Blast Media

We recently changed our blast media from steel to alumina. We now find that the blasted areas of the parts do not plate. We also find that if we skip the acid dip step the parts will plate okay. What’s going on?


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Q: We recently changed our blast media from steel to alumina. We now find that the blasted areas of the parts do not plate. The cycle we use is as follows:

  1. Soak clean
  2. Hydrochloric acid dip
  3. Electroclean
  4. Plate

 

We also find that if we skip the acid dip step the parts will plate okay. What’s going on? M. M.

 

A: I believe the alumina is the culprit in this problem. During the blasting step, some of the alumina becomes embedded in the surface of your parts. The alumina is soluble in both acids and bases and what is probably happening in your case is that the alumina is forming a gel that remains on the surface. A simple solution to this problem is to add a fluoride salt in the acid dipping step. The fluoride will react with the gel and remove it from the surface.
 

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