Metal finishing Q&As since 1989

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How many years of real life do 48, 96 or 192 Hr of Salt Spray Test equate to?

2004

Good Morning !

Please inform me how many actual years reflect a 48, 96 or 192 hours of Salt Spray Test according to ASTM ASTM B117.

Thank you in advance.

Bremer Chezi
Director Mechanical R&D - Tel-Aviv, Israel

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2003

There's no harm in asking, Bremer, but actually this question has been answered here many times before. Salt spray testing is solely a QA measure, used to make sure nothing has gone south in your process, it is not a prediction of real-world life. The only thing that can be said is that if the quality control on a particular finish is improved such that it gets better salt spray life, it will get as good or better life in the real world.

Corrosion mechanisms are different in an accelerated test cabinet than in real life. For example, finishes that build protective carbonate corrosion products in real life, build none in a salt fog cabinet. So if you were to compare, say, an anodized aluminum finish to an electroless nickel finish to a powder coated finish, to a nickel-chrome finish, to a zinc with chromate finish, it is entirely possible that one of these finishes that lasted only 48 hours in a salt spray cabinet might in the real world easily outlast a different finish that survived 192 hours of salt spray.

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

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There are a few instances where "B117" type test methods result in an inverse correlation with real world exposures. This could lead to a false 'pass' and result in poor selection of materials.

There may be some useful information at http://autotestreport.com/2000_Articles/0500_engineers.htm [Ed. note: this URL is no longer functional] in the May article by the editor, in which a steel company engineer (Ph.D., PE) relates many problems with salt fog (spray) tests when attempting to predict service life.

To 'prove' a lab test has correlation with real world exposures, there must be the same corrosion mechanisms and the same corrosion products from each, which means that real world exposures must be performed. It is a daunting task, but there are statistical-based Design of Experiment means to reduce the permutations of all variables.

Harold D. Hilton
material testing - Chicago, Illinois
2004

Performed Salt fog testing on mild steel parts which have been single nickel/chrome plated. They have performed very well in Salt fog setup to ASTM B117 standards but customer needs to understand how these salt fog hours [in this case 200] translate to his products life in the field in years of service. Is there any information I can reference or website with some good information on this?

Mark Pekovitch
Customer - Wheeling, Illinois
June 2, 2009