When I’m wet tumbling, after three hours it’s black water, so I have to clear water rinse about 2 times, then the 3rd rinse water I’ll add a 9mm case of citric acid to that rinse water, tumble 10 minutes and use that acidic water for my next wash cycle. I’m not a chemist but I stayed at a holiday inn once and don’t believe there’s a lot of moles to do any damage. This isn’t phosphoric acid. I read elsewhere there may be an advantage to this rinse step aiding in passivation. One last tip, if you do leave the acidic rinse in place, realize if your drying racks are a different metal, you may experience galvanic action. Good luck.