Process flow: loading → electrochemical degreasing → hot water washing → cold water washing → acid etching → water washing → activation → rolling galvanized iron alloy → empty tank to remove the liquid → cleaning → cleaning → roller barrel passivation → cleaning → light emitting → cleaning → passivation → hot sealing → drying → drying
1.Pre plating treatment
- Electrochemical degreasing
- Acid etching
HCL 500mL/L, additive 40-50MLL/L, water 450-460mL/L, room temperature min2-5
Features: Low acidity, no acid mist, no environmental pollution, good effect, both rust and mild oil degrease, and lower cost than acid cleaning.
HCI (A · K) 10-20ml/L, remaining water, room temperature 2-3 minutes
Features: It can remove floating rust in front of the groove of the roller plated parts, ensure good adhesion between the substrate and the coating, and stabilize the pH value of the solution
(1) Formula composition
Zncl240-70g/L, kci or NaCI (refined salt) 180-230g/L, FPSO4-7H2O5-12g/L, ZF-A cylinder opening agent 15-20mL/L, ZF brightener 6-12mL/L, ZF-B adjusting agent 5-10mL/L, pH 3.5-5.5-60 ℃, 100-300A/poke, the ratio of Zn to Fe anodes is (10-12): 1. Roll plating does not use pure iron anodes, the barrel speed is 8-10r/nvn, and the iron content of the coating is 0.2% -0.8%
(2) Solution preparation
Firstly, dissolve ZnCL2 and KCI in 1/2 volume of water, add 1g/L zinc powder and 1g/L powdered activated carbon respectively, and treat the filter tank; Adjust the pH to 4 with reagent hydrochloric acid; Dissolve Weissner’s solution in water and add it to a container containing FeSO4 solution dissolved in 10 times water. The solution immediately becomes turbid, and when it is clear, transparent, and colorless, add it. Dilute ZF-A cylinder opening agent and ZF brightness agent with 1-2 times water (cold water in summer and autumn, hot water in winter and spring), and add ZF-B adjusting agent with 3 times water; Add water to the required volume, stir evenly, and electrolyze for 4 hours for trial plating
The zinc plating layer can improve the brightness of the coating by emitting light through nitric acid, while the zinc iron alloy emits light through nitric acid. The purpose is to remove the extremely thin impurity film on the surface of the coating, making the bright coating clearer and ensuring good adhesion between the coating and the passivation film. This passivation process can obtain silver white, blue white, colored, military green to black appearance passivation films with very low chromium salt content, with a chromium salt content of 0.5-5g/L. After passivation, there is no need to clean. No environmental pollution.