Powder Coating / Teflon Coating /Anodizing on Aluminium Casting

Talk to your casting company and ask them. It sounds like some chemicals or parts of the casting process are leeching out of the aluminum, but the casting company should be able to tell you exactly what is happing.

The Hero is right. You and your supplier SHOULD both be concerned about the quality of your castings. You are partners in this. If they don't care, change vendors!

Does your part specification address surface contamination? Are your parts the only ones affected? I don't believe changing coatings will solve the problem.

Do uncoated parts display this condition, too? You could go to the expense of having the powder analyzed.

It was my experience that when I attempted colour anodizing of alloy aluminum the results were very unsatisfactory. On pure aluminum the results were very good. Alloying elements of the part seem to play an important role in the surface quality. Also the fastness of the colour largely depends on the quality of the dye. Instead of colour anodizing I would suggest the use of Chromic Acid anodising followed by black painting. For excellent long lasting quality epoxy based stoving enamel paint will be ideal.

dear all,

Thank you for your valuable feedback.

If anybody have different opinion, please suggest.

Please read relevant chapters of 'Anodising and Surface Finishing of Aluminum' by Wernick and Pinner.

http://www.amazon.com/Surface-Treatment-Finishing-Aluminum-Alloys/dp/0904477096/ref=sr_1_2/188-9653076-9207503?ie=UTF8&s=books&qid=1264061786&sr=1-2

Have a look at this recent thread, some of the comments there may be useful.