In the process of using chromium plating additives, sometimes the coverage of the coating is poor, which affects the appearance and performance quality of the workpiece coating.So what causes this phenomenon?
Bigolly Technology made an analysis based on the field experience and the characteristics of the product chromium plating additive Cr-9,There are 7 main reasons:
1. The concentration of chromic anhydride in the plating solution is too low.When the concentration of chromic anhydride in the plating solution is too low, the covering ability of the coating will be poor, and defects such as nickel leakage will also occur.Therefore, in the production process, the concentration of chromic anhydride in the bath and the ratio of chromic anhydride to sulfuric acid should be analyzed and adjusted.
2. The sulfate content in the bath is too high or too low.The sulfate content in the plating solution should be regularly analyzed and adjusted.When the sulfate content is high, the concentration of chromic anhydride can be appropriately increased or barium carbonate can be used to remove it. Generally, 2g/L of barium carbonate can remove 1g/L of sulfate.When the sulfuric acid is too low, the concentration of sulfuric acid should be appropriately increased to within the process range.
3. The content of trivalent chromium in the bath is too high.If the content of trivalent chromium in the bath is too high, it will not only affect the covering ability of the coating, but also cause fog and blue film.Therefore, the content of trivalent chromium in the bath should be controlled at 2~5g/L.
4. The chloride ion content is too high.When the chloride ion content in the plating solution exceeds 0.5g/L, the covering capacity, current efficiency and the bonding force of the coating will be significantly reduced, and the chrome coating will also appear foggy and blooming.Chloride ions in the plating solution can be removed by electrolysis.
5. An oxide film is formed on the surface of the anode plate.A layer of oxide film is formed on the surface of the anode plate, which will reduce the current efficiency and make the covering ability of the coating layer worse.We can use dilute hydrochloric acid or sodium hydroxide solution to clean the anode plate.
6. The current density is too small or the temperature of the plating solution is too low.The current density and bath temperature have a great influence on bath properties (such as coverage ability, current efficiency, etc.).Therefore, parameters such as current density and temperature should be strictly controlled within the process range.
7. The nickel layer is passivated.The passivation of the nickel layer on the surface of the workpiece before chrome plating will cause uneven chrome plating.The passivated nickel layer can be activated with a 5% sulfuric acid solution or anodized in lye to activate the surface.
Therefore, we should pay attention to the above 7 points in the process of using chromium plating additives to avoid the phenomenon of poor coating ability and reduce the occurrence of failures.If you are interested in chromium plating additives, please contact Bigolly customer service, you can get free samples and detailed technical information!
If you want to know more about chrome plating, you can click to view the "Electroplating-encyclopedia".