Where the
world gathers for metal finishing
Q&As since 1989


-----

Cold sealing of aluminum: crystals forming on tank walls

We have been using cold sealing for our anodised and coloured aluminum extrusions for the past 1 year and it seems to work fine with some occasional hiccups now and then. However of late we have some deposits of clear crystals forming on the sides of the sealing tanks. This crystals were also found at the bottom of the tanks as well. We fear that we may be overdosing our chemicals which may affect the sealing quality. Does anyone knows what could be the cause of this problem. Best Regards Elango

elango govin
Kemtec Sdn Bhd - Kuala Lumpur, Malaysia
1999

Cold/Low Temp seals tend to crystallize more so than mid/high temp seals. Its just a function of the seal from what I have read and been told by several companies that supply anodizing seals. The only way to determine if its having a degrading effect on your anodized parts is to do a test on a finished part. We use a specific dye for this purpose, its purple in tone and you either pour or immerse the part in it. You can then tell if the seal is not functioning properly by seeing if the purple tone remains on the part. If there is no residue on the part after immersion, you should be fine. Contact the supplier of your seal and ask them to perform this test or if they have a kit that you can do likewise with.

Matthew Stiltner
plating company - Toledo, Ohio
1999