| 摘要 |
PURPOSE:To impart phosphate treating property and corrosion resistance after painting by a method wherein an oxidized film on a surface of a steel plate formed by decovering said steel plate at a high temp. of from an annealing temp. to 200 deg.C after box annealing is removed by pickling and rapidly cooled and, thereafter a suspension containing an insoluble phosphate of a divalent or a trivalent metal is blown thereon under pressure. CONSTITUTION:A steel plate is decovered at a high temp. of up to 200 deg.C after box annealing and cooled by a cooling medium to form an oxidized film on a surface thereof. The resultant oxidized film is removed by pickling by using an immersing or a spraying means and washed. Subsequently, a suspension containing an insoluble phosphate of a divalent or a trivalent metal is blown thereon under pressure to condition the surface thereof. As a divalent metal salt, Zn3(PO4)2, Ca(PO4)3 are used and, as a trivalent metal salt, AlPO4, FePO4 are used. |
