nwinp

Topic: Coating Weight Analysis for Chromium Phosphate on Aluminum

I am writing to inquire about the determination of Coating weight for Chromium-Phosphate coating on Aluminum based substrates. I am looking for a gravimetry method with the use of an appropriate stripping solution. I have tried numerous stripping solutions, including alkaline and acidic type, and were found to be unsucessful. Either the solution was too aggressive and attacked the substrates, or the phosphates coating were found to be insoluble in it. I have also tried a few inhibitors along with it, but still no luck. Any recommended solution would be greatly appreciated. 


dpatterson

Re: Coating Weight Analysis for Chromium Phosphate on Aluminum

NWINP:

Each type of conversion coating will typically require a different type of stripping solution.  You mentioned chrome phosphate on aluminum.  I am assuming you are talking about the "green coating normally found on aluminum extrusions.  We perform coating weight tests on these pieces in our laboratory frequently and  utilize the following method.  This method has been around for years.  Typically we will do 3 or 4 readings and take the average.  You should make up a new bath every 10 to 12 extrusions.  Recently I have started drilling holes in the top of the extrusion and using aluminum wire to hang them over the side of the beaker.  That way the tongs never get in the molten salt bath and we do not have to "fish" for parts.  If you are looking for a procedure for the gold chromate conversion coating, I have that one as well.  I hope this helps you out.

dpatterson

A Brite Company

Attachments: Click Here to See


Attachments:

  Procedure for Determining Coating Weights on Aluminum.pdf

nwinp

Re: Coating Weight Analysis for Chromium Phosphate on Aluminum

Thank you for your prompt reply.

Although this procedure is a bit dangerous to work with, it shows reasonable results. I appreciate your help.

Nwinp