(1) Poor passivation, insufficient or uneven passivation film thickness;
(2) The surface is not oiled or there is residual moisture on the surface of the strip;
(3) The surface of the strip steel contains moisture during coiling;
(4) The passivation is not completely dried;
(5) Moisture or rain during transportation or storage;
(6) The finished product has been stored for too long;
(7) The galvanized sheet is in contact with or stored together with other corrosive media such as acid and alkali.
