Hot galvanized sheet surface black why?
2023-05-08 14:42:49.892
Release time:
2023-05-08
Hot galvanized sheet black cause:
A. The purity of the galvanized layer is not enough, the metal impurities on the zinc surface constitute a galvanic cell, and when it is favorable for hydrogen evolution, it is easy to produce black spots on the surface of the zinc layer.
b. When the content of copper, iron, arsenic and other impurities in the galvanized layer is high, after passivation treatment, these impurities appear black.
c. The surface of the original plate is not sufficiently treated with dirt, forming residue, so that some parts can not be plated with zinc, resulting in problems in the galvanized layer and easy to fall off, resulting in black spots.
d. When galvanized, there is leakage plating, which is easy to form black spots during post-treatment.
e. The galvanized liquid contains residue or small black ash (carbon or carbon compounds), adheres to the surface of the zinc layer or resides in the zinc layer, and is firmly combined with the zinc layer. Black spots can be seen on the finished galvanized sheet.
f. Abrasive black spots. Caused by rough operation in the process of transportation and stacking.
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