6 Points of Difference Between Hot And Cold Galvanizing

Browse through the 6 points of difference between hot and cold galvanizing in our post.

Point 1. Zinc coating

Hot dip galvanizing process is generally thicker zinc layer, about east 10um or more, anti-corrosion ability is stronger. So it is a commonly used galvanizing process, electroplating zinc is very thin, about 3-5um, the surface of hot dip galvanizing is rough, bright, serious zinc flowers, electroplating is smooth, gray (stain). Electroplating method of manufacturing galvanized steel sheet has good processing properties, but the coating is thinner and less corrosion resistant than the hot dip galvanizing process. Cold galvanizing process is galvanized, the amount of galvanization is very little, only the outer wall galvanization (hot plating - both inside and outside), only 10-50g/m2, its own corrosion resistance than the hot dip galvanizing process tube is much worse.

Small Parts Hot Dip Galvaniizng Plant

Point 2. Galvanizing process

Chemical general electro-galvanizing more, for small parts; hot galvanizing process is generally used for power equipment and components, for large parts and equipment.
Electro-galvanization commonly known as cold galvanizing process is the use of electrochemistry, zinc ingots as the anode, zinc atoms lose electrons and become ionic state dissolved into the electrolyte, while the steel strip as the cathode, zinc ions in the steel strip to get electron reduction into zinc atoms deposited on the surface of the steel strip, forming a coating.
The hot dip galvanizing process is to pickle the steel pipe first, in order to remove the iron oxide on the surface of the steel pipe, after pickling, it is cleaned by ammonium chloride or zinc chloride aqueous solution or ammonium chloride and zinc chloride mixed aqueous solution bath, and then sent to the hot dip plating bath.

Point 3. Amount of galvanization

There is a big difference in the amount of galvanization between hot dip galvanizing process and electro galvanizing process. The amount of galvanizing in the hot-dip galvanizing process cannot be too small, generally at least 50~60g/m2 on both sides and up to 600g/m2, while the galvanizing layer in the electro-galvanizing process can be very thin, at least 15g/m2, but the requirement for a thicker layer is slow for the production line, which is not suitable for the process characteristics of modern units, generally up to about l00g/m2. Because of this, the production of electro-galvanizing process is greatly restricted.

Point 4. Coating structure

The hot-dip galvanizing process and the electro-galvanizing process are fundamentally different in terms of coating structure. There is a slightly brittle compound layer between the pure zinc layer and the steel strip substrate in the hot-dip galvanizing process. The zinc atoms of the electroplated zinc layer are only deposited on the surface of the steel strip precipitation, and is attached to the surface of the steel strip by physical action, there are many holes drying, very easy to cause pitting corrosion due to corrosive media, so the hot dip galvanizing process is more resistant to corrosion than the electroplated zinc process.

Tube/Pipe Galvanizing Plant

Point 5. Raw material

The hot-dip galvanizing process is generally based on cold-hard plate as raw material, which is continuously annealed and hot-dip galvanized in the galvanizing line. The electro-galvanizing process uses cold-rolled sheet as raw material, which basically ensures the same processing performance of cold-rolled sheet, but its complex process also increases the production cost. In short, the hot-dip galvanizing process has lower production costs and a wider range of applications, and has also become the main variety of galvanizing process market.

Point 6. Application

Hot dip galvanizing process tube is to make the molten metal react with the iron substrate to produce an alloy layer, thus combining both the substrate and the plating layer. Hot dip galvanizing process has the advantages of uniform coating, strong adhesion, long service life, etc. Most of the regular galvanized pipe manufacturers do not use electro galvanizing (cold plating) in order to ensure quality. Only those small enterprises with small scale and obsolete equipment use electro galvanizing, and of course their prices are relatively cheaper. The Ministry of Construction has formally issued the following order to eliminate the backward technology of cold galvanized process pipes and forbid the use of cold galvanized process pipes for water and gas pipes.
The general galvanizing process used now is the hot-dip galvanizing process, while the electrical wire channels and so on use the cold galvanizing process, the color has a certain difference.

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