METHOD OF ZINC PHOSPHATING WITH INTERNATED ADDITIONAL PASSIVATION Russian patent published in 2002 - IPC

FIELD: phosphating of surfaces of metals with acid solutions. SUBSTANCE: method of phosphating metallic surfaces from steel, from zinc plated steel or from steel coated with zinc alloys, from aluminium and/or aluminium-magnesium alloys comprises metal surfaces with zinc-containing phosphating solution for period of 3 sec to 8 min when sprayed with solution or immersed into solution containing from 0.2 to 3g/l of zinc ions, from 3 to 50 g/l of phosphate ions calculated for PO₄ from 0.001 to 4 g/l of manganese ions, from 0.001 to 0.5 g/l of one or more polymers selected from polycarboxylates, polymeric phosphonic acids, polymeric phosphinocarboxylic acids, nitrogen-containing organic polymers and poly-4- vinylphenol compounds of general formula II: wherein n is integer from 5 to 100, X is independently hydrogen atoms or -CRR¹OH, wherein R and R¹ are hydrogen atom, aliphatic and/or aromatic residues having from 1 to 12 carbon atoms and one or several accelerators selected from m-nitrobenzoate ions with concentration of 0.05 to 2 g/l, n-nitrophenol with concentration of 0.005 to 2 g/l, hydroxyamine in free or bonded form with concentration of 0.1 to 10 g/l, reducing sugar with concentration of 0.1 to 10 g/l, phosphating solution containing not higher than 0.5 g/l of nitrate, and ratio of amounts of phosphate ions to amount of zinc ions varying from 3.7 to 30. Method makes it possible to improve corrosion resistance and increase strength of coatings and make corrosion resistance greater. EFFECT: more efficient phosphating method. 16 cl, 1 tbl