Phosphate coatings for metal surfaces.

摘要

A process for phosphating a metal surface which comprises treating the metal surface with an acidic aqueous phosphate solution containing:- (a) from 0.1 to 2.0g/l of zinc ion; (b) from 5 to 40g/l of phosphate ion; (c) a phosphating accelerator comprising: (1) from 0.01 to 0.5g/l of nitrite ion, (11) from 0.05 to 5g/l of m-nitrobenzene sulfonate ion, or (iii) from 0.5 to 10g/l of hydrogen peroxide (base on 100% H2O2); and (d) from 0.01 to 10g/l of colloidal particles having an isolectric point of 3 or less and an average particle diameter of 0.1 or less.