Category: galvanized steel sheet
By Alisajpq, 2019-05-12
Low cost hot dip galvanized steel coil factory shares the reason for the hot-dip galvanizing storage time
The defects of hot-dip galvanized sheet mainly include: shedding, white rust, and black spots, scratches, passivation spots, zinc particles, thick edges, uneven thickness of zinc layer, and roll printing.
The main reasons for the zinc layer of hot-dip galvanized sheet are: surface oxidation, silicon compound, foreign matter in cold-rolled emulsion, low temperature in strip steel, endless evaporation of oil, low aluminum content in zinc pot, and too fast unit speed The reduction is not sufficient, the residence time in the zinc solution is too short, and the plating layer is thick.
Causes of white rust and dark spots:
1. The main causes of white rust are poor passivation, insufficient or uneven passivation film thickness.
2. The surface is not oiled or the surface of the strip remains moisture.
3. The surface of the strip contains moisture when coiling.
4. Passivation is not completely dried.
5. Get wet or rain when transporting or storing.
6. The finished product storage time is too long; the galvanized coil plate is in contact with or stored together with other corrosive media such as acid and alkali.
The finished galvanized sheet is allowed to be stored for up to three months in the warehouse to avoid oxidation for a long time, and the black spot is further oxidized by white rust.