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Is my chromate conversion system up to par?

December 1, 2008

My company is running a small conversion coat system to clean custom sheet metal parts. I have been challenged to make sure our system is yielding the result for which the system is intended, and if they are not, then to find out what processes should be put implemented to maintain an adequate system. We currently test PH and Temperature. I was hoping there was an alternative or short-cut to a full laboratory titration. Are there any simple kit, manuals or training videos out there? I could really use some help.

Jason Beasley
OEM -Chromate Conversion Finisher - Keystone Hts, Florida, USA

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First of two simultaneous responses -- December 3, 2008

Unless you are processing a huge amount of material, testing once a week by titration should be adequate, in addition to the testing that you are doing now. Contact tech services of the company providing your chemicals for their recommended testing. Typically this will be for chromate as they do not want to talk about the other materials in their product, for good reasons.
You really need to be doing salt spray testing of the parts or more probably on test panels per the appropriate spec. Note that tiny cabinets do not work as well as medium size cabinets. At least one cabinet maker will not guarentee the results from their small cabinets. The problem is with the fog generator and the distribution of the material and still meet the spec minimums for amount. Running a salt spray cabinet looks simple, but it requires routine maintenance to work well.

James Watts
- Navarre, Florida

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Second of two simultaneous responses -- December 3, 2008

You must control concentration, your vendor should furnish the titration instructions, if not, I can arrange for you a product that comes with titration instructions and telephone service (by me).

Yes, control pH also. lower with nitric acid, raise with ammonium hydroxide.

Clean, etch, and deox properly, do not drag contaminants into the chromate. Moderate air agitation. Normal; room temp, however, at least one vendor calls for heat to 90 or 95 F.

Chlorides over 50 ppm (tap water) is lethal; make-up with deionized water, especially in Florida.

adv.
Call me for more consultation, no charge for telephone service.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina