There are many kinds of corrosion, which can attack metals, can cause leaks, explosions, fire, in equipment like pipelines and pressure vessels. But they also can cause cracks and embrittlement of metals used for construction. Corrosion is often identified with atmospheric rusting of iron base alloys, but that is only a subclass of one of the many possible mechanisms of corrosive attack.

Control method
Many metals and alloys have their own individual corrosion problem, but almost all of them are caused by liquid water (excepting high temperature corrosion of e.g. turbine blades) and the chemicals dissolved in it.

Each corrosion problem has its own cure (if any). Some corrosion can be controlled by electrical means (cathodic protection, CP) or the application of a non-metallic barrier e.g. a coating. Such barriers should be 100% pore free when used in highly aggressive liquid, and since this is rarely the case, they do not form a universal cure for metallic corrosion. Sometimes the metal generates its own barrier from corrosion products (e.g. metal oxide); the metal is then in the "passive condition". Another control method consists of adding certain chemicals to the corrosive liquid (corrosion inhibitors).

One of the most important methods is to find an economic alloy/environment combination where the alloy is in the passive condition and corrodes much less than carbon steel.

Non-metals like plastics,with and without fibre reinforment, and ceramics are mostly immune to corrosion. They are likely to replace metals in the future in many instances, but still are inferior to metals in many respects e.g. mechanical properties, joining techniques etc.

It is known that more than half of all corrosion problems could be avoided by direct application of established knowledge.