Galvanized iron is iron which has been coated in a layer of zinc to help the metal resist corrosion. Steel can also be galvanized. When metal is going to be used in an environment where corrosion is likely, it is often galvanized so that it will be able to withstand the conditions. Even with galvanization, however, corrosion will eventually start to occur, especially if conditions are acidic.
There are two primary techniques which can be used to make galvanized iron. The most common is hot-dip galvanization, in which the iron is moved through an extremely hot bath of molten zinc, which may be mixed with small amounts of lead, depending on the circumstances. When the iron emerges from the bath, the zinc will have bonded, creating a layer of zinc on the surface of the iron. Sometimes, the metal may be passed through a mill to flatten and even out the coating. Another technique which can be used is electrodeposition, also known as electroplating, although this is rare.
Once galvanized, iron is covered in a layer of zinc which may be shiny to dull gray. The zinc can be painted, if desired, or left plain. Painting is often done when the iron must match other building materials, or when people want to make it less obvious. In the garden, for example, it may be painted green so that it will blend in with foliage instead of standing out.
As long as the zinc coating remains intact, the galvanized iron should remain in relatively good condition. However, acidic conditions can erode the zinc over time, creating patches where corrosion can occur. Corrosion can also occur when the coating is penetrated, as when someone drives a nail through a sheet of galvanized iron, exposing the iron inside to the elements. Once corrosion starts, it can spread under the zinc, eventually causing the metal to fail.
There are a wide range of uses for this type of iron, which comes in pipes, stakes, sheeting, and wire, among other formats. Many hardware and home supplies carry galvanized iron products and may be willing to cut pieces to custom sizes by request. People can also be referred to professionals who will weld or cut galvanized iron to meet the needs of a particular project.
By Mary McMahon
Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a About Mechanics researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.