| 摘要 |
<p>PV 27776/28515/A A continuous process of producing a phosphate coating on a ferrous metal substrate which comprises treating the ferrous metal substrate with an acidic solution of zinc phosphate in the presence of chlorate ions and adding to the solution as coating proceeds a proportion of a rapid-acting secondary oxidant for ferrous ion selected from alkali metal nitrites, ammonium nitrate, hydrogen peroxide, compounds which liberate hydrogen peroxide under acidic conditions, sodium hypochlorite and peroxy diacid salts, which proportion is sufficient to maintain the concentration of ferrous ion at less than 112 parts per million parts of the solution, there being present in the acidic solution when in the steady state a proportion of the said secondary oxidant of from 0 to 0.6 millimoles per litre of the solution.</p> |
