Electro Galvanized Steel Sheet & Coil

Electro-galvanized steel is a type of steel that has been coated with a layer of zinc for protection through an electroplating process. Using cold-rolled steel sheet as a substrate, zinc ions are reduced in a zinc salt solution through electrochemical principles and continuously deposited onto the surface of the steel strip, forming a uniform, dense, and well-bonded zinc or zinc-nickel alloy coating. Therefore, electro-galvanized steel is also known as cold-galvanized steel.
Product forms include steel sheet (supplied in flat form) and steel strip (supplied in coil).

The core value of electro-galvanized steel coils lies in the ultimate balance between coating uniformity, surface quality, and processing performance. Unlike hot-dip galvanizing, electro-galvanizing precisely controls coating deposition through the action of an electric field, resulting in an extremely thin and uniform zinc layer while fully preserving the excellent surface quality and stamping performance of the cold-rolled substrate.
Electro-galvanized steel coils are considered a high-end product in the sheet metal industry, with more advanced applications than ordinary hot-dip galvanized steel coils, but their application range and usage volume are far less than those of hot-dip galvanized steel coils.

Electroplating Zinc Process: Electroplating is a process of electroplating a layer of zinc onto the surface of steel. This is accomplished by passing an electric current through a solution of zinc and brine, along with the zinc anode and the steel conductor. The purpose of electroplating is to protect steel from corrosion, extend its service life, and enhance its decorative appearance. Zinc has high oxidation resistance in both dry air and humid environments, preventing corrosion. When the protective layer is damaged, micro-cells form between the zinc and the steel, ensuring the steel substrate is protected.
The full cold galvanizing process is as follows: Chemical degreasing → Hot water cleaning → Water washing → Electrolytic degreasing → Water washing → Pickling → Rust removal → Water washing → Electroplating → Water washing → Passivation → Hot water cleaning → Drying → Quality inspection → Packaging and sale

Core Performance Characteristics:
1. Excellent Surface Quality: The most prominent advantage of electroplated galvanized steel coils is their excellent surface quality. The electroplated zinc layer is uniform, dense, and well-bonded, resulting in a high surface finish. Surface quality is classified into three grades: FB, FC, and FD, with FD grade meeting the highest surface requirements. Its surface quality is superior to that of hot-dip galvanized steel.
2. Uniform Coating and Controllable Thickness: Electro-galvanizing precisely controls coating deposition through electrochemical methods, resulting in an extremely thin and highly uniform zinc layer. The minimum single-sided coating weight is 3g/m², and the maximum is approximately 110g/m². The coating uniformity is far superior to hot-dip galvanizing.
3. Excellent Processing and Forming Performance: Electro-galvanized sheet coils retain the excellent stamping performance of the cold-rolled substrate. The coating adhesion is good; no coating peeling should occur during bending tests (bending mandrel diameter 0a, bending angle 180°). In the mechanical properties of zinc-nickel alloy coated products, the elongation after fracture is allowed to decrease by 2 units compared to the substrate, and the r-value is allowed to decrease by 0.2.

4. Good Corrosion Resistance: The electro-galvanized layer adheres tightly to the steel plate surface, forming a protective barrier that effectively isolates the steel plate from corrosive substances such as moisture and salt in the external environment. The coating thickness is uniform and dense, resisting corrosion from most acidic and alkaline environments and atmospheric pollutants. Chromium-free, fingerprint-resistant, and other environmentally friendly surface treatments further enhance corrosion resistance. 5. Excellent Coating and Conductivity: Electro-galvanized steel coils can undergo various surface treatments such as chromate passivation, phosphate treatment, and fingerprint-resistant treatment. By selecting different surface treatment schemes, multiple functions such as fingerprint resistance, high conductivity, high corrosion resistance, and high heat dissipation can be achieved.
6. Main Limitations:
Thinner Coating: The coating weight is much less than that of hot-dip galvanized steel (hot-dip galvanizing has a minimum double-sided weight of 50-60 g/m², and a maximum of 600 g/m²).
Unsuitable for Outdoor Use: Due to the relatively small coating weight, it is not suitable for outdoor exposure without surface chemical treatment and painting.
Higher Cost: The process is complex, and the production cost is higher than that of hot-dip galvanized steel.

