For phosphating solution,  ZnO 99.7% is generally produced by indirect method.   Zinc oxide mainly provides zinc ion in phosphating solution  , which is the main component of phosphating film. Zinc oxide is reacted to obtain zinc phosphate,  which can be used for anticorrosion and rust prevention on  metal surfaces ,  that is  , zinc-coating is formed on the metal surface as an anti-rust pigment. 

The reaction formula of the whole phosphating solution:

Phosphoric acid + zinc oxide → zinc dihydrogen phosphate +  water

+ zinc oxide → + water

The concentration of zinc dihydrogen phosphate in production must be effectively  controlled  to achieve the goal.

First, the quality indicators