In the production process of alkaline galvanizing, sometimes the brightness of the coating of the workpiece is not enough, we will add more alkaline galvanizing brightener to improve the brightness of the galvanizing layer.And sometimes the coating is not bright, even if the brightener is added, the brightness of the coating is not improved, why is this?
1. Improper operation of the plating solution.If the temperature of the bath is too high or the cathode current density is too small, the adsorption of the brightener is relatively weak, and the brightness of the coating will be darker.Therefore, we need to select the appropriate current density at the appropriate temperature to refine the crystallization of the coating and improve the brightness.
2. The proportion of zinc alkali in the bath is wrong.When the zinc content in the bath is too high and the alkali content is too low, the brightness of the galvanized layer will be uneven, and sometimes the phenomenon of yin and yang surfaces will appear.Therefore, we should strictly control the concentration of zinc and alkali in the alkaline zinc plating solution to keep the electroplating solution with good electrochemical properties and obtain an excellent galvanized layer.
3. There are too many metal impurities in the plating solution.There are no other strong complexing agents in the alkaline zinc plating solution, and the plating solution is sensitive to impurities, and metal impurities such as copper, lead, iron, and cadmium are easily accumulated in the production process.When lead>15mg/L, copper>50mg/L and iron>50mg/L in the electroplating solution, the zinc coating will appear dark, black or black stripes.Therefore, in the production of galvanized, we should regularly use sodium sulfide or zinc powder to treat metal impurities in the plating solution.
Therefore, the brightness of the alkali zinc workpiece coating is not enough,it is not necessarily that the concentration of alkaline galvanized brightener is insufficient,and the operating conditions of the plating solution and the influence of metal impurities should be considered.