Rinse tanks generally foam due to cross contamination. Essentially, when you’re rinsing off the surfactant on your part, you’re dumping that surfactant into your rinse tank creating a low level of concentration inside of the rinse tank lowering the surface tension and creating foam. The best way to prevent foaming in a rinse tank is by chemical isolation aka setting up a small spray bar to pre-rinse the parts and either having that go to drain or feed back into the wash tank where we already have a sufficient surfactant concentration to create that cloud point.