In some passivation solution formulas, acids such as nitric acid, sulfuric acid, phosphoric acid, and acetic acid are added. The advantages of doing so are as follows: it promotes the dissolution of chromates, accelerates the formation of the passivation film and the dissolution of zinc, stimulates the generation of hydrogen, speeds up the formation of the passivation film, and results in a passivation film with good gloss.
However, there are also disadvantages: it reduces the effective thickness of the pure zinc layer, roughens the surface galvanized layer, and may cause yellow and red spots to appear. Furthermore, the addition of acids is also unfavorable for waste treatment.
