Pretreatment for Aluminum Castings

Ask an Expert From: Products Finishing, ,

Posted on: 12/1/2004

Question: You provide good, reliable advice and recommendations through the “painting clinic.” With respect to the question “Pretreatment for Aluminum Castings” in the Sept. 2004, Painting Clinic (www.pfonline.com/articles/clinics/0904cl_paint5.html), which addresses preparation of castings for powder coating, I’d like to take it a little further.

Question:

You provide good, reliable advice and recommendations through the “painting clinic.” With respect to the question “Pretreatment for Aluminum Castings” in the Sept. 2004, Painting Clinic (www.pfonline.com/articles/clinics/0904cl_paint5.html), which addresses preparation of castings for powder coating, I’d like to take it a little further. When powder coating aluminum components, folks need to remember that some powders require elevated temperatures for cure. These temperatures can approach or even surpass those used in heat treating the part in question during the coating process. Of course such a situation completely negates the temper that the part had prior to the powder coating process. Please be attentive to this. Thanks and keep up the good dissemination of knowledge. K. B.

Answer:

You raise a very important issue that I should have passed on to the readers. My company learned this aluminum temperature tolerance problem many years ago (when I had a real job). In the late 1950s, we were powder coating aluminum electrical conductors that had previously been insulated by hand taping and varnishing. Fortunately, our metallurgists advised us we were using preheat and curing temperatures very near the critical point for aluminum.

The message that K. B. and I want to convey is: “Before heating aluminum or any other substrate for industrial processing, determine its upper temperature limit and don’t overheat.”

 



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