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Will spargers/eductors reduce air agitation pollution issues?

We manufacture the External Tank for the NASA Space Shuttle program. The process includes chromate conversion coating of aluminum panels in 10,000 gallon open top dip tanks. We currently utilize air agitation with the tanks but are considering switching to liquid sparging to reduce chromate emissions. Are you aware of any documented studies that would help us estimate the potential emissions reduction.

Daniel S. Swords
- New Orleans, Louisiana

Recently, while employed by a manufacturer of liquid handling equipment in the surface finishing industry, I had occasion to write and present a paper at AESF Week on reduction of nickel emissions utilizing a form of pumped agitation. Although you really cannot create a theoretical analog between nickel plating and chromate conversion coating, I feel there should be cause for optimism in this approach. In nickel plating, the case history showed a reduction in nickel emissions up the stack from 0.30 mg/m3 down to 0.01 mg/m3. Since chrome has more of a tendency to mist, I would anticipate results at least as good. One of your colleagues at the location in Colorado is using the eductor [on eBay or Amazon affil link] agitation system to clean rocket tubes. I can't remember the man's name, but he was really pleased with the result.

Charles R. Reichert CEF-SE
surface finishing - Seattle, Washington

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