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Corrosion resistance of AZ91D mag alloy

We have an aluminum part that may encounter indirect splash in a wet chemical process. We are looking toward magnesium thixomolding of this part instead of machining aluminum to save costs. We need to know about magnesium alloy AZ91D resistance to corrosion from ACIDS. How does it compare to aluminum? We currently black anodize the aluminum.

Ryan Blaquiere
semiconductor industry - Kalispell, MT, USA
2004

Similar to aluminum, magnesium is rapidly attacked by all mineral acids except HF & H2Cr2O4. However, the presence of Cl ions will increase the rate of attack of even these acids. You should have the magnesium component coated. The newer anodizing processes work well for protecting magnesium, or you could use a suitable organic coating like epoxy. Organic coatings should be deposited over some type of pre-treatment for maximum resistance.

Toby Padfield
Automotive module supplier - Michigan
2004

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