·Degreasing can be done by chemical degreasing or water-based metal degreasing cleaning agent until the guardrail is completely soaked with water.
· For pickling, H2SO4 15%, thiourea 0.1%, 40~60℃, or HCl 20%, hexamethylenetetramine 1~3g/L, 20~40℃ can be used for pickling. The addition of corrosion inhibitors can prevent excessive corrosion of the substrate.
·The immersion flux maintains a certain activity on the guardrail before immersion plating to enhance the combination of the coating and the substrate. NH4Cl15%~25%, ZnCl22.5%~3.5%, 55~65℃, 5~10min. In order to reduce the volatilization of NH4Cl, glycerol can be appropriately added.