Hi Dan,
What I used was just regular laundry washing soda. 1 tablespoon per gallon. You can also use baking soda, but since I was going to use a lot of it, I went with the washing soda because it comes in larger boxes
I used 1/4 inch sheet PVC and then sealed it with silicone as I did not have access to a plastic welder.
I have also used this on a much smaller scale doing small parts in a 5 gallon bucket.
Here is the link to the original article.
http://www.stovebolt.com/techtips/rust/electrolytic_derusting.htmThanks,
Martin