| 摘要 |
<p>A method of forming a chemical phosphate coating on the surface of steel with a treatment bath made without directly adding any oxidizing agent such as nitrite ions or hydrogen peroxide, and maintaining its temperature in a range not exceeding 40°C, its pH in the range of 2.5 to 4.5 and its oxidation-reduction potential (ORP in terms of the normal hydrogen electrode potential) in the range of 150 to 550 mV. The bath is formed from an aqueous solution of the two components, i.e. the first component, an acidic solution consisting mainly of oxo acid ions, such as NO3, phosphoric ions (H3PO4 or H2PO4- ), and metal ions, such as Zn2-, and the second component, an alkaline solution containing hydroxide ions (OH- ). Preferably, the bath has a temperature of 20°C to 30°C, a pH value of 3.0 to 4.0 and an ORP of 350 to 450 mV.</p> |
