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Galvanized characteristics
publishers£º¹ÜÀíÔ± Release time£º2012-5-5 9:30:06 read£º2413times
 

The appearance of the zinc coating was white, It is curved gender metal that standard electrode potential is -0.76V,soluble in acid and dissolved in alkali. Almost no change in zinc dry air, the corrosion of zinc in the critical humidity is greater than 70% in a humid atmosphere with carbon dioxide and oxygen effects generate a layer of basic zinc carbonate film, this film has a certain degree of relief eclipse the role of zinc and hydrogen sulfide and other sulfide-bearing reacts to generate zinc sulfide; zinc vulnerable to chloride ion etching, it is unstable in seawater. Zinc in confined or poorly ventilated, humid air conditions, contact with non-metallic materials, volatile compounds (low molecular weight carboxylic acids, aldehydes, phenols, ammonia, etc.), zinc vulnerable to corrosion, corrosion products to form a white loose, commonly known as hoarfrost ". Zinc in high-temperature, high humidity, confined conditions, the release of volatiles and bakelite, paint, wood contact, tend to the growth of filamentous single-crystal zinc, commonly known as "Long Hair". Zinc negative standard potential than iron, the iron and steel anode coating can provide a reliable electrochemical protection. In the industrial atmosphere rural atmosphere and iron and steel products used in the marine atmosphere can be selected zinc protective layer, the protective life relationship is almost proportional to the thickness of the zinc coating. Where the industrial air pollution in the atmosphere, the corrosion of the zinc coating is superior to cadmium plating, on the contrary in the sea or sea water. 

Zinc coating after by chromate passivation, corrosion resistance can be increased by 6 - 8 times. Therefore, passivation treatment is essential to the steps. Staining in the organic passivation film for low file protection --- decorative coating. In order to reduce the zinc coating thickness can improve the corrosion resistance at home and abroad to adopt the following two measures: First, to improve the quality of the passivation film, such as blue, green, army green, black passivation instead of the conventional rainbow color passive film , especially in military green passive film on the corrosion resistance of the best; by thin iron 0.3% - 0.6% Zn-Fe alloy, or nickel-containing 6% -10% of the Zn-Ni alloy instead of pure zinc coating, corrosion more than three times the performance, widely used in automotive steel instead of galvanized. Use of the zinc coating 
temperature not exceeding 2500C, tissue deformation at this temperature zinc crystalline, brittle, corrosion resistance decreased. Corrosion resistance, heat resistance requirements of the parts is preferable to the Zn-Ni alloy layer. 

Galvanized electrolyte can be divided into two major categories of alkaline and weakly acidic, at home and abroad commonly used with or without cyanide zincate zinc, cyanide zinc ammonium galvanized Chloride Zinc sulfate zinc. Domestically, non-cyanide zincate zinc is still the mainstream. In recent years, improvements to improve the performance of galvanized additives, chloride zinc plating and low cyanide bright galvanized rapid development of the ammonium salt galvanized continue to decline. Select bath according to the plated material, shape, appearance requirements, such as the stamping of small parts and complex parts, in particular, the auxiliary anode deep hole or tubular parts better to use the alkaline bath; sensitive to hydrogen embrittlement is preferable to weak acid zinc plating solution. When using two different performance of the bath, to produce very favorable.

 

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