Surface treatment, the silicon steel sheet phosphating film is always uneven, corrosion resistance is not good. But the iron will be fine
The content of manganese ion increases the hardness and adhesion of phosphating film, and improves the corrosion resistance. When the zinc ion content is high, the phosphating speed can be accelerated, and the phosphating film is compact, and the grain grain is full and phosphorescent. When the zinc ion content is low, the phosphating film is loose and dark. General zinc and manganese ions should be kept within the range of 1.5 ~ 2:1.
The ratio of free phosphoric acid to total acidity is very important in phosphating process. When the free phosphoric acid for a long time, the hydrolysis reaction in reverse, resulting in reduced phosphate hydrolysis of phosphating solution and phosphating time long, coarse crystallization and precipitation increased, when the free acidity is low, hydrolysis reaction positive, produced acid phosphate, the film quickly and the nucleation, the phosphate film, if free acidity too low can not form phosphating film. Therefore, phosphating should pay attention to the ratio of free acidity and total acidity, and generally control between 1:9 and 11.
From your phosphating temperature see, your craft belongs to medium temperature phosphating, medium temperature phosphating at 50~70 degrees Celsius temperature phosphating. The advantage of medium temperature phosphating is that the free acidity is stable, easy to master, phosphating time is short, production efficiency is high, and phosphating film has high corrosion resistance. The grain size and corrosion resistance of phosphating film depend on the composition of phosphating solution. Manganese phosphate salts, two hydrogen phosphate zinc and zinc nitrate ratio properly, Mn +: Zn2 ten 1:1.5 is the best, the phosphating film formed relatively uniform and compact.
