Key points of phosphating process for the hottest

2022-07-31
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Key points of phosphating process for automotive fasteners

automotive fasteners are often protected against rust by galvanizing or phosphating. Relatively speaking, the former has good protection, cr6+ will cause cancer during passivation, and will also cause hydrogen embrittlement of the workpiece, so it is necessary to drive hydrogen after plating; The latter basically does not change the mechanical properties and geometric dimensions of the workpiece, the film thickness can be increased according to the requirements, and the protection can be improved if it needs to be immersed in antirust oil, which can meet the requirements of mass production of automotive fasteners. The key points of the process are as follows:

1 pretreatment

1.1 degreasing: after heat treatment or machining, the fastener surface is stained with a lot of oil, and the degreasing agent is used in the plastic tank

1.2 rust removal: shot blasting, sand blasting, etc. can be used to remove serious oxide skin on the fastener surface. The speed of removing oxide skin is fast and the sand blasting surface is uniform, but removing oxide skin is the key link

for low strength ≥ 8.8 grade, concentrated hydrochloric acid can be used (the smoking effect is better). Advantages: strong chemical solubility in metal oxides 3 Equipped with a wide screen LCD control system, the protection requirements of the product itself are relatively good. Its derusting ability is almost proportional to the concentration. When the concentration and temperature are the same, the etching speed of hydrochloric acid is 1.5 ~ 2.0 times faster than that of sulfuric acid. After etching, there are less residues on the fastener surface, and the acid pickling surface is gray and smooth, which is convenient for phosphating

2 surface adjustment

surface adjustment is an indispensable process of zinc series. The current surface adjustment process can further improve the quality of phosphating film (dense and fine film, good rust resistance), which is particularly important for the "phosphorous" of automotive fasteners

3 soaking in oil

soaking in oil after saponification of the phosphating film can improve the ability of the phosphating film to resist neutral salt spray (for example, when the phosphating film weighs 16g/m2, the soaking in oil can withstand medium temperature salt spray for 550h)

the antirust performance of the traditional base oil soaked in heat (such as mechanical oil, spindle oil or transformer oil at 105 ~ 110 ℃ for 5 ~ 10min) is very poor. Only adding antirust agent can improve the antirust performance of the base oil. The greatest advantages of antirust oil are its resistance to salt water, salt mist, humidity, acid neutralization and good water replacement performance. Good dehydrated antirust oil can be prepared by adding antirust agent to base oil

4 shake dry

fasteners soaked in antirust oil can be shaken dry by stirring to avoid too much oil. (end)

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