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Q & A: Metals that donít rust

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Q:
Which types of metals are mosst rust resistant? Steel zinc copper aluminium???
- Mandy (age 11)
11
A:

All of the metals you mention corrode. "Rusting" is a word which is reserved for iron oxidizing, but the other metals will also form oxides. There are many different kinds of steels, some which rust more easily than others. Stainless steel, for example, pretty much doesn’t rust at all, but it has significant amounts of other elements, usually chromium and nickel, in it.

Aluminum is fairly resistant to damaging corrosion, but it forms a thin oxide layer very quickly, which makes a hard barrier to prevent further oxygen from coming in to interact with the remaining aluminum. This is one reason why aluminum is a favorite in structural coatings (like aluminum siding on houses and aluminum screen doors -- they do not fall apart when they form a coating of corrosion). The thin oxide layer is enough to ruin electrical contacts, however, which is why it’s now illegal to make home electrical wiring from aluminum. Copper turns green or black when it oxidizes, and I think the zinc makes a white powder.

Other metals do not corrode easily or at all that I know of. Platinum and gold are very resistant to chemical attack of most kinds.

Tom (w mike)


(republished on 07/13/06)

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