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What Is Hot Dipped Galvanized Steel?

Hot dipped galvanized steel (HDG) is a form of galvanized material, which has a tough zinc coating and excellent corrosion resistance. While it is much cheaper than stainless steel. Considering its great durability and shiny surface, it is widely used in many applications, including roofing, wall panels, doors, steel structures, etc. Below let’s review more details about HDG steel.

Galvanized Coil Production

Galvanized Coil Production

GI Coil

GI Coil

What Is Hot Dip Galvanizing Steel?

As mentioned, hot dip galvanizing is a form of galvanization. Galvanizing is a process where zinc coating is applied to the base metal to prevent the steel from corroding. While hot dip galvanizing only refers to a zinc coating formed by immersing the metal into zinc molten at a temperature of about 450 °C. Compared to the electro galvanizing layer (10-50 g/m2), hot-dip galvanized zinc layer will be much thicker, which can reach up to 600 g/m2. And the tough protective zinc coating provides superior corrosion resistance. That’s why HDG steel is very popular in many applications.

Applications of Hot Dipped Galvanized Steel

Hot dipped galvanized steel (HDG) is ideal for the applications, such as roofing, wall panels, framing, siding, structural steel beams, pipes, railing, etc. It is popular in the fields such as construction, home appliances, automobiles, containers, and transportation. Especially, you can find it in steel structure construction, automobile manufacturing, steel silo manufacturing and other industries. Also, the zinc coating also makes the metal sheet smooth and shiny. So it is also widely used as the back panel of the indoor unit of the air conditioner, cabinet, etc. If another color is desired, it is easily painted.

Production Process of HDG Steel

The production process of HDG steel is as follows: Uncoiling → degreasing →  pickling → water washing →  flux solvent → drying → galvanizing → cooling → quality inspection → packaging.

Hot-dip Galvanizing Process

Hot-dip Galvanizing Process

1. Clean the grease, dirt, and paint on the surface of steel coil. The coils need to be uncoiled and welded for continuous processing.
2. Rinse off the cleaning solution.
3. Put into an acidic solution to remove mill scale.
4. Wash off the pickling solution.
5. Dip the steel into the molten zinc bath for galvanizing.
6. Cool down and roll up the steel into coils for sale.

Advantages of Hot Dipped Galvanized Steel

1. Strong Resistance to Corrosion

Through hot dip galvanizing process, the base metal will be coated with a thick zinc protective coating. The thick zinc layer offers a strong antioxidant ability to prevent the steel coil from rusting and prolong its service life.

2. Comprehensive Protection

The entire steel surface is uniformly covered with a zinc layer, even the corners, hollows, etc. so that the steel coil is fully protected. That’s why the hot galvanized steel is more durable.

3. Decorative Performance

After galvanizing, the steel coil looks bright and shiny so that it can be used directly without decoration.

4. Good Processing Formability

HDG steel is easy to process for different uses. That’s why galvanized steel coil is a great choice for investment.

HDG Coils at Factory

HDG Coils at Factory

Hot-dipped GI Sheets

Hot-dipped GI Sheets

Difference Between Hot-Dip and Electro-galvanized Steel

1. Thickness of Zinc Layer

Generally, the thickness of the electro-galvanizing layer is 5~15 μm, but the hot galvanizing layer is often more than 35 μm, or even as high as 275 μm.

2. Resistance to Corrosion

The corrosion resistance of hot-dip galvanized steel coil is much better than that of an electro-galvanized one.

3. Appearance

The appearance of the electro-galvanized iron coil is smoother and brighter, while the surface of hot-dip galvanized iron coil is rough and dull.

Hot Dipped Galvanized VS Electro-galvanized Steel

Appearance Difference

4. Application Environment

Hot-dip galvanizing products are applicable for outdoor environments, such as transportation, building, electric power, energy, automobile, petrochemical, home appliances, and other industries. But the electro-galvanized steel coil is more suitable for small parts, or indoor environments, etc.

5. Cost

Due to the electro-galvanizing process being easier and the zinc coating being thinner, its price is also much cheaper. While the hot-dip one is more expensive but durable to use.


Hot dipped galvanized steel has good weldability and formability so that it is usable for many applications. Also, the thick zinc coating offers superior corrosion resistance so that it is long-lasting to use. Besides, it also has a smooth and shiny surface. But it is more affordable than color-coated steel. That’s why hot dipped galvanized products are very popular. At Wanzhi Steel, we have 3 continuous galvanizing lines and other equipment. Except for galvanized coils, we also manufacture corrugated sheets, plain sheets, and GI strips to meet different needs. The annual output is about 540,000 tons. If you want to know more information, please feel free to contact us!

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