Phosphating and dross removal steps in the pretreatment process

• Previous
• Next

In the process of metal surface treatment, phosphating is an important pretreatment technology. Phosphating not only improves the corrosion resistance of the metal surface, but also enhances the adhesion of the coating to the substrate.

In order to ensure the smooth running of the phosphating process, slag removal is also an essential step. This article will detail the role of phosphating and slagging specific steps to help companies better understand and master this technology.

First, the role of phosphating

1. Improve anti-corrosion properties:

Phosphating treatment can form a layer of dense phosphate protective film on the metal surface. This protective film can effectively isolate the metal from contact with the external environment, thereby improving the corrosion resistance of the metal and prolonging the service life of the product.

2. Enhance the adhesion of the coating:

The microstructure of the phosphate film is porous, and this structure can enhance the mechanical bite of the coating and the metal substrate, improve the adhesion of the coating, and prevent the coating from peeling and blistering.

3. Improvement of coating performance:

The metal surface after phosphating treatment is more uniform, which can improve the leveling and adhesion of the coating in the coating process, thus improving the coating quality.

4. Prevent metal surface rust:

During storage and transportation, the phosphating film can prevent the metal surface from coming into contact with moisture and oxygen, reducing the risk of rust.

Second, the process of phosphating

1. degreasing and cleaning:

Before the phosphating process, the metal surface first needs to be degreased and cleaned to remove grease, dirt and other impurities from the surface. A clean surface helps the formation and uniform distribution of the phosphating film.

2. Acid washing to remove rust:

After degreasing and cleaning, the metal surface is acid washed to remove the rust layer and oxide skin on the surface. Acid washing can improve the activity of the metal surface and promote the phosphating reaction.

3. Neutralization by water washing:

After pickling, the metal surface needs to be washed and neutralized to remove the acidic residue on the surface, to prevent it from adversely affecting the formation of the phosphating film.

4. phosphating treatment:

The metal workpiece is immersed in the phosphating solution, and the phosphate in the phosphating solution reacts with the metal surface to form a dense phosphate film. The time and temperature of phosphating treatment are controlled according to different process requirements.

5. water washing passivation:

After the phosphating treatment, the metal surface is washed to remove the residues of the phosphating solution, and then passivated to further improve the corrosion resistance of the phosphating film.

Third, the steps of phosphating slag removal

Phosphating treatment process will produce a certain amount of dross. These dregs, if not removed in time, will affect the quality and uniformity of the phosphating film. Therefore, dross removal is an important step in the phosphating process. The following are the specific steps of dross removal:

1. Filtering and dross removal:

Installation of filtration devices in the phosphating solution circulation system, through physical filtration methods, to remove suspended particles and dross in the phosphating solution.

2. Regular slag discharge:

Regularly discharge the dross at the bottom of the phosphating tank to prevent the accumulation of dross from affecting the quality of the phosphating solution.

3. Replacement of phosphating solution:

According to the production situation and the service life of the phosphating solution, replace the phosphating solution regularly to maintain the activity and stability of the phosphating solution.

4. online monitoring:

Through online monitoring equipment, real-time monitoring of the composition and dross content of the phosphating solution, timely adjustment of process parameters to ensure the quality and stability of phosphating treatment.

Conclusion

Phosphating treatment is an indispensable step in the pretreatment of metal surface, which plays an important role in improving the corrosion resistance of metal, enhancing the adhesion of coating and improving the coating performance. To ensure the effect of phosphating treatment, dross removal is an essential step. Through effective dross removal measures, the cleanliness and activity of the phosphating solution can be maintained to ensure the quality and uniformity of the phosphating film, thus improving the overall quality and performance of the product.