Corrosion is a change that takes place on the surface of a metal when it is oxidised. These metals could be in the smallest parts, such as in electrical wires, or large scale in the case of structural girders. It can be both a costly and dangerous occurrence, and there are a number of things that can be done to help protect the surface of a structure. One option is the use of HVOF from companies like Poetons, where a coating is placed on the outside of the metal to help prevent it from being affected by environmental factors and oxidisation.
There are some metals, such as copper, that develop their own natural defence against corrosion in the form of a bluey-green patina that appears on the outside of the metal. This actually protects the metal from being affected by corrosion. It is one of the reasons that this metal is used in plumbing and heating systems. Copper, however, is not suitable for heavy load-bearing as it bends and shapes too easily. Stainless Steel is another metal (an alloy) that is not affected by corrosion or the effects of oxidisation. Again is not suitable for all applications.
When corrosion of metal takes place, the metal begins to weaken, which in the case of structural elements can cause bridges and buildings to collapse. There are metals like copper mentioned above that have natural defences against the effects of corrosion and other metals like gold that seem to be unaffected completely by oxidisation.
In order for corrosion to take place, the metal needs to be exposed to either oxygen or water. If you can eliminate these, then you can help to prevent oxidisation and, therefore, corrosion from taking place. This could mean placing the metal in an airtight or water-tight container, which in some circumstances may be completely impractical. You can also use paint to cover the surface of the metal, but this will need to be reapplied, and it can be difficult to repaint a pipe when the existing paint starts to flake away in small pieces. This is where the surface coatings mentioned above come in useful, as they provide the protection that is needed in an easy and cost-effective way.