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  for Metal Finishing since 1989
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White dot defect

Im a fresh graduate and just join a plating company. I was appointed at aluminium anodizing line. Recently we are having problem in our anozing line which are white dot defect and water mark. To prevent the white dot defect, we modified a new water rinse tank to make sure good water rinsing after anodizing process. The white dot reduced but still have. We couldn't find why water mark occur. I hope to get positive reply from you. Thanks

Kavitha Selvaraja
Assistant engineer - Selangor, Malaysia
2007

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2007

The water mark is because of dissolved solids in your water. You may have to go to RO water or DI water. Two other cures are using warm water and using an air jet or knife to blow off the excess water. This can be manual or automated, but consider safety in whatever you do.
The white dot may possibly be from the chemicals that you use or it may be from the quality of raw materials that you use. Much better rinsing action as in air agitation or mechanical agitation and longer time will help remove previous chemicals from pits. Be happy that they are not black spots which are almost always from the raw material.
Welcome to the joys of metal finishing.

James Watts
- Navarre, Florida