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Saturday, July 31, 2010

Cold Galvanizing or Hot Dip Galvanizing

What is cold galvanizing and why is it not hot dip galvanizing?

Cold galvanizing is another form of a barrier coating on iron or steel. No doubt it is a good form of corrosion protection for steel as it is another type of paint with some zinc dust additive. The paint which may be either epoxy or alkyd, acts as a barrier coat whilst the zinc dust gives the additional galvanic sacrificial property to this type of paint. The advantage of this type of zinc rich paint is it can be stored in drums or aerosal spray cans. It is easy to carry around and can be used to repair bare iron or steel surface. For best results the iron or steel surface has to be properly cleaned and application has to be at low humidity.

Cold Galvanizing paints will not produce a coating similar to the hot dip galvanizing coating. Cold galvanizing can not replace hot dip galvanizing as hot dip galvanizing has to be performed in a specially build plant with huge chemical tanks, heavy lifting cranes and a huge zinc bath filled with molten zinc at 450 degree Celsius. When iron of steel are hot dip galvanized the surface of steel is transformed to a series of iron zinc alloy layers. This coating is metallurgical bonded to the base steel. These series of alloy layers are actually harder than the base steel and it is a galvanic sacrificial zinc layer on steel.