Under high temperature, high humidity and airtight conditions, zinc is in contact with volatiles released from wood, paint and wood. Zinc has the tendency to grow filamentous single crystals, commonly known as "long hair".

After chromate passivation, the corrosion resistance of galvanized steel pipe can be improved by 6-8 times. Therefore, galvanizing passivation treatment is an essential step. Organic dyeing on the passivation film can be used for product protection - decorative electroplating.

In order to reduce the zinc coating thickness of galvanized steel pipes and improve corrosion resistance, the following two measures have been taken at home and abroad. One is to use blue, green, military green and black passivation instead of ordinary iridescent passivation film, especially to improve the corrosion resistance of military green passivation film;

The second is to replace the pure zinc coating with thin Zn-Fe alloy containing 0.3% - 0.6% iron or Zn-Ni alloy containing 6% - 10% nickel, which improves the corrosion resistance by more than three times, and is widely used to replace zinc plating on automobile steel plates.

The standard potential of zinc is negative than that of iron, which is anodic electroplating for steel and can provide reliable electrochemical protection. Zinc can be selected as the protective layer for steel products used in industrial atmosphere, rural atmosphere and marine atmosphere, and its protective life is roughly proportional to the thickness of the zinc layer. In the atmosphere polluted by industrial exhaust gas, the corrosion resistance of zinc coating is better than that of cadmium coating, but the opposite is true in the sea or sea water.