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topic 10820

Salt spray for anodized aluminum


Q. Dear Sirs:

I am searching for standards requirements of aluminum anodized parts on salt spray fog testing.

Thanks in advance,

Leonardo Della Mea
Instituto de Ensayo de Materiales - Facultad de Ingenieria - Universidad de la Republica - Montevideo,Uruguay


A. Leonardo,

Mil-A-8625 [link is to free spec at Defense Logistics Agency,]specifications refers to ASTM B117 [link by ed. to spec at TechStreet] for the salt spray requirements. The test is specified at 336 hrs with the 3"x10" test specimens. This is a very standard testing application.

Best of Luck.

Ira Donovan, M.S.F.
Kansas City, Missouri

April 25, 2013

Q. How long should black anodized (Type II, Class II) last in a medical environment, where the product could come into contact with Saline solution on a daily basis. If the product was tested and approved to ASTM B117 standards how long should the product last, i.e., days, months, years?


Kevin Donahue
- Oceanside, California, USA

First of two simultaneous responses -- April 29, 2013

A. The chloride in the saline solution will attack the seal, then the oxide, then the aluminum. The time to noticeable attack is a function of the strength of the saline, the temperature, and the pH - but days, not weeks. The aluminum people have been trying for years to sell aluminum anodized trays for autoclaving and sterilizing medical instruments, but, again, the temperature and high pH destroys the anodic coating.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina

Editor's note: Mr. Probert is the author of Aluminum How-To / Aluminio El Como

Second of two simultaneous responses -- April 30, 2013

A. Hi Kevin,

One of the mistakes many people make is to think that passing an ASTM B117 salt spray test represents some sort of real time life for the parts, unfortunately it is never that simple. The salt spray is a quality control test that tells you that the anodising is functioning as it is expected to do under controlled conditions.

The only real way to know how long anodised parts will last in a real time situation is to expose the parts to those situations, simulating the exact conditions that they will see. For your particular conditions of use it looks like some sort of cyclic test will be necessary, exposing the parts to the saline concentrations seen in use and any cleaning process the parts may go through for cleaning.

Brian Terry
aerospace - Yeovil, Somerset, United Kingdom

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