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Anticorrosive process of fasteners

Oxidation is also called blackening or bluing. The workpiece is heated in a solution of air, water vapor or chemicals at room temperature or an appropriate temperature to form a blue or black oxide film on the surface of the workpiece to improve its corrosion resistance and appearance. Surface treatment process.

In machinery manufacturing, NaOH solution heating is commonly used to blacken the workpiece. Compared with galvanizing and chrome plating, the cost is lower and the effect is good.

The black oxide film formed by blackening has a thickness of 0.5-1.5 μm and has a lower corrosion resistance than other chemical films.


Zinc (aluminum) chromium coating is also called Dacromet, Daque Rust, Dickron. It is also called zinc-chromium coating in China. It is a new type of anticorrosive coating with zinc powder, aluminum powder, chromic acid and deionized water as the main ingredients.

The process of formulating Dacromet treatment solution into a water-soluble coating, and then directly coating it on a clean workpiece surface, and baking and curing to form a Dacromet coating.

Dacromet coating process

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Dacromet is a new type of surface treatment technology. Compared with the traditional electroplating process, Dacromet is a "green plating". Its advantages are as follows:

1) .Super corrosion resistance: Dacromet film thickness is only 4-8μm, but its rust-proof effect is more than 7-10 times than traditional galvanizing, hot-dip galvanizing or coating method. The standard parts and pipe fittings processed by Dacromet process did not show red rust for more than 1200 hours after the salt spray test.

2). Hydrogen-free embrittlement: Dacromet's treatment process determines that Dacromet does not have hydrogen embrittlement, so Dacromet is very suitable for coating of stressed parts.

3). High heat resistance: Dacromet can withstand high temperature corrosion, and the heat resistance can reach above 300 ℃. In the traditional galvanizing process, the skin is scrapped when the temperature reaches 100 ° C.

4). Good adhesion and recoating performance: Dacromet coating has good adhesion to the metal substrate, and has strong adhesion to other additional coatings. The treated parts are easy to spray and color, and are compatible with organic coatings. The binding force even exceeds the phosphating film.

5). Good permeability: Due to the electrostatic shielding effect, it is difficult to galvanize the deep holes, slits of the workpiece, and the inner wall of the pipe, so the above parts of the workpiece cannot be protected by electroplating. Dacromet can enter these parts of the workpiece to form a Dacromet coating.

6). Non-pollution and pollution: Dacromet will not produce waste gas that pollutes the environment during the entire process of production and processing and coating of workpieces, and no waste treatment is needed, reducing the cost of treatment.