Controlling the Salt Water Corrosion Performance of Magnesium AZ91 Alloy

In die cast applications, high purity AZ91 alloy has been shown to result in parts with salt water corrosion performance that is 10 to 100 times better than the standard purity alloy. Two major concerns with regard to the continued development of the alloy have been resolved in the work presented; the variable level and activity of the iron contaminant has been quantitatively related to the amount of manganese present in the metal, and it has been shown that alloy of properly controlled manganese content and contaminant levels can be permanent mold or sand cast to produce parts with salt water corrosion performance equal to that of die cast parts. Only the nickel tolerance of the alloy was significantly affected by the slower solidification rates involved.