Can rust spread by contact?

Question

I just scoured a bunch of rust/corrosion off a metal tripod I left in my car trunk. There are still some tiny spots of rust on some of the connecting screws. If these spots touch (are screwed into) other, non-rusted metal, will the rust/corrosion spread by contact???

Answer 1

S.M.

Rust is a chemical compound- the term rust generally refers to iron Oxide that is formed when iron comes incontact with oxygen. The oxidation of iron occurrs more readily when water is present. The rust you left on your tripod doesn't spread--but any exposed metal parts made of iron (steel has iron) can rust.

I suggest that you paint the scoured parts.

Answer 2

I don't think so; rusting is a purely chemical process - oxidation - so it's not contagious.

Answer 3

no, but it must hav got wet tu rust.  keep it dri.  Look for leek.

Answer 4

Yes. The screws are probably a different alloy than the tripod.  Different metals have different degrees of electro-negativity.  Some tend to act as anodes and others as cathodes, in the presence of an electrolyte.  This is called Galvanic or dissimilar metals corrosion.  Ion migration due to this difference in electrode potential occurs when the metals are in contact and there is some kind of electolyte present.  Over long periods of time, rain can serve as a weak electrolyte, but acids, bases, and salt solutions work much faster.  This is why a sacrificial anode is used underwater with boats, to prevent metal parts of the motor from corroding other parts which might even be fairly far away.

Lead and zinc are interactive on this scale.  That is why they are used in car batteries.  Their difference in electronegativity is what causes the current to flow in one direction.  Of course, they corrode as this process takes place.  Even in a small amount of moisture, some metals corrode others very fast.  You might do a cool experiment by placing pieces of different kinds of metals against each other outside and see which ones corrode the fastest.  There will be significant differences between them. Try a piece of lead and a piece of zinc. (The surface of galvanized steel is zinc.)  Others of interest would be brass, iron, copper, and nickel.

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