Method for circulating iron-based electroplating solution, method for manufacturing iron-based electroplating solution, and method for manufacturing alloyed hot-dip galvanized steel sheet

Abstract

A method for circulating an iron-based electroplating solution, a method for manufacturing an iron-based electroplating solution, and a method for manufacturing an alloyed hot-dip galvanized steel sheet, which can be used to obtain an iron-based electroplating solution that is stably capable of operating with high electrolytic efficiency without sludge contamination and is capable of being power-saved without requiring large-scale equipment. In the first method, an iron-based electroplating solution used in an electroplating cell for iron-based electroplating is circulated and adjusted. The iron-based electroplating solution used in the electroplating cell is caused to pass through at least a reduction tank, a vertical centrifugal solid-liquid separation device, and a final adjustment tank in this order, and then is put into the electroplating cell. In the reduction tank, an iron source for reduction according to a concentration of Fe 3+ in the iron-based electroplating solution transferred to the reduction tank is put.

1 . A method for circulating an iron-based electroplating solution, in which an iron-based electroplating solution used in an electroplating cell for iron-based electroplating is circulated and adjusted, the method comprising causing the iron-based electroplating solution used in the electroplating cell to pass through at least a reduction tank and a vertical centrifugal solid-liquid separation device in this order to perform a process, then putting the iron-based electroplating solution into the electroplating cell; and
 wherein, in the reduction tank, an iron source for reduction according to a concentration of Fe 3+  (Fe trivalent ion) in the iron-based electroplating solution transferred to the reduction tank is put.   
     
     
         2 . The method for circulating an iron-based electroplating solution according to  claim 1 , wherein, in the reduction tank, sulfuric acid is put such that a PH of the iron-based electroplating solution in the reduction tank is maintained at 2.3 or less. 
     
     
         3 . The method for circulating an iron-based electroplating solution according to  claim 1 , wherein a nitrogen gas is sealed in the reduction tank. 
     
     
         4 . The method for circulating an iron-based electroplating solution according to  claim 1 , wherein the vertical centrifugal solid-liquid separation device includes a screw outer tube that differentially rotates a solid and a liquid in a raw solution such that the solid and the liquid are centrifugally separated by a difference in specific gravity, and a screw provided in the screw outer tube, a rotary shaft of the screw is formed in a tubular shape such that the raw solution is derived from the screw into the screw outer tube, and a diffusion opening portion is formed on a side surface of the rotary shaft. 
     
     
         5 . The method for circulating an iron-based electroplating solution according to  claim 1 , wherein the iron-based electroplating solution is processed by the vertical centrifugal solid-liquid separation device, and then caused to pass through a final adjustment tank, and in the final adjustment tank, the concentration of Fe 3+  (Fe trivalent ion) in the iron-based electroplating solution is adjusted to be 4.0 g/L or less. 
     
     
         6 . The method for circulating an iron-based electroplating solution according to  claim 5 , wherein, in the final adjustment tank, a PH of the iron-based electroplating solution is adjusted to 2.0 to 2.3. 
     
     
         7 . The method for circulating an iron-based electroplating solution according to  claim 5 , wherein, in the final adjustment tank, a solution temperature of the iron-based electroplating solution is adjusted to 40° C. to 55° C. 
     
     
         8 . The method for circulating an iron-based electroplating solution according to  claim 1 , wherein the iron-based electroplating solution is processed by the vertical centrifugal solid-liquid separation device, and then caused to pass through a final adjustment tank, and in the final adjustment tank, a concentration of Fe 3+  (Fe trivalent ion) in the iron-based electroplating solution is adjusted to 2.0 g/L or less, a PH of the iron-based electroplating solution is adjusted to 2.0 to 2.3, and a solution temperature of the iron-based electroplating solution is adjusted to 40° C. to 55° C. with sulfuric acid and pure water. 
     
     
         9 . A method for manufacturing an iron-based electroplating solution, the method comprising:
 manufacturing an iron-based electroplating solution by performing circulation and adjustment by the method for circulating an iron-based electroplating solution according to  claim 1 .   
     
     
         10 . A method for manufacturing an alloyed hot-dip galvanized steel sheet, the method comprising:
 performing an iron-based electroplating process on a steel sheet using the iron-based electroplating solution manufactured by the method for manufacturing an iron-based electroplating solution according to claim  9 .