Pretreating Magnesium

Ask an Expert From: Products Finishing,

Posted on: 12/1/2002

Question: I have an inquiry for powder coating wrinkle finish to a magnesium casting.


I have an inquiry for powder coating wrinkle finish to a magnesium casting. I assume powder will take to mag but what pretreatment should I use for the alloy? B.O.


Two pretreatments common to magnesium alloys are a phosphate pretreatment and anodizing. Both provide a good base for paint and, depending on the specific process, may allow for additional corrosion protection. Cleaning magnesium and magnesium alloys should be done at an elevated pH, usually greater than 12. If done at a pH lower than that, it will result in attack of the magnesium surface.

Since you are going to powder coat these pieces, I would think you might be better able to handle a phosphate pretreatment system than the anodizing. Assuming you currently have some type of pretreatment for your current powder coated product, you should contact your current chemical supplier and let them know you will be introducing magnesium castings through the line. They will likely want to make some modifications to your cleaner tank (pH considerations mentioned above) and changes to the accelerators/activators in your phosphate system to make it multimetal compatible.


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