Why rust occurs

The iron oxide typically has a reddish, flaky appearance that becomes progressively worse over time. If left unaddressed, the iron oxide will spread, thereby jeopardizing the physical integrity of the iron. Iron can rust from either exposure to air or exposure to moisture. Both oxygen and moisture are catalysts for rusting. When iron is exposed to air or moisture, oxidation will convert it into iron oxide. There are ways for metalworking and manufacturing companies to protect their iron workpieces from rusting.

Galvanization, for example, is a common anti-corrosion treatment process for iron. It involves the application of a protective coating over the surface of a metal workpiece. With galvanization, zinc is applied over the surface of iron. What Is Corrosion? How Corrosion Occurs Corrosion is an electrochemical reaction that appears in several forms, such as chemical corrosion and atmospheric corrosion, the latter of which is the most common form.

This is a corroded tank. Removing and Treating Rust Depending on the situation and application, you may be able to treat the area that has corroded. How Can I Prevent Corrosion? Left: A tank experiencing corrosion. It is an actual chemical change which takes place when metal starts to rust. Everything around us is made up of different chemicals. These chemicals are made up of atoms. The atoms can join together to create new chemicals.

The atoms can also join and make up chemical compounds. Rust is a chemical compound. The iron atoms fuse together with the hydrogen and oxygen atoms.

The formula for water is H2O. Adding the water creates a chemical reaction. The result can be seen as rust.

Left in a totally dry environment, iron or steel will not rust. It is when moisture is added that the oxidation process starts to occur. There is anodic dissolution or oxidation of iron going into aqueous water solution:. Cathodic reduction of oxygen that is dissolved into water also occurs:. The iron ion and the hydroxide ion react to form iron hydroxide:.

The iron oxide reacts with oxygen to yield red rust, Fe 2 O 3. Because of the electrochemical nature of the reaction, dissolved electrolytes in water aid the reaction. Rust occurs more quickly in saltwater than in pure water, for example.

Keep in mind oxygen gas O 2 is not the only source of oxygen in air or water. Carbon dioxide CO 2 also contains oxygen. Carbon dioxide and water react to form weak carbonic acid. Carbonic acid is a better electrolyte than pure water. As the acid attacks the iron, water breaks into hydrogen and oxygen. Free oxygen and dissolved iron form iron oxide, releasing electrons, which can flow to another part of the metal. Once rusting starts, it continues to corrode the metal.

Rust is brittle, fragile, progressive, and weakens iron and steel. To protect iron and its alloys from rust, the surface needs to be separated from air and water. Coatings can be applied to iron. Stainless steel contains chromium, which forms an oxide, much like how iron forms rust. The difference is the chromium oxide does not flake away, so it forms a protective layer on the steel.