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Brown effect on aluminum degreasing with an alkaline -- WHY?!

Can someone please tell me what might be the problem with the degreasing of aluminium (5052) sheets with an alkaline solution in the presence of temperature. The sheets come out with a brown stain that looks like a burn. This is new, it had never happened this frequently in the past please I need answers and solutions please help. please I need answers.

Anosike Okechukwu
- Cambridgeshire, United Kingdom
2006

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Hello Anosike,
The tech data sheet for the degreaser should have a pH range. Make sure the ph is not too high. Check the concentration of the degreaser as well. If the alkaline concentration is too high, you could be etching back the surface of the alloy. I have never been a big fan of alkaline cleaners or degreasers for Al or Al alloys. There are citric acid ⇦ this on eBay or Amazon [affil links] based degreasers out now that work very well. Good Luck!

Mark Baker
Process Engineer - Syracuse, New York
2006

Thanks for your reply on my earlier question. I have another enquire to make. I have a major problem now with the formation of smut on the surface of the degreased metal(AL). I would like to know what causes this effect is it that the alloys are reacting to the surface of the metal, or is it that the metal is etching and this leads to the smutty effect. No doubt the metal will etch but how do I stop this smut effect any ideas please any one

Anosike Okechukwu
cellbond composites - Huntingdon, United Kingdom
2007