Key takeaways
- ASTM B117 controls how the salt fog apparatus runs; it is not a pass/fail specification.
- Hours of salt spray cannot be converted directly into years of outdoor service life.
- Compare systems only with the same specimen, preparation and evaluation rule, and pair results with adhesion, thickness and cure evidence.
A statement such as “1,000 hours of salt spray” sounds decisive, but hours alone do not describe the specimen, damage criterion or actual exposure. Use the test as one controlled comparison, with a defined acceptance method.
What ASTM B117 controls
ASTM B117 specifies how to operate a salt fog apparatus and maintain exposure conditions. It is a laboratory practice, not a pass/fail specification for a particular powder coating. The purchaser must state the specimen, duration, inspection interval and acceptance criteria.
Ask whether a test used a flat panel or production part, which substrate and pretreatment were used, whether a scribe was introduced, and where corrosion or underfilm creep was measured. A result from one system should not be transferred to a different metal or preparation route.
- Panel or production part
- Substrate, preparation and coating layers
- Duration, scribe and failure definition
Why hours are not service life
Continuous salt fog differs from changing outdoor cycles of wetting, drying, UV, temperature and mechanical damage. A laboratory result cannot be converted directly into a guaranteed number of years outside. For a coastal installation, ask about edge design, trapped water, maintenance and the complete coating system, not just a headline hour count.
If comparative testing is important, test candidate systems using the same specimen geometry, preparation and evaluation rule. Document the exact method edition agreed in the contract.
Better RFQ wording: “Submit results for the specified system on the specified substrate, with the test method, specimen preparation and acceptance criterion.”
Pair corrosion exposure with other evidence
Film thickness, adhesion, cure and visual coverage address different failure modes. A coating that performs well on a test panel still needs appropriate application to real edges, welds and recesses. Request qualification evidence and production inspection separately.
Frequently asked questions
What does 1,000 hours of salt spray mean for powder coating?
On its own, very little. The result depends on the specimen, substrate, pretreatment, scribe, inspection interval and failure definition. Always request those details alongside the hour count.
Does salt spray testing predict outdoor service life?
No. Continuous salt fog does not reproduce outdoor cycles of wetting, drying, UV, temperature change and mechanical damage, so hours cannot be translated into guaranteed years.
What should a corrosion test requirement in an RFQ say?
Require results for the specified system on the specified substrate, with the test method edition, specimen preparation, duration and acceptance criterion.
Next step
Planning corrosion qualification for a new part?
Share the substrate, exposure and the test you are being asked to meet. We will help scope specimens and acceptance criteria before panels are made.
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