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Powder paint salt fog test

2003

Good afternoon:

I'm the quality manager of a manufacturing company where we foundry aluminum and assembly cast iron and steel products, my design requirement for all of our products painted with powder coat or liquid paint is 2000 hrs Salt Fog test. I like to know what is the equivalence life in the environment for this test?. I already asked this question of our suppliers but I didn't receive any answer. I hope you can help me.

Thanks,

Esther Mendieta
- Brownsville, Texas

Hi Esther, The answer is simple. No correlation exists between performance in a salt spray test and performance in the real world.

George Gorecki
- Naperville, Illinois
2003

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Hi, Esther. To expand on George's correct answer, salt spray testing is not for predicting the life of a coating. Rather it is a QA measure to help you know if your process has gone south. If your process has been routinely producing parts that survived 2000 salt spray hours, and then one day they don't survive the 2000 hours, something has gone wrong and must be corrected.

To understand why you can't predict real life expectancy via salt spray testing, look at galvanized components as one example. They will last many decades in the real world because, as they begin to corrode, the zinc reacts with carbon dioxide in the air and forms very tight and impervious zinc carbonate coatings. But in "wet storage", where they can't "breathe" and react with sufficient carbon dioxide, they corrode quickly. A salt spray test is closer to "wet storage" than to decades of contact with the air.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
December 5, 2010