How should the solution concentration, time and temperature of aluminum alloy zinc sinking solution be controlled to ensure that the galvanized layer provides a good bond for subsequent plating?
Influence of solution concentration
Aluminum and aluminum alloys in the process of zinc sinking, the concentration of the solution determines the size and densification of the grains, if the concentration of the solution is low, the deposit is relatively coarse and treelike, and when the concentration of the solution is high, the deposit crystallization is more detailed. The latter compared with the former, the bonding force has a considerable increase, but the solution is too thick, the viscosity increases, the loss of banding is larger. When using Bigely aluminum alloy zinc sinking solution BC-22, it is recommended to control the concentration at 20-30% volume ratio if it is a rack plating process.
Temperature impact
During the deposition of zinc, temperature has a great influence on its rate. At higher temperatures, the zinc crystallizes faster and the zinc layer is thicker but rougher. At lower temperatures, the nuclei are gradually formed and the zinc layer is thinner but more uniform and detailed. It is recommended that the temperature be controlled between 16-46°C, which will result in a denser zinc dipping layer on the aluminium and aluminium alloys.
Timing impact
In the actual production process, the zinc layer will be deposited faster in the first twenty seconds, slow down after twenty seconds, and become deteriorated after reaching more than two minutes. This is the reason why a zinc sinking time of 0.5 to 1 minute is appropriate.
Conclusion
Aluminum alloy is affected by its own characteristics, the substrate and the plating layer does not have enough bonding force, so it is indispensable to carry out pre-treatment processes such as zinc sinking, we can use Bigely aluminum alloy zinc sinking solution BC-22 for zinc immersion treatment, so that the subsequent either electroless nickel plating, or nickel electroplating, can do a good brightness and good bonding force.
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