There are two kinds of galvanizing process for color coated galvanized sheet, which are hot galvanizing and cold galvanizing. Different galvanizing processes and effects are also different. What are the specific differences between them? How should we
make correct identification when choosing? With these questions, please see the explanation in this article.
1. The hot dip galvanizing process of color coated galvanized sheet is generally thicker than 10um, which has strong anti-corrosion ability. So it is a common zinc plating process. However, the cold galvanizing is very thin, about 3-5um. The surface of
hot-dip galvanizing is rough and bright. In serious cases, there are zinc flakes. The electroplating is smooth and gray (dirty). The galvanized steel sheet produced by electroplating method has good processability. However, the coating is thinner and
its corrosion resistance is not as good as that of hot dip galvanized sheet. The amount of galvanizing is very small, only galvanizing on the outer pipe wall (hot-dip galvanizing - both inside and outside), only 10-50g / m2. Its corrosion resistance is
much different from that of hot-dip galvanizing.
2. There is a great difference in the amount of galvanizing between hot-dip galvanized sheet and cold-dip galvanized sheet. The zinc content of hot dip galvanizing can not be too small, which is generally
50-60g / m2 on both sides. The zinc coating of cold galvanized sheet can be very thin, up to 15g / m2. However, if the coating thickness is required, the speed of the production line is very slow, which is not suitable for the process characteristics
of the modern production line, which is generally about 10 g / m2. Because of this, the production of cold galvanized sheet is greatly restricted.
3. There are fundamental differences in the coating structure between hot-dip galvanized sheet and
cold-dip galvanized sheet. There is a layer of brittle compound layer between the pure zinc coating and the steel strip substrate of hot-dip galvanized sheet. Most of the pure zinc coating forms zinc flake when it crystallizes, and the coating is uniform
and has no pores. However, the zinc atoms in the cold galvanized layer are only deposited on the surface of the steel strip, and they are attached to the surface of the steel strip by physical action. There are many holes to air, and it is easy to cause
pitting corrosion due to corrosive medium. Therefore, hot-dip galvanized sheet is more corrosion-resistant than cold-dip galvanized sheet.
4. The heat treatment process of hot-dip galvanized and cold-dip galvanized sheet is also completely different. Generally, the hot-dip galvanized sheet is made of cold and hard plate, which is continuously annealed and hot-dip galvanized on the
galvanizing line. The steel strip is heated in a short time and then cooled, so its strength and plasticity are affected to a certain extent, and its stamping performance is worse than that of the same cold-rolled plate after degreasing and annealing
in a professional production line. Cold galvanized sheet is made of cold-rolled sheet, which basically guarantees the same processability of cold-rolled sheet, but its complicated process also increases the production cost. In short, the production cost
of hot-dip galvanized sheet is lower, and its application range is wider, and it has become the main variety of color coated galvanized sheet market.