Coating iron and steel

Paints are commonly used to exclude oxygen and water, and thus protect the surface of iron and steel. It is important that the coating is continuous, as even pinholes allow the formation of corrosion cells in which an anodic area develops under the film around the hole, causing corrosion to spread.

If a sacrificial coating such as zinc or aluminium is applied, the polarity is reversed and the coating sacrificially protects the ferrous metal.

Nobler metals, such as chromium, tin, copper and their alloys, are often used as protective or decorative coatings for ‘indoor’ metalwork, but in fact offer no electrolytic protection.

Updated: 3 сентября, 2015 — 8:02 пп