Under anoxic conditions, the mechanism for corrosion requires a substitute for oxygen as the oxidizing agent in the redox reaction. For abiotic anaerobic corrosion, that substitute is the hydrogen ion produced in the dissociation of water and the proceeding reduction of the hydrogen ions into diatomic hydrogen gas. The anodic half-reaction involves the oxidation of a metal in aqueous solution into a metal hydroxide. A common reaction that represents this process is the transformation of solid iron in steel into ferrous hydroxide as visualized in the following overall redox reaction.
The ferrous hydroxide may be oxidized further by additional hydrogen ions in water to form the mineral magnetite (FeO) in the process called the Schikorr reaction. 
In general, the anaerobic corrosion of metals, such as iron and copper, occur at very slow rates. However, when in chloride-containing aqueous environments, the rate increases because of the introduction of new mechanisms with the addition of a chloride anions.