The common factors affecting galvanization are the following:
(1) The pretreatment is not thorough. There is an oxide film on the surface of the workpiece, which affects the normal deposition of zinc.
(2) Poor conductivity. The current is consumed on the wire, and the current distributed to the surface of the workpiece is too small.
(3) The carbon content of the workpiece is high. High carbon steel, cast iron, etc. will reduce the potential for hydrogen evolution, accelerate hydrogen evolution on the surface of the workpiece, and reduce current efficiency.
(4) The workpiece is too tightly bound. During galvanizing, the workpiece is partially shielded and the coating is too thin.
(5) The bath temperature is too low. When the temperature of the plating solution is low, the current density distributed correspondingly decreases, and the deposition speed of the plating layer is also necessarily reduced.
(6) The sodium hydroxide content in the plating solution is relatively high. When the sodium hydroxide content is too high, the current efficiency decreases accordingly.
(7) The content of additives in the plating solution is relatively low. The low content of additives will affect the dispersing ability, and the coating layer appears to be too thin.
(8) The area of the plated part is underestimated, and the current density distributed during plating is too small.
(9) Improper method of workpiece suspension, the distance from zinc anode is too large, the position should be adjusted.
(10) The workpiece is too corroded. Decreasing the potential of hydrogen evolution, the current efficiency of the hydrogen evolution acceleration on the surface of the workpiece is reduced, which affects the deposition rate of zinc. An appropriate amount of corrosion inhibitor should be added to the pickling solution. The localized oxide scale is too thick to be removed by mechanical methods, and more checks should be performed during the pickling process.
(11) Anode passivation. The effective area is reduced, affecting the normal distribution of the current.
(12) The sodium hydroxide content is low. If the sodium hydroxide content is low, the current density will not be increased and the anode will be passivated.
The above is the relevant knowledge about hot-dip galvanizing on the surface of U-shaped bolts, I hope to give you a reference when using U-shaped bolts.