properties of anti-corrosion materials?

Answer 1

Anti-corrosion materials fall into two types:-

1) They insulate the base material from all corrosive elements.

2) They chemically sacrifice themselves so that they corrode instead of the base material.

Plastic coating falls into the first category, as it should "seal" the base material from anything corroding it.

Zinc coating of steel falls into the second category, as the zinc will corrode (oxidise) to save the steel. The zinc oxidises, leaving a slight charge imbalance on the object, which discourages oxygen from reacting with the base metal.

Ships are fitted with a "Sacrifical Anode" a lump of zinc (can't remember whether it's termed anode or cathode), which corrodes away, and is regularly replaced, to reduce corrosion of the steel hull.

Chrome plating of steel is an example of doing things backwards, it is used to prevent corrosion, but in fact the chrome chemically encourages corrosion of the underlying steel. You just don'e see the corrosion, as it is at the back of the nice shiny chrome surface. You may have noticed that old cars with chrome bumpers would often end up with a flaky bumper which had all but rusted away, held together by a skin of chrome.

Answer 2

Depends where you want to use it?
In sea water? Sympathy Table.
In concrete? Acid Resisting
In Bridges & Rust Resisting
Battle Ships Manganese Bronze
And so on.
Coatings various provide most solutions
Properties are to many and varied until you define its use and load condition including temperature.

Answer 3

Either the atoms are so well locked up in the molecules that they don't react with oxygen from the athmosphere (e.g. plastic), or they do react with oxygen, but the resulting oxidy forms a layer that is impenetrable (e.g. aluminium).