Abstract: The present invention provides a method of correcting warpage of a steel strip caused by a current-carrying roll and an opposite backup roll, which hold the steel strip therebetween, in a horizontal electroplating line, wherein the opposite backup roll is formed to be smaller than the current-carrying roll, and the backup roll is offset relatively to the opposite current-carrying roll in the movement direction of the steel strip by a constant value predetermined according to operation conditions. The offset amount is preferably within the range of 5 to 35 mm.

Abstract: A method of dissolving zinc oxide in which, to perform continuous zinc-system electroplating of a steel sheet using an insoluble anode, particularly continuous zinc-nickel alloy electroplating, a dissolution bath is provided in a circuit for a sulfuric acid plating liquid, and zinc oxide is dissolved in the plating liquid in the dissolution bath. The amount of zinc oxide thrown in is controlled during dissolution of zinc oxide so that the pH of the plating liquid at an outlet of the dissolution bath does not exceed 2.3.

Abstract: An apparatus for continuously dissolving metal powder for use in plating includes a dissolving tank for dissolving metal powder for used in plating solution in a solvent, a filter for separating the solution containing undissolved residue into an undissolved residue and a filtrate, a recovery tank of the filtrate, and a plating solution storing tank for supplying recovered filtrate to a plating tank. The filter is a porous substance having a plurality of liquid passages in the axial direction thereof, and the filter is provided with a circuit for returning a liquid solution containing the undissolved residue passed through the passages to the dissolving tank and a pipeline for leading the filtrate to the recovery tank.A method of dissolving a nickel metal, which has a specific surface of 0.003 m.sup.2 /g or more, is dissolved with the use of the above-described apparatus.