| 摘要 |
<p><PICT:1118476/C6-C7/1> A zinc phosphate coating is formed on iron and steel by treating the metal with an aqueous acidic fluoride free zinc phosphate solution containing one or more oxidizing agents such as nitrates, nitrites, chlorates and bromates and at least 0.5 g/l boric acid calculated as H3BO3, the total P2O5 content being 2-12 g/l and the weight ratio of free P2O5 to total P2O5 lying within the area ABCD on the graph shown in the drawing. The solution may contain 1.5-4g/l H3BO3 as H3BO3, Na2 B4 O7 or as NaBO2, at least 3 mgm/l of a titanium phosphate activator, up to 4g/l tartaric acid and 0.05 - 1g/l of a non ionic surface active agent such as ethexylated alkyl phonols and straight chain fatty alcohols. The tartaric acid may be added as such or as a soluble salt such as Rochelle salt. The pH of the solution is 2 - 3.5 and the ratio of free to total P2 O5 is adjusted by altering the pH by adding NaOH. The phosphated metal may be rinsed with water and then with a solution containing CrO3.</p> |
