What is the difference between hot-dip galvanized steel pipe and cold-dip galvanized steel pipe?

Hot-dip galvanized steel pipe: Hot-dip galvanized steel pipe is first pickled on the steel parts. In order to remove iron oxide on the surface of steel parts, after pickling, they are cleaned in an aqueous solution of ammonium chloride or zinc chloride or a mixed aqueous solution of ammonium chloride and zinc chloride, and then sent to a hot-dip plating tank. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion, and long service life.

Cold-dip galvanized steel pipe: Although cold-dip galvanized steel pipe is rarely used on a large scale now, since we are talking about the difference, it is natural to introduce it. Cold galvanizing is also called electro-galvanizing. It uses electrolysis equipment to remove oil and pickle, then puts it into a zinc salt solution and connects it to the negative electrode of the electrolysis equipment. Place a zinc plate on the other side of the fitting, connect it to the positive terminal of the electrolysis unit, and turn on the power. Use current to move from the positive terminal to the negative terminal. A layer of zinc is deposited on the pipe fittings, and the cold-plated pipe fittings are processed first and then galvanized.

The difference between hot-dip galvanized steel pipe and cold-dip galvanized steel pipe:

1. Different manufacturing processes

Hot-dip galvanized steel pipe reacts molten metal with the iron matrix to form an alloy layer, which combines the matrix and the coating.
Cold-dip galvanized steel pipe is a cold-dip galvanized coating that mainly performs anti-corrosion through electrochemical principles.

2. Different equipment required

Hot-dip galvanized steel pipe: pickling equipment, bottom pull annealing furnace or bell annealing furnace.
Cold galvanized steel pipe: electrolysis equipment.

3. Different performance
Hot-dip galvanizing: durable anti-corrosion, standard quality hot-dip galvanizing anti-rust thickness makes it have excellent durability; the coating has strong toughness, and the hot-dip galvanizing layer forms a unique smelting metal structure. The structure can withstand mechanical damage during transportation and use.

Cold galvanizing: has excellent environmental performance. Most cold galvanizing solvents and diluents do not contain highly toxic organic solvents. The cold galvanizing process also reduces the volatilization of organic solvents, reduces drying energy consumption, and is beneficial to environmental protection.

4. Different thicknesses of galvanized layers
The zinc layer of hot-dip galvanized steel pipe is relatively thick, with a thickness of more than 10um. Although the surface is bright, it is rough and there will be sequins.
The zinc layer of electro-galvanized (cold-dip galvanized steel pipe) is very thin. As long as the thickness is 3-5um, although the surface is smooth, it will appear dark and dirty, with good processing performance and insufficient corrosion resistance.

5. Different applications
Hot-dip galvanized steel pipes are widely used in power towers, communication towers, railways, highway protection, street light poles, ship components, building steel structure components, substation ancillary facilities, light industry and other fields due to their good anti-corrosion properties.
Cold-dip galvanized steel pipe is the main development direction of environmentally friendly heavy-duty anti-corrosion coatings.

Read more: Seamless Galvanized Pipe