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What processing needs to be done on the hardware pre-treatment production line?
- 2020-03-03-

1.Degreasing and rust removal

A good-quality phosphating film is only formed on the surface of the workpiece that has completely removed foreign matters such as oil, rust, and scale. Oil stains, rust, and scale remaining on the surface of the workpiece will severely prevent the growth of the phosphate film. In addition, it also affects the coating's adhesion, drying function, decoration function and corrosion resistance function. The complete removal of these foreign matters is a necessary condition for phosphating.

2.washing

Although water washing after degreasing and rust removal is an auxiliary process before painting, it also needs to be given sufficient attention. After degreasing and rust removal, some non-ionic surface active agents and CL- etc. are easily attached to the surface of the workpiece.

If these residual materials are not completely cleaned, it may cause the phosphating film to become thin, linear defects may occur, and even phosphorization may not be achieved. Therefore, to improve the quality of water washing after degreasing and rust removal, multiple rinses, two water rinses, 1-2min at all times, and frequent replacement of clean water are required to ensure that the pH value of clean water is between 5-7.

3.Phosphating

The so-called phosphating refers to a method in which a metal workpiece is treated with an acidic solution containing a dihydrogen phosphate and a chemical reaction occurs to form a stable insoluble phosphate film on the surface. The resulting film is called a phosphating film. The primary purpose of the phosphate film is to increase the adhesion of the coating film and improve the corrosion resistance of the coating.

There are many methods of phosphating. According to the temperature of phosphating, it can be divided into high temperature phosphating (90-98 ℃), medium temperature phosphating (60-75 ℃), low temperature phosphating (35-55 ℃) and Phosphating at room temperature.

4.Passivation

The passivation skills of phosphating film are widely used in North America and European countries. The use of passivation skills is based on the characteristics of the phosphating film itself. The thickness of the phosphating film is thin, generally 1-4g / m2, and the zui does not exceed 10g. / m2, its free pore area is large, and the corrosion resistance of the film itself is limited.

Some even quickly develop yellow rust during the drying process. After passivation, a passivation shutdown process can be performed, so the exposed metal in the pores of the phosphating film can be further oxidized, or a passivation layer can be formed, which can fill the phosphating film. The oxidation effect makes the phosphating film stable in the atmosphere.

5.Drying of phosphating film

Drying the phosphating film can have two effects. On the one hand, it prepares for the next process of painting to remove the moisture on the outside of the phosphating film. Corrosion resistance.

To set up a hardware pre-treatment production line, the process design must be completed before designing, manufacturing and installing non-standard equipment. Therefore, process design is the basis for establishing a production line, and correct and reasonable roads will have a good impact on production operations and product quality.