In order to add better rust protection steel is often put through a process called Galvanizing. The galvanizing process involves the coating of the steel with zinc. Zinc is used because of its superior corrosion resistance over steel or iron.  The metallurgical properties of a zinc coating protects better than painting because the zinc continues to protect the steel even is small sections, scratches, of the steel are exposed to the air.  This is a significant advantage over painting. Galvanizing is a relatively low cost process which still allows for the cold working, bending, of sheet metal.

Hot Dipped Galvanized Steel

There is only one way to galvanize steel, by use of a galvanic cell, however hot dip zinc coated steel is often referred to as galvanized because of their similar qualities.  The two methods achieve the same thing, a coating of zinc chemically bonded to the steel; however the methods, thicknesses and finished looks are different.  Most significant to sheet metal work is understanding how the thickness is changed.  Electroplating produces a thinner coating compared to hot dipping which makes it less suitable for outdoor use. Visually the electroplating method will produce a shiner coating similar to that of stainless steel while the hot dipping method will produce a matte grey coating. Electroplated steel is also cheaper than hot dipping which can be advantageous if your application allows it. Be sure to check with your steel supplier as to how your sheets are coated.

Galvanized Coating Thicknesses

As you can see from our first chart the galvanized columns are thicker than the regular steel.  The process of galvanizing bonds a layer of zinc to the steel.  This layer’s thickness can be controlled and the different thicknesses are designated below.  The thicknesses are based off of how many ounces per square foot of the galvanizing material is added to the base steel.

 Triple SpotSingle Spot
DesignationBoth SidesOne SideBoth Sides
G60 / A60.60.20.50
G40 / A40.40.12.30
G30 / A30.30.10.25