The salt spray test (ASTM B117 / ISO 9227) is the most common corrosion resistance test for plated fasteners. It evaluates how well a coating (like zinc plating) protects the base metal (usually steel) from rust in a corrosive environment.
Author: Marisa
The salt spray test (ASTM B117 / ISO 9227) is the most common corrosion resistance test for plated fasteners. It evaluates how well a coating (like zinc plating) protects the base metal (usually steel) from rust in a corrosive environment.
Purpose: Simulates accelerated corrosion in a salt-laden atmosphere (e.g., coastal or industrial areas).
Method:
Fasteners are placed in a closed chamber.
A 5% NaCl (salt) solution is misted at 35°C (95°F).
The test runs for a set duration (e.g., 24h, 96h, 500h).
Evaluation:
Time until white rust (zinc corrosion) or red rust (steel corrosion) appears.
| Plating Type | Unsealed Performance | With Chromate Passivation |
|---|---|---|
| Clear/Blue Zinc | 24–48h before white rust | 48–72h (ASTM B633 Type I) |
| Yellow Zinc (Chromate) | 72h before white rust | 96–144h (ASTM B633 Type II) |
| Black Zinc | 48–72h | 72–96h |
| Trivalent Chromate | 72–120h | 96–168h (RoHS-compliant) |