Cold rolling and hot rolling processes are two forming methods for steel. Cold-rolled products have higher dimensional accuracy and are suitable for more applications with high dimensional requirements. Cold rolling is performed below the crystallization temperature and is controlled by different types of rolls. The basic products are cold-rolled plates and coils, and other shapes such as cylinders, I-beams, and pipes can also be formed.
Can
cold rolled steel products be galvanized? The answer is yes, they are two processing methods with different purposes, one is shaping and the other is anti-corrosion. The only limitation of galvanized steel is that it cannot be used in high temperature conditions, and if the surface is scratched, the zinc layer will lose its protection at the scratched location.
Galvanized steel products can be produced with both cold-rolled steel and hot-rolled steel. Generally, hot-rolled steel has better yield strength than cold-rolled steel because the cold-rolling process destroys the grain structure of the steel, while hot-rolling improves the grain structure. structure. Cold rolled steel has a better surface condition than hot rolled steel. Customers should choose appropriate steel materials according to different uses.
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Cold rolling and galvanizing are not mutually exclusive, in fact cold rolled steel can be galvanized. This is because cold rolling is a steel-forming technique, while hot-dip galvanizing is a technique for treating steel to prevent corrosion. Galvanized steel generally has better corrosion resistance but is less suitable for high temperature conditions. Although it can be easily damaged or scratched, the zinc layer will continue to provide corrosion protection despite damage to its surface.
The mechanism of zinc coating protecting steel plates
In the atmosphere, zinc's corrosion resistance is much stronger than steel. Under normal conditions, zinc's corrosion resistance is several times that of steel.
1), physical effects:
The zinc coating on the surface of the steel plate blocks the contact between the steel plate and the corrosive medium outside, making the steel plate immune to the corrosive effect of the corrosive medium.
2), electrochemical effect:
When the galvanized steel plate substrate and the zinc coating are exposed to corrosive media at the same time (such as scratches and cuts in the zinc coating), since the electrode potential of zinc (-0.726V) is lower than the electrode potential of iron (-0.44V), Zinc acts as an anode and steel acts as a cathode, so zinc corrodes preferentially and protects the substrate. This is called the sacrificial anode protection effect of zinc.
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