Types of Galvanizing(Zinc Plating)

Galvanizing refers to a surface treatment technique that involves coating a layer of zinc on the surface of a metal, alloy, or other material for aesthetic and rust prevention purposes. The main methods used are hot-dip galvanizing, electrogalvanizing, and mechanical galvanizing.

Author:Marisa

01 Cold galvanizing=Electro Galganizing=Zinc Electroplating

Cold galvanizing, also known as electrogalvanizing, is the process of using electrolytic equipment to process and then galvanize pipes. After processing, the pipe fittings are placed in the solution and connected to the negative electrode of the electrolysis equipment. A zinc plate is placed opposite the pipe fittings and connected to the positive electrode of the electrolysis equipment to connect the power supply. By using the directional movement of current from the positive electrode to the negative electrode, a layer of zinc will be deposited on the pipe fittings.

The zinc coating is thick, with fine and uniform crystallization without pores, and good corrosion resistance; The zinc layer obtained from electroplating is relatively pure and corrodes slowly in acid, alkali and other mist, which can effectively protect the substrate of fasteners. The galvanized layer forms white, colored, military green, etc. after chromate passivation, which is beautiful and elegant, and has a certain degree of decoration. Due to the good ductility of the galvanized layer, it can be formed through various processes such as cold stamping, rolling, bending, etc. without damaging the coating. The fields involved in electroplating are becoming increasingly extensive, and the application of fastener products has been widely spread in mechanical manufacturing, the production of galvanized wire mesh, electronics, precision instruments, chemical engineering, transportation, aerospace, and other fields, which have significant applications in the national economy.

02 Mechanical galvanizing

In a rotating drum containing plated parts, glass balls, zinc powder, water, and accelerators, the glass balls used as the impact medium rotate with the drum, causing friction and hammering with the surface of the plated parts. Under the action of chemical accelerators, the coated zinc powder is "cold welded" to the surface of the plated parts, forming a smooth, uniform, and fine coating with a certain thickness.

03 Hot dip galvanizing

The main method used for surface galvanizing of steel plates is hot-dip galvanizing.

Hot dip galvanizing has a history of 170 years since France applied it to industry in 1836. In the past thirty years, with the rapid development of cold rolled strip steel, it has achieved large-scale development.

Hot dip galvanizing is the process of reacting molten metal with an iron substrate to form an alloy layer, thereby combining the substrate and coating. Hot dip galvanizing is the process of first pickling steel parts to remove iron oxide from the surface. After pickling, it is cleaned in a solution of ammonium chloride or zinc chloride, or a mixture of ammonium chloride and zinc chloride, and then sent to the hot-dip galvanizing tank. Hot dip galvanizing has advantages such as uniform coating, strong adhesion, and long service life.

The hot-dip zinc layer is formed by dividing zinc into three steps in liquid state, and the iron based surface is dissolved by the zinc liquid to form a zinc and iron alloy phase layer; The zinc ions in the alloy layer further diffuse into the matrix to form a zinc iron miscible layer; The surface of the alloy layer is wrapped with a zinc layer. This plating method is particularly suitable for various strong corrosive environments such as strong acid, alkali mist, etc.

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