In the production process of using alkaline zinc plating brightener, sometimes the low area of the workpiece will turn black, what should I do?
Bigolly Technology made an analysis based on the field experience and the characteristics of the product's alkaline zinc plating brightener BZ-515,There are three main reasons:
1. Lead ion pollution.When the lead ion impurity in the alkaline galvanizing solution exceeds 15mg/L, the dispersing ability of the plating solution will decrease significantly, and black or gray streaks will appear on the galvanized layer after light emission by dilute nitric acid.Lead ions are mainly brought in by inferior zinc anode plates. In order to prevent lead pollution, zinc anodes need to use 0# zinc or 1# zinc.
2. Iron ion pollution.When the iron ion content in the alkaline zinc solution is as high as 50mg/L, if the iron ion content is further increased, colloidal flocs will appear in the plating solution, and the galvanized layer will appear purple-blue after passivation, and it is prone to foaming.Iron ions are mainly brought in by inferior sodium hydroxide or workpieces.Therefore, white bead alkali should be used, and red sodium hydroxide should not be used. The workpiece should be thoroughly cleaned when it enters the galvanizing tank, and the area ratio of cathode and anode should be adjusted. Use nickel plate or nickel-plated iron plate as anode as much as possible.
3. Copper ion pollution.When the copper ion content in the alkaline galvanizing solution reaches 20 mg/L, the obtained galvanized layer is rough, the brightness decreases, and the bright current density range gradually narrows with the increase of the copper ion content.Copper ions are mainly brought in by hooks and scrubbing copper rods.
Therefore, in the production process of using alkaline galvanized brightener, the blackening of the low current density area of the workpiece is generally caused by the contamination of metal ion impurities.During production, these impurities should be avoided as much as possible into the galvanizing tank, and the plating solution should be maintained regularly to reduce the occurrence of failures.