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-----Red Rust Rating 6 or better, white Rust 2 or better
February 20, 2013
Q. This concerns an E-Coat and performance spec that the customer put on their print.
E-Coat WSS-M64J39-A1
Performance:
Must exceed 240 Hours Salt Spray Per ASTM B117
Red Rust rating 6 or better
White rust rating 2 or better
Where does the rating come from? I brought B117, M64J39, FITM BI103-01, and 3 others. Designation D1654 has a rating for failure for the scribe test, but I need to find rating for red and white rust? Do this exist?
- Auburn Hill, Michigan
A. Hi Nicholas. Very interesting question!
I've done some corrosion studies comparing various finishes, and then rated each finish from 1 to 9 for various factors. But when we did it, things were graded on a curve. For example, the best might be 9 (never 10 because something better could always come along). But in my case, we could not assign numbers except in comparison to the performance of other components.
If there is an objective rating scale I'd like to stop doing it wrong, but I'm not aware of such spec myself.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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February 21, 2013
February 22, 2013
A. Hi Nicholas,
In my experience, if you ask ten people how to run a salt spray test, you'll get twelve different answers. ASTM B117 is only good for specifying the test conditions.
I would ask the customer for his testing protocol. That's the only way to get to the bottom of it. There is no standard method for running the test and then rating the test pieces.
- Naperville, Illinois USA
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