A salt-spray test exposes parts to a salt fog under controlled conditions for a set number of hours, following a method such as ASTM B117. It accelerates corrosion to reveal how a coating or metal surface holds up in a humid, salt-laden environment.

Manufacturers use it as a proxy for coating adhesion and durability claims. A powder-coated or PVD-coated surface that resists the fog for more hours is expected to hold up better in real use, though the test does not reproduce every real condition. It matters most for exterior coatings on tumblers and bottles exposed to condensation, dishwashers, and coastal air.

The number of hours a part is exposed, typically around 24 to 72 hours, is chosen to match the durability claim. Ask the factory which surface, which standard, and how many hours were used, since the answer is specific to a coating.

Practical takeaway: Tie the salt-spray hours to a written coating-durability requirement in your spec so the factory tests against a target, not a default.