Hot dip galvanized and cold galvanized difference is as follows:
1, hot dip galvanized as metal anti-corrosion way, it will usually be around 500 ℃ derusting processing steel structure in liquid zinc, zinc layer on the surface of steel structure. Cold galvanizing is through electrolysis adhered on the surface of the metal material such as a layer of metal film, make the material surface texture is uniform and anticorrosive wear-resisting, external appearance more beautiful.
2, hot dip galvanized coating thicker, generally for 30 to 60 micrometers, coating anticorrosion ability is higher. Suitable for outdoor work steel parts, such as highway fence, power tower, large-sized fasteners are "rough" long-term rust artifacts. Cold galvanizing, surface smooth level off, but because of the coating is thin, generally within 5-30 microns, so the corrosion time is short. Are used in indoor use the rust parts, such as the bottom of the chassis, panels, small specification fasteners, etc.
3, hot dipped galvanized by the principle of atmospheric corrosion resistant zinc, electrochemical protection, the material such as iron and steel for zinc carbonate on the surface of the protective film can reduce the speed of the zinc corrosion, even if broken, will form of zinc film layer again. Cold galvanizing is to use chemical ways, separating the zinc alloy into zinc ions, has attached on the steel surface, this way to form new layer is thinner, the iron and steel in the general case, prone to rust.
4, cold galvanized surface is smooth, bright, colorful passivation technology of galvanized coating can present yellowish green, white passivation technology of plating can present bluish white, usually only a small amount of zinc layer on both ends of the steel tube of cold galvanization, there is no galvanized layer in the farther. Galvanized surface is rough, the color is darker, general is silvery white, because production occurs on the surface of 1 order in some water lines and tumor, surface is not shine, nor reflection. Hot dip galvanized steel pipe internal and external are complete galvanized layer.