The difference between electro-galvanized steel coils and hot-dip galvanized steel coils

Electro-galvanized steel coils are characterized by excellent surface quality, uniform coating, and superior processing performance, and are mainly used in high-end fields such as automobile manufacturing, home appliances, and electronics. Compared with hot-dip galvanized steel coils, electro-galvanized steel coils have a thinner coating, better surface quality, and superior processing performance, but they have weaker corrosion resistance, higher cost, and are not suitable for outdoor exposure. Currently, electro-galvanized steel coils are continuously developing towards high-end products, environmentally friendly surface treatments, and focused applications.

In China, the standards for Electro Galvanized Steel Sheet & Coil are set and regulated by the Chinese National Standards (GB/T) issued by the Standardization Administration of China (SAC). The relevant GB/T standard for Electro Galvanized Steel is:

GB/T 17675: Electrolytic zinc-coated steel sheets and coils.

GB/T 17675 specifies the requirements for electrolytic zinc-coated steel sheets and coils, which includes Electro Galvanized Steel. The standard covers the thickness, weight of the zinc coating, and other mechanical and surface properties of the electro galvanized steel.

This GB/T standard ensures that Electro Galvanized Steel Sheet & Coil products produced and used in China meet the necessary quality and safety requirements for their intended applications.

In the United States, the standards for Electro Galvanized Steel Sheet & Coil are set and maintained by the American Society for Testing and Materials (ASTM). The most commonly referenced ASTM standard for Electro Galvanized Steel is:

ASTM A879/A879M: Standard Specification for Steel Sheet, Zinc Coated by the Electrolytic Process for Applications Requiring Designation of the Coating Mass on Each Surface.

ASTM A879/A879M covers the requirements for steel sheet products coated with zinc by the electrolytic process. The standard specifies the thickness of the zinc coating, the surface finish, and other properties of the electro galvanized steel.

This standard is used to ensure the quality and performance of electro galvanized steel products and provides valuable information for manufacturers, suppliers, and end-users in the US market.

In the United Kingdom, the standards for Electro Galvanized Steel Sheet & Coil are generally aligned with the European standards set by the European Committee for Standardization (CEN). The most relevant European standard for Electro Galvanized Steel is:

EN 10152: Electrolytically zinc coated cold rolled steel flat products for cold forming - Technical delivery conditions.

EN 10152 specifies the requirements for electrolytically zinc-coated cold-rolled steel flat products for cold forming. This standard covers the thickness, tolerances, and mechanical properties of the electro galvanized steel, as well as the characteristics of the zinc coating.

EN 10152 is used as the basis for product certification and quality assurance in the European market and ensures that electro galvanized steel products meet the necessary requirements for their intended applications.

In addition to EN 10152, other European standards may also be relevant, depending on specific applications or industries. These standards are often harmonized across the European Union to facilitate trade and ensure consistent product quality.

In Japan, the standards for Electro Galvanized Steel Sheet & Coil are set and regulated by the Japanese Industrial Standards (JIS). The relevant JIS standard for Electro Galvanized Steel is:

JIS G 3313: Electrolytic Zinc-coated Steel Sheets and Coils.

JIS G 3313 specifies the requirements for electrolytic zinc-coated steel sheets and coils, which includes Electro Galvanized Steel. The standard covers the thickness, weight of the zinc coating, and other mechanical and surface properties of the electro galvanized steel.

This JIS standard ensures that Electro Galvanized Steel Sheet & Coil products produced and used in Japan meet the necessary quality and safety requirements for their intended applications.

Grade system of electro-galvanized steel coils

Baosteel's Enterprise Standard Grade System

Baosteel offers a wide range of electroplated zinc products, covering various substrate types.

Coating weight range:
The coating weight of electro-galvanized sheet coils is much less than that of hot-dip galvanized sheets.

The permissible dimensional deviations of electro-galvanized sheet coils shall conform to the provisions of GB/T 708 (width ≥ 600 mm) and GB/T 15391 (width < 600 mm) respectively, based on the width.

Thickness tolerances are shown in the example below.

Hot rolled raw plate unit: mm