How to prepare zinc phosphating solution for steel surface phosphating?

The main components of phosphating solution are dihydrogen phosphate, such as Zn(H2PO4)2, and a proper amount of free phosphoric acid and accelerant. The accelerator mainly plays the role of reducing phosphating temperature and accelerating phosphating speed. As chemical accelerators, the most commonly used oxidants are NO3-, NO2-, clo 3-, H2O2, etc. Phosphating is a process in which metals react with dilute phosphoric acid or acid phosphate to form phosphate protective film. Phosphating solutions are mainly divided into six categories according to the phosphating film-forming system: zinc series, zinc-calcium series, zinc-manganese series, manganese series, iron series and amorphous iron series.

The main components of zinc phosphating bath solution are: Zn2+, H2PO3-, NO3-, H3PO4, accelerant, etc. The main components of phosphating film (steel parts) are Zn3 (PO4) 2 4h2o and Zn2fe (PO4) 2 4h2o ... The phosphating grains are dendritic, needle-like and porous. Widely used in priming before painting, anti-corrosion and antifriction lubrication in cold working. According to phosphating temperature, it can be divided into four categories: normal temperature, low temperature, medium temperature and high temperature. Normal temperature phosphating is unheated phosphating. The general treatment temperature of low-temperature phosphating is 30 ~ 45℃. Medium temperature phosphating is generally 60 ~ 70℃. High temperature phosphating is generally greater than 80℃. The temperature division method itself is not strict, and sometimes there are sub-moderate temperature and sub-high temperature methods, depending on your wishes, but generally follow the above division method.

Formula of zinc phosphating solution (for reference only):

Component feed (g/L)

96-98 parts of zinc dihydrogen phosphate

Ammonium molybdate 7-8

8-9 parts of magnesium sulfate

25-26 parts of calcium nitrate

Hydrofluoric acid 1~2

9~ 10 phosphoric acid

Nitric acid 12~ 13

6.5-7 parts of nickel nitrate

2.5-3 parts of sodium nitrite

Tartaric acid 5-5.5

Water surplus