Improve the corrosion resistance of phosphating fasteners

Improve the corrosion resistance of phosphating fasteners. After comparing various phosphating solutions, PF-MIAM and PF-MIAR phosphating solutions are used. The composition and ratio of the solution have a great influence on the quality of phosphating. When the self-adjusting calcium salt phosphating solution is used for production, the phosphating film formed on the surface of the workpiece has coarse crystals, more ash, and poor product appearance quality. The prepared black phosphating solution produces relatively more precipitation during the production, and it is basically necessary to dredge the waterlogged sediment every day.

Too high total acid will make the film too thin, and too low total acid will make the film loose and rough. The acid ratio refers to the relationship between free acidity (Tb) and total acidity (Ta). If the free acid is too high, it will react quickly with steel parts, and will cause a large amount of hydrogen to evolve, making the interface layer phosphate difficult to saturate, resulting in difficulty in the formation of crystal nuclei, coarse crystals in the film, loose and porous, reduced corrosion performance, and phosphating time Prolonged; the free acid is too low, the phosphating film is thin, and even no phosphate film is formed. (Guide: Four reasons why screws and bolts often break)

The main component of the solution is low: add the main solution. Incorrect acid ratio: The free acidity is too high, and manganese carbonate can be added to adjust: the total acid is too low, and the main agent can be added to adjust, and the total acid should be controlled above 85. Poor solution composition ratio: Improve the phosphating solution formula and use PL-VM phosphating solution.

Use PL-VM phosphating solution, the solution parameters are easy to adjust, there is less sediment, the workpiece is dusted, the film layer is finely crystallized, and the neutral salt spray resistance time can be improved, and the workpiece will be corroded after the neutral salt spray test The degree is small.

The composition of the self-prepared phosphating solution is not well controlled, the solution adjustment is difficult, the precipitation is much, the workpiece is hung in the dust, and the workpiece is easy to cause over corrosion during the phosphating process.

More related hardware stamping parts industry news: