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White chalk like appearance on aluminium cargo containers

Hi

Can you please explain to the uneducated why we sometimes see a white chalk like appearance on aluminium?

(In this case the floors on refrigerated shipping containers)

natural atmospheric conditions or aggressive cargos?

Thank you!

Roger Austin
shipping - New Zealand
February 24, 2009

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First of three simultaneous responses --

I would would guess that the anodize layer had been compromised, and the raw aluminum is being attacked by the marine environment

George Brackett III
- Saco, Maine
February 25, 2009

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Second of three simultaneous responses --

Any number of reasons. Oxygen with a wet then dry floor might do it. Spilled material that was not neutral could cause etching. Temperature cycling may have an effect.

James Watts
- Navarre, Florida
February 25, 2009

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Third of three simultaneous responses --

Most aluminum corrosion compounds are white. Natural occurring aluminum oxide accelerated by condensation and salt air forms a white corrosion product. Powder coat is the best protection for the salt, chloride, varying temp exposure.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

February 26, 2009