Answer to Question #55353 in Physical Chemistry for Ojimi

Question

Is rusting a moderate reaction?

Answer 1

Rusting can formed quickly or slowly, depending on conditions (environment). Some things can extremely affect the rusting rate:
1) Humidity of air. In dry air rusting occurs slowly.
2) Medium. Presence of impurities such acids and salts leads to rusting accelerating in case of submerged iron.
2) Temperature - typically heat speeds up chemical reactions.
3) The electrical environment. If you have two different metals in electrical contact, and both in contact with salty water, then effectively galvanic element is made. Current flows, and the energy comes from the corrosion of the metals (zinc attached to iron corrodes first, protecting iron).
4) Presence of special additives – for example special stainless steel has nickel and chromium additives which bind to the iron atoms and keep them from oxidizing. The other example is painting or covering with oils.

There some other factors, so rate of rusting depends on conditions.