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Intermittant pitting after HAE magnesium anodise

March 18, 2010

Hello.

We have machined AMS4439 castings HAE anodized at a surface treatment supplier. On occasion, the parts have hundreds, if not thousands of tiny black indications of minimal depth. The part can also have short wormlike black indications of similar depth to the black dots.
If anyone has an idea as to the root cause of this intermittent deviation, it would be greatly appreciated.

Grant Morris
Manufacturing planner - Montreal, Quebec, Canada

Do you perform vacuum impregnation on the casting? I'm not 100% sure that is your problem, but I do know that impregnation addresses some of the problems associated with magnesium castings.

Jon Barrows, MSF, EHSSC
Kansas City
March 22, 2010

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