Hot Dip Galvanizing, pre-galvanizing and electro-galvanizing compared
The process where steel is coated with protective corrosion resistant zinc is known as galvanization. The coating formed by the zinc protects the steel from corrosion and in cases where the coating gets scratched, the steel is still protected. Please note that galvanizing does not change the mechanical properties of the steel.
For industries or environments where steel needs to be protected from corrosion without using stainless steel, galvanized steel or painted steel can be used. There are three common methods of galvanization which include: hot-dip galvanizing, pre-galvanizing and electro-galvanizing. The choice in method will depend on the application of the end product as well as the environments it will be applied.
Hot Dip Galvanized Steel
Hot dip galvanizing process is where an already formed part, for example a plate, round, square or rectangular tube is dipped in bath containing zinc. A reaction takes place between the steel and the zinc during the time the part is in the zinc bath. The thickness of the zinc coating is influenced by a number of factors, including the surface of the steel, the time the steel is dipped in the bath, the composition of the steel as well as the steel's size and thickness.
One advantage of hot dip galvanizing is that the entire part is covered including edges, welds, etc. giving it an all-round corrosion protection. The end product can be used outdoors in all different weather conditions. It is the most popular galvanizing method and is widely used in the construction industry.
Pre-galvanized steel refers to steel which was galvanized while it is in sheet format, thus prior to further manufacturing. Pre-galvanization is also known as mill galvanized as the steel sheet is rolled through molten zinc. After the sheet is sent through the mill to be galvanized it is cut to size and recoiled. A specific thickness is applied to the entire sheet, for example pre-galvanized Z275 steel has a 275g/m2 zinc coating. One of the advantages which pre-galvanized steel has over hot dip galvanized steel is that it has a better appearance.
Pre-galvanized materials are used for a wide variety of products including conduit, lip and open channels.
Electro Galvanized Steel
Electro galvanized steel refers to applying a zinc coat deposited onto the steel using electrodeposition. Electro galvanized steel has the advantage that the coating thickness can be controlled independently on the in- and outside parts. The thickness of the coating applied through electro galvanization is very accurate.