Magnesium Treatment

Question:

We are a company that makes parts of aluminum as luminaries, car rearviews, TV tables, etc. We are mainly dedicated to making public lighting, so we have special interest in making luminaries with magnesium AZ91. The problem is that the parts are on the street and have to bear hard conditions of corrosion. We need 1,000 hours of corrosion resistance in a salt fog. Is there, at present, any treatment for magnesium for this kind of conditions? R.P.

Answer:

Do you need 1,000 hour performance for aesthetics or performance? Some plating alternatives may give you a functional coating, but may not hold up aesthetically for 1,000 hours. Some paint systems could possibly hold up to the 1,000 hours. An electrocoat with a powder topcoat may be capable of meeting these requirement. An epoxy electrocoat would give you the best corrosion resistance, while the topcoat would have to be something else such as an acrylic or polyester so that it would not fade in the outdoor exposure.

Finally, although I do not have direct experience with this, I have heard of people anodizing magnesium, similar to what is done for aluminum. A strong, hard anodic coating may also hold up well to these conditions.