When we use chrome plating additives, the workpieces can be brightly plated with good coverage ability of chrome plating. However, sometimes the workpieces produced are poorly plated, what is the reason for this?
1. The ratio of chromic anhydride to sulfuric acid in the plating solution is not within the process range. In general decorative chromium plating process, the ratio of chromic anhydride to sulfuric acid is 200:1. chromic anhydride concentration increases, the conductivity of the plated layer increases, and the covering ability of the plated layer increases, but the current efficiency of the cathode decreases. When sulfuric acid is insufficient, the chromium plating layer is relatively rough; when the sulfuric acid content is high, there is no chromium in the low current density area of the plating layer. Therefore, their contents should be strictly controlled and their ratio should be controlled in the production process.
2. Mismatch of current density. The current density of chromium plating has a great relationship with the performance of the plating solution and the appearance of the plated layer. When the current density is low, the current efficiency of chromium plating is low and the brightness of the plated layer is poor. Bigelow suggests that the current density of chromium plating should be controlled above 15A/dm2.
3. The concentration of trivalent chromium in the plating solution is too high. When the concentration of trivalent chromium in the plating solution is high, the colloidal film formed on the chromium layer is thick and dense, sulfuric acid is difficult to dissolve, and the chromium layer can only grow on the original grain, resulting in rough crystallization of the plating layer, darkening, and lack of luster.
4. The plating solution is too high in iron, copper, zinc and other impurities. Iron ions in the plating solution mainly comes from the accumulation of workpiece drop tank and workpiece dissolution, when the plating solution iron impurity content is greater than 8g/L, the conductivity of the plating solution is reduced, the current is unstable, and the bright range of the plating layer is narrowed. And when the copper impurity in the plating solution is more than 5g/L and zinc impurity is more than 3g/L, it will obviously reduce the covering ability and bright range of the plating layer.
About us
Guangdong Bigely Technology Co., Ltd. ,founded in 2003, is a high-tech enterprise integrating R & D，production, sales and service, specializing in the production of electroplating additives. As a famous electroplating additives source manufacturer in China, Bigely Technology is a national high-tech enterprise with a strong research and development team, which has over 10 engineers with more than 20 years' working experience in the electroplating industry.
If you need our high-quality electroplating additives, please contact us. We can provide you samples for test, and also provide a series of services.
