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topic 5152

Adhesion Problem of Paint on Aluminum


We have been using a 6 stage washer for aluminum pre-treatment and spray painting for years.But recently the finished parts can't pass the adhesion test.We changed all the 3 bath of pre-treatment chemicals. The first 2 day adhesion test result is ok. But then problems happened again. Please help !

Jason Wang
- Shenzhen,China



One question. Is it casting aluminum ?. We have the same problem especially on high Si castings. We also have a solution to the problem if it is the same problem. Regards,

Jorgen Pettersson
- Sweden


Hi,Jorgen What we use is aluminum sheet.And it's been punched and bended into different parts. But if you can advise your solution,it will be highly appreciated. Best Regards Jason

Jason Wang
- shenzhen,China


Jason, I don't have an easy answer for you, but these questions might lead you down the right path.

If your cleaning/pretreatment chemicals have not changed, look for something that has. Has your water source changed? Are the parts made out of a different material? Are there new or different machining or cutting fluids on the parts? Release agents? These things may contaminate your baths/rinses and be redeposited on your parts.

You said you have changed your 3 chemical baths, how about your rinses? They may work with brand new cleaning tanks, the first two days, and then fail as the cleaning tanks become contaminated.

What did your concentrations

Kelly Draper
- West Plains, Missouri


Is the material that you are cleaning have any surface oils that are not water soluble? Is the adhesion coming off all over, is it continuous or spotty? You may have contamination on the material of some kind if you chemical levels and Ph are o.k.

Jack McGuire
- Indianapolis, Indiana

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