Application of the hottest zinc chromium coating o

2022-08-16
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The application of zinc chromium coating on military products (Part 1)

[Abstract] this paper introduces the characteristics and development status of zinc chromium coating, objectively evaluates the zinc chromium coating through many process tests, such as salt spray test, paper packaging shopping bag humidity test, mechanical property tensile test, and discusses the feasibility of applying zinc chromium coating to military products instead of zinc and cadmium plating

[Key words] military products; Galvanized; Zinc chromium coating

preface

zinc chromium coating technology is an inorganic anti-corrosion coating with flake zinc and zinc chromate as the main components, which is formed by dipping, spraying or brushing water-based zinc chromium coating on the surface of steel parts or components and baking at about 300 ℃. Compared with the traditional electro galvanizing and cadmium plating processes, the film has the characteristics of no hydrogen embrittlement, good corrosion resistance, strong adhesion to paint, good weldability, strong permeability, closed processing of small parts, and no environmental pollution. Due to the above advantages, especially the resistance to salt spray, heat resistance, humidity and heat, and a certain 12- resistance, it is better than processes such as electro galvanization, cadmium plating, hot galvanization, etc., so it is more suitable for products under humid tropical marine climate and industrial atmospheric conditions [

Dacromet technology entered China in the 1990s. At present, more than ten domestic units have introduced Dacromet production lines, but they are mainly used in the production of civil products. In order to apply this technology to military products as soon as possible and improve the surface coating quality of military products. Through the process test, the feasibility of Dacromet technology partially replacing the galvanizing process is discussed, which provides a scientific basis for the early application of Dacromet technology in military products

1 test

the test material is Q235 steel, and the specification of the test piece is 150mm × 70mm × 2mm Dacromet slurry is SDA type, and shot blasting is selected φ 0、3mm × Steel shot. Dacromet process is as follows: degreasing → shot blasting → dip coating, liquid throwing or spraying → baking and curing → cooling, secondary dip coating, liquid throwing or spraying → baking and curing → cooling → inspection → packaging → warehousing and transportation. For small parts such as screws, nuts, spring foam bodies and stamping parts, the dip coating and liquid throwing method can be used, while for some parts with large external dimensions that cannot be dip coated, the spraying method can be used to ensure that the thickness of the coating peek is uniform except for concentrated sulfuric acid. All specimens treated with Dacromet are treated with two coating and two baking processes

2 test results

2, 1 salt spray test

since fasteners are purchased standard parts, the neutral salt spray test is carried out simultaneously with the purchased galvanized standard parts in stock and the Dacromet standard parts treated by two coats and two ovens during the salt spray test. Refer to gb/t and gb/t standards

the test conditions are: the temperature in the salt spray test chamber is 35 ± 2 ℃, the concentration is 5%, and the pH value is 6,2. It can be seen from table 1 that the corrosion resistance of Dacromet coating is better than that of zinc coating

2, 2 humidity resistance test

refer to GJB 150, standard. Test for 10 cycles at a temperature of 35 ± 2 ℃ and a relative humidity of more than 95%, and observe the surface condition of the sample. It can be seen from table 2 that the moisture resistance of Dacromet coating is better than that of zinc coating

make the production process more efficient

(to be continued)

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