PRODUCTION OF SURFACE TREATED STEEL PLATE OF HIGH RUST PREVENTION FOR WELDED CAN

PURPOSE:To convert an alloy layer of a tin plate to structure of high rust prevention and improve the corrosion resistance of the thinly coated tin plate by plating tin on a nickel plated steel plate prior to annealing and further subjecting the same to a chromate treatment then to a tin melting treatment. CONSTITUTION:After a steel plate made by cold-rolling of an ingot material or the like to about 0.15-0.33mm. thicknesses is degreased, it is subjected to nickel plating of 0.02-0.2g/m by using a watt bath or the like then to annealing at about 550-720 deg.C after rinsing and drying; thereafter, this is subjected to skin pass rolling then to tin plating after degreasing and pickling. A halogen bath or the like is used for the tin plating, and the stuck amount of tin is limited to 0.05-1.5g/m , so that the chromate is buried like islands in the tin layer in the stage of reflowing and the iron-tin alloy is made finer. The steel plate tin-plated in this way is chromated in an aq. sodium dichromate soln. at 0.3- 10Coulomb/dm quantities of electricity, after which it is subjected to a tin melting treatment then to sealing by a chemical treatment.