Hot-dip galvanizing (HDG) is used to protect steel from corrosion in a variety of environments, including air, water, chemicals, and soil applications. Galvanized steel’s performance in each of these applications is dependent upon a unique set of corrosion variables. The information in the subsequent pages details what variables impact the coating’s performance and how long it will last in the given environment. To learn more, view the Specifier’s Guide.
Most commonly, hot-dip galvanized steel applications are in the atmosphere or open air. In atmospheric applications, hot-dip galvanized steel naturally exposed to wet and dry cycles which are crucial to the development of a series of films on the zinc surface known as the patina. The patina is stable and non-reactive unless exposed to aggressive chlorides or sulfides, and is a key component to galvanizing’s long life. A number of independent and industry tests of galvanized steel samples have been performed over decades in industrial, urban, rural, and marine environments to determine the time to first maintenance in each environment. It is important to note the data represented on this site about galvanized steel’s performance is based on actual performance in the field, and not on accelerated testing methods. Manufacturers of many other corrosion protection systems use these tests to claim their products perform as well as hot-dip galvanized steel based on accelerated testing, namely salt spray tests. However, salt spray tests do not allow the zinc coating to go through the natural wet and dry cycles required to form the zinc patina.