1, the principle:Since zinc is not easy to change in dry air, and in the humid air, the surface can generate a very dense zinc carbonate film, this film can not effectively protect the internal corrosion. And when the damage occurs for some reason the coating is exposed when the substrate is not too large, zinc and steel substrate forming micro-battery, the fastener substrate becomes cathode protected. In the automotive and transportation industries in the wider application, but the need is trivalent chromium passivation layer, a zinc-nickel alloy plating sealer coat, reducing hexavalent chromium passivation harmful, toxic layer.
2 Features:Thick zinc coating, fine crystalline, homogeneous and non-porous, good corrosion resistance; the resulting layer of pure zinc plating, acid, alkali and other corrosive mist slow sand Eng protect fastening member base, galvanized by the chromium layer after the formation of acid passivation white, color, army green, etc., nice, with some decorative, since zinc coating has good ductility, it can be cold-rolling, bending and other forming without damage coating.
3, the scope of application:Galvanized field covered more widely applied throughout the fastener product machinery manufacturing, production of galvanized chain link fence, electronics, precision instruments, chemicals, transportation, aerospace, which are of great significance in the national economy.
1, the principle:Hot-dip zinc coating is zinc in the liquid state, three-step formation of the iron-based surface is liquid zinc dissolved to form a zinc-iron alloy phase layer; alloy layer of zinc ions further into the base diffusion form a zinc, iron miscible layer; an alloy layer wrapped surface layer of zinc.
2 Features:Pure zinc layer has a thick dense cover on the surface of steel fasteners, which avoids any contact with the steel substrate etching solution, protecting the substrate from corrosion steel fasteners. In the general atmosphere, the zinc layer surface to form a thin and dense layer of zinc oxide surface. It is difficult to dissolve in water, so the substrate steel fasteners play a protective role. If zinc oxide and other ingredients in the atmosphere to form insoluble zinc salts, the corrosion effect is more ideal; with zinc – iron alloy alloy layer, combined with the dense, performance-specific corrosion resistance in marine and industrial atmosphere, salt spray atmosphere; due to the combination firm, zinc – iron solubility, with strong wear resistance; Because zinc has good ductility, the alloy layer and steel substrate attached to a solid, and therefore can be galvanized cold-rolling, drawing, bending and other molding process, do not damage the coating; steel structure after hot-dip zinc, equivalent to a annealing treatment can effectively improve the mechanical properties of the steel substrate, eliminating stress molding steel welding, steel structures conducive to turning; heat dip zinc surface fastener after the bright and beautiful; pure zinc layer is a hot-dip zinc richest layer of galvanized plastic layer, which is close to the basic nature of pure zinc, has good ductility.
3, the scope of application:This plating method is particularly suitable for highly corrosive environment of various acid, alkali mist like.