When acidic substances (including water) come in contact with metals, such as iron and/or steel, rust begins to form. Rust is the result of corroding steel after the iron (Fe) particles have been exposed to oxygen and moisture (e.g., humidity, vapor, immersion).

Where can rusting occur?

Rust occurs when iron or its alloys, such as steel, corrode. The surface of a piece of iron will corrode first in the presence of oxygen and water. Given enough time, any piece of iron will change entirely into rust and disintegrate. The process of rusting is a combustion reaction, similar to fire.

Where does rust occur in nature?

Most metals are susceptible to rusting. The only exceptions are rare metals such as gold, diamond, copper, bronze. Rust occurs whenever exposing metals to natural elements such as rain, sunshine, and air. These elements bring with them water, heat, and oxygen—paramount for rust to occur.