Galvanizing

Galvanizing, process of coating a base metal, such as iron or steel, with a thin layer of zinc to protect the base metal from corrosion. Zinc is applied with greater ease and at lower cost than other metallic coatings such as tin, chromium, nickel, or aluminum. The zinc layer protects the base metal even when there are cracks or small gaps in the coating, because oxygen reacts more readily with zinc than with the exposed base metal.

The most widely used method of galvanizing is the hot dip process. The iron or other base metal is pickled (immersed in acid) to remove dust, dirt, and grease. It is then washed and dipped into the spelter, that is, molten zinc. In a different galvanizing process known as sherardizing, the article to be galvanized is covered with zinc dust and heated in a tightly closed drum for several hours at 300° to 420° C (572° to 788° F). Other methods of galvanizing include depositing the zinc electrolytically (see Electrochemistry) and applying molten zinc in the form of a fine spray. Some examples of commonly galvanized products are garbage cans, corrugated sheets for roofing, iron pipe, and fencing wire.