How Is Galvanized Steel Made?

Galvanized steel is made by applying a layer of zinc to the surface of steel or iron to protect it from rust and corrosion. Meanwhile, the smooth and fine zinc coating also offers decorative purposes.

There are two main galvanizing processes, hot-dip galvanizing and electro-galvanizing. This article will focus on the production processes of these two galvanized steels.

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Galvanizing Method

1. Hot-dipped Galvanizing (HDG) Process

Hot-dip galvanizing is the process of immersing the steel or iron in the molten zinc at about 480 ℃ to apply a zinc layer on the surface. Here is the process: Uncoiling & welding — Degreasing & cleaning — Annealing & Pickling — Drying — Galvanizing — Cooling  — Inspection.

At Wanzhi Steel, we often use cold-rolled or hot-rolled coils as the base metal.

1) The base metal is uncoiled and welded first.

2) The next step is the pre-treatment process, including degreasing, washing, and drying.

3) Then the steel coil is heated to 700-800 degrees for recrystallization annealing. After that, cool down the metal to 480 ℃.

4) Finally, it is immersed in a zinc pot under sealed conditions. After cooling and quality inspection, the galvanized steel will be rolled up for sale.

The hot-dip galvanizing process offers a thick and dense pure zinc layer to protect the base metal from corrosion.

2. Electro-galvanizing Process (EG)

Electro galvanizing, also called cold galvanizing, forms a zinc layer on steel or iron surfaces through electrolysis. It uses an electrochemical method: zinc ingots (as anodes) lose electrons to become ions and dissolve into the electrolyte, while steel (as the cathode) allows zinc ions to gain electrons, turn into zinc atoms, and deposit on its surface to form a zinc coating. Before electroplating, grease and oxides on the base metal must be removed to ensure coating adhesion. Below is its specific process:

Degreasing (at 5 -40°C) — Washing with water (at room temperature) —  rust cleaning — Washing with water (at room temperature) — Electro galvanizing  (5-60°C) — Washing with water (at room temperature) — Passivating — Washing with hot water (≤70°C) — Drying — Cooling — Quality Inspection.

Conclusion

1. Process
Electrogalvanizing is performed through an electrode reaction, while hot-dip galvanizing involves immersing the raw material in a zinc bath. This involves a physical reaction and an intermetallic reaction. Therefore, the surface of hot-dip galvanized steel sheet not only has a layer of intermetallic compounds but also a zinc layer.
2. Zinc Layer
The zinc layer of electrogalvanized steel sheet is thinner (≤30 g/m²), while the zinc layer of hot-dip galvanized steel sheet is thicker, generally ranging from 30 to 600 g/m². Therefore, hot-dip galvanized steel sheet has better corrosion resistance than electrogalvanized steel sheet.
3. Surface Finish
The surface of hot-dip galvanized steel sheet is smoother than that of electrogalvanized steel sheet. Wanzhi Steel Company’s highest zinc layer thickness is 275 g/m² (Z275 or G90).
4. Applications
Electrogalvanized steel sheet is suitable for small components such as screws, wire, and locks, while hot-dip galvanized steel sheet is suitable for larger components and is widely used in the construction, chemical, petroleum, municipal, agricultural, and railway sectors.

Choosing the Right Galvanized Steel for Your Project

Selection of zinc layer thickness

he thickness of the zinc layer directly affects the corrosion resistance and appearance quality of galvanized steel.Too thin a coating has insufficient anti-corrosion performance, while too thick a coating may affect the appearance and increase costs.Therefore, when choosing the thickness of the zinc layer, you should consider your budget and application scenarios.

Process selection

Choose a suitable galvanizing process according to the specific needs and uses of the product.For example, hot-dip galvanizing is a better choice for large components and thick plates, while electrogalvanizing is more suitable for thin plates and small parts.

Choose a reliable manufacturer

When choosing a manufacturer, it is necessary to review it, including qualifications, reputation, quality certification, etc.

• We are an ISO 9001:2015 certified factory.
• Our galvanized steel products are exported to more than 120 countries and regions, and our customers are very satisfied with our products.

Galvanized Steel Coil/Sheet Supplier – Wanzhi Steel

Wanzhi Steel has two hot-dip galvanizing production lines and one electro-galvanizing production line, as well as multiple slitting, cutting, profiling, and other equipment. Therefore, the galvanized products we can provide include galvanized steel coils, galvanized steel sheets, galvanized steel strips, galvanized corrugated sheets, etc. Full specifications and models to meet the needs of various projects.

As the most professional galvanized steel manufacturer in China, we can provide you with the most competitive wholesale prices while ensuring product quality. If you have any needs, you are welcome to contact us at any time.

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