Q: What salt spray result counts as a pass for zipper hardware?
A pass is defined by the specification, not by the absence of any change. Plated zinc parts commonly show white corrosion first and red rust later, so a specification usually allows a limited area of white corrosion at the end of the exposure and requires no red rust at all. Stainless and brass parts are judged differently, since they discolour rather than rust through.
Assessment should be done on a defined area under consistent light, with the percentage of affected area recorded and photographed. Note whether corrosion started at a cut edge, a scratch or a contact with the tape, because those indicate a different cause from a thin or poorly bonded plating. Compare against a retained reference sample so that judgements stay consistent between inspectors.
Acceptance requires the stated hours to be completed, the area limits to be met on every specimen, and the failure mode to be within the agreed list. A part that passes on area but shows red rust at a scratch has still failed if the specification prohibits red rust.