What is Gray Electrolytic Steel Material?

"Gray electrolytic" is a very descriptive colloquial term used in the steel industry to refer to alloyed hot-dip galvanized steel sheets (GA sheets). While not an official academic term, it accurately summarizes the key technological characteristics and appearance of this product.

Origin of the term "Gray Electrolytic"

The colloquial term "Gray electrolytic" combines the product's appearance and core process:

1. "Gray" refers to the appearance color:

Alloyed hot-dip galvanized steel sheets have a uniform dark gray or matte grayish-white surface. This differs from the bright white and obvious zinc bloom appearance of ordinary hot-dip galvanized sheets (pure zinc coating). This gray color comes from the fact that its coating is primarily a zinc-iron alloy, with an iron content typically between 8% and 15%.

2. "Electrolysis" originates from a key process step:

Here, "electrolysis" does not refer to the electrolytic process used to prepare zinc oxide or electroplated zinc sheets (electrolytic plates), but rather to a crucial processing step in the production of alloyed hot-dip galvanized sheets—alloying heat treatment. Ordinary hot-dip galvanized sheets primarily have a pure zinc coating. To obtain a zinc-iron alloy coating, hot-dip galvanized steel strip undergoes an alloying heat treatment process (e.g., annealing in an alloying furnace). During this process, the zinc in the coating diffuses with the iron in the steel substrate at high temperatures, forming a uniform and dense zinc-iron alloy layer.

Therefore, "gray electrolysis" vividly describes the steel sheet with a gray zinc-iron alloy coating ("gray") obtained through alloying heat treatment ("electrolysis").

Key characteristics of "gray electrolysis" steel sheets: Compared to traditional pure zinc-coated hot-dip galvanized sheets, "gray electrolysis" steel sheets have the following outstanding characteristics:

Superior coating performance: This is its core advantage. The gray zinc-iron alloy layer has a rougher and more porous surface, resulting in excellent adhesion to paints and coatings, making it an ideal substrate for subsequent electrophoretic coating, spraying, and other coating processes.

Higher corrosion resistance: The chemical stability of the zinc-iron