Searching for shop to powder coat aluminum die cast parts
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I am currently searching for a paint facility (preferably in eastern Canada) which has experience painting die cast aluminum housings made of alloy 360 or 383. Our application is outdoor telecommunication equipment.
Up to now we have used permanent mold castings on which a powder paint was applied. When tested per ASTM B117 [link by ed. to spec at TechStreet] (salt spray), survival of 1000 hours was no problem. Since we switched to die cast we cannot get past more then 360 hours. Can you offer any advice?
Regards,Paul Slusarczyk, Quality Assurance
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A. Have you tried Mil-T-704 [link by ed. to spec at TechStreet]? It supposedly covers treatment and painting for engineering equipment, and includes aluminum.
Q. We have just started a new project: powder coated aluminium, and since then we haven't been successful as the paint of the aluminium is peeling off. We think it's due the pretreatment process meaning the chemicals we have used but I still think there's more to it than that … any suggestions?nadira kumartunga
colombo, sri lanka
A. Dear Paul ,
The problem as we see is not in the painting.
What we feel is that the die castings have a greater degree of surface porosity which are entrapping contaminants / air just prior to the powder coating or painting . Subsequently when the components are stoved this air entrapped within the surface porosity would cause a blister or peeling off. Also, in some cases, the air entrapped is also a major cause for corrosion and hence the decrease in life on the salt spray test. Vacuum Impregnation can be used for the sealing of such micro porosities in castings . The process route followed is Vacuum Impregnation, followed by Alodining, Followed by powder painting . We feel that therefore, you should give a thought to the pretreatment of the components before the powder painting .
Regards and Good Luck ,Mr Saibal Sen & Mr Probal Sen
- Pune , Maharashtra , India
February 10, 2010
A. Your problem has a simple fix. I have powder coated many different metals, and because of the porous properties of aluminum (cast iron is another), the piece must be heated for several minutes then cooled, then coated. The heating (I heat at 450 °F for 15 minutes) pulls out and burns off all of the crap in the tiny cracks of the aluminum. After that, you won't even be able to blast off the powder coat. It will be on permanently. I am not a scientist, but I know what works.Scott Carson
- Logandale, Nevada
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