The pickling and rinsing process before the production of hot-dip galvanized sheet is very strict. Only in this way can high-quality and qualified production be produced.
1. The acid pool must be rinsed clean before preparing the pickling solution. No rust, silt and other attachments are allowed to be stored in the pool.
2. The pickling solution is diluted hydrochloric acid, the working concentration is 40-200 g/L solution, and the working temperature is normal temperature.
3. Preparation of pickling solution: use industrial hydrochloric acid with a concentration of 28% or more and add water at a ratio of 2:1 to prepare a pickling solution with a solution concentration of 200 g/l. Generally, no acid is added during use until its concentration drops to 40/ When the content of ferrous chloride rises to 200 g/liter of solution, the waste acid enters the neutralization tank for treatment, and discharges after reaching the standard (discharge requirements are stipulated by the environmental protection department). If the content of ferrous chloride is less than 200 g/L and the concentration of hydrochloric acid is less than 40 g/L, you can add concentrated hydrochloric acid to continue using it.
4. The pickling solution is tested twice a week, and the measurement results are reported to the workshop and the head teacher to guide the pickling operators.
5. The pickling time should be related to the surface oxide layer of the hot-dip galvanized steel sheet and the pickling concentration, generally 30-40 minutes. During the pickling process, move the workpiece up and down two to three times, and propose the liquid level to check the pickling Quality. For the surface that is not pickled locally, it can be removed with a grinding wheel, steel wire brush and other tools and then pickled clean, so that no residual oxide layer and other contaminants adhere to the surface of the steel, and the surface is gray and shiny.
6. The hot-dip galvanized steel sheet qualified for pickling must enter the rinsing process tank and rinse with running water to remove the pickling solution remaining on the surface. After the plating parts are hoisted from the rinsing tank, they should stay on the tank for no less than 15 seconds, and then the surface area will be dropped. After water, immediately enter the plating flux tank for solvent treatment.
7. The rinsing water should be clear, keep flowing and keep clean, and the PH value should be greater than 6.
