The turbidity of the acidic tin plating solution is frequently encountered, and the problem of slight turbidity is not significant. The excessive turbidity of the plating solution causes the quality of the tin plating layer to deteriorate, resulting in a decrease in the brightness and deep plating ability of the plating layer. The main reason for the turbidity of the bath is the hydrolysis of divalent tin, the polymerization of additives, and the incorporation of foreign metal impurities. This is largely aggravated by the rising temperature of the bath and the anode current density cannot be too high. . Therefore, it is necessary to keep the bath working under conditions of low temperature and anode area greater than the area of ​​the cathode. The turbid tin plating solution can be stirred thoroughly with powdered activated carbon of about 5 g/L, and then a coagulating agent (available in a commercial product or polyacrylamide) of about 0.19/L can be stirred and precipitated and then filtered.