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"Black spots after machining and white spots after cadmium electroplating on Al-7075 T6 material"

February 17, 2010

Sir, We have facing problems for aluminum 7075 T6 material as following :
1 ] Observing black spots after machining [especially in inner dia] on the components of aluminum 7075 T6 material.
2] Observing white spots after cadmium plating

Pl.suggest the cause of this defect & solution

Uday Deshpande
product designer - Pune, Maharashtra, India

February 17, 2010

Hi, Uday. Problems of this sort unfortunately do not often yield to a flash card question and a flash card answer.

Please first search the site for "black spots aluminum", where you will see a half dozen threads on the subject. After considering the previous answers provided, please try to frame your question in terms of those discussions to try to keep moving forward.

Similarly, there are a couple of threads about "white spots cadmium" which you can consider, and then build upon. Thanks and good luck.


Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

February 18, 2010

I will bet a cup of tea that your problem is caused by using the wrong coolant. for instance, the product Tap Magic is not intended for use as a cutting fluid, but lots of people use it on small jobs and it definitely will cause that kind of problem. The white spot after cad is probably caused by the black spot or a part that did not quite turn black. Talk to your cutting fluid vendor and get a cutting fluid that is designed for turning aluminum, and in particular, 7075.

James Watts
- Navarre, Florida

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