and calcium additions have been carried out on Mg-6% Zn-0.5% Mn alloy and its effect on corrosion behavior is investigated. DC polarization and immersion tests were carried out on the extruded rods, which contain different amounts of silicon and calcium. Small amount of Si (0.5 wt.%) forms massive Chinese script Mg2Si intermetallics. Addition of 1 wt.% or more Si found to modify the Chinese script Mg2Si intermetallic into a fine polygonal shape. However, addition of Ca to Mg-6% Zn0.5Mn-0.5Si found to modify the Chinese script Mg2Si intermetallic into a fine polygonal shape. Improved corrosion behavior is noticed with the alloys containing Ca addition. The polygonal shape Mg2Si intermetallics inhibit the corrosion more effectively compared to the Chinese script. (C) 2009 Elsevier Ltd. All rights reserved.