(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 conductor, and the current distributed to the surface of the workpiece is too small.
(3) The workpiece contains high carbon content. High-carbon steel and cast iron parts will lower the hydrogen evolution potential, accelerate the hydrogen evolution on the surface of the workpiece, and reduce the current efficiency.
(4) The workpiece is tied too tightly. When galvanizing, the parts are partially shielded, resulting in too thin coating.
(5) The bath temperature is low. When the bath temperature is low, the current density and deposition rate of the coating will decrease accordingly.
(6) The sodium hydroxide content in the plating solution is too high. When the sodium hydroxide content is high, the current efficiency will decrease accordingly.
(7) The content of additives in the plating solution is low. Low additive content will affect the dispersion ability, and the coating is too thin.
(8) The area of electroplated parts is underestimated, and the current density distributed during electroplating is too small.
(9) If the suspension of the workpiece is improper, and the distance between the workpiece and the zinc anode is too large, the position should be adjusted.
(10) The workpiece is corroded. When the hydrogen evolution potential decreases, the current efficiency of accelerating hydrogen evolution on the surface of the workpiece decreases, which affects the deposition rate of zinc. Appropriate amount of corrosion inhibitor should be added to the pickling solution. If the local oxide scale is too thick, it should be removed mechanically first, and more checks should be made during pickling.
(11) Anode passivation. The reduction of the effective area affects the normal distribution of the current.
(12) The sodium hydroxide content is low. If the sodium hydroxide content is low, the current density is not high and the anode is passivated.