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Nickel-chrome plating of anodized aluminum grills

We are currently plating anodized aluminum grills. To remove the anodization from the grill we have been using a sodium hydroxide etch, then cleaning, and the standard nitric/zincate process upon which we plate in Bright Nickel and then chrome. Lately, we have been getting lots of speckles on the parts coming out of chrome causing them to fail. We assumed it was the etch just being old and replaced it but it appears to be in the Nickel tank, the perplexing problem is other parts plated out of that tank look great just the aluminum looks bad. Is it possible there is some strange reaction going on inside the tank with a possible drag-in of sodium hydroxide or some type of zincate contamination?
We have also been told to stop using the sodium hydroxide etch and switch to a mixture of 20-30g/l of chromic acid to 3-5% phosphoric acid (85%) at temp of 170-195 for 3-5 mins. Anyone else using this process and have better results than the standard hydroxide etch?

J. Giddings
Plating Shop - Hbg, Pennsylvania
2005

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I don't have any experience in actually doing that, J., but the chromic-phosphoric acid is indeed a recognized stripping solution--you'll find a number of letters about it by searching this website. As guesswork it seems to me that it will be a more satisfactory stripping solution for your situation than the hydroxide which, as I'm sure you know, attacks the aluminum substrate as well as the anodized coating.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2005