During the process of using trivalent chromium black passivation agent for galvanizing, we sometimes find flow marks on the surface of the produced workpiece. What is the reason for this?
Based on on-site experience and the characteristics of the trivalent chromium black passivating agent BZ-216 and sealing agent 76, Bigley Technology has analyzed the following three main points:
1. There are burrs at the hole position of the workpiece. When burrs appear at the holes of the galvanized layer, black passivation and sealing treatment are prone to water droplets, and after aging treatment, flow marks will appear on the surface of the coating. Therefore, during the galvanizing process, the coating condition on the surface of the workpiece should be strictly checked. When burrs are found, the plating solution should be promptly treated to ensure good quality of the coating. This way, the coating quality of the workpiece after black passivation is also good.
2. The concentration of sealant is too high. During the process of using sealant 76, the concentration range of the working solution is 100-250ml/L, which can ensure the uniform and dense sealing film layer. When the concentration of the sealing agent is too high, the working fluid will be relatively viscous. After the workpiece is sealed, the water droplets in the hole or hook position flow down slowly. After aging treatment, flow marks will appear on the surface of the coating. Therefore, the concentration of the sealing agent should be controlled within the process range during the production process.
3. The temperature of the sealant is too low. During the process of using sealing agent 76, the temperature range of the working fluid is 30-50 ℃. In winter or when the working fluid is not heated, the temperature of the working fluid is lower, and the working fluid will be more viscous. After the workpiece is sealed, the water droplets in the hole or hook position flow down slowly, and after aging treatment, flow marks will appear on the surface of the coating. Therefore, the stability of the sealing agent should be controlled within the process range during the production process.
Therefore, when using the zinc plated trivalent chromium black passivation agent BZ-216, there may be flow marks on the surface of the workpiece, we should pay attention to the above three points to solve the problem as soon as possible and improve production efficiency. If you are interested in the trivalent chromium black passivation agent BZ-216 for galvanizing, please contact Bigley customer service to obtain free samples and detailed technical information!
If you want to learn more about galvanizing, you can click to view the "Common problem".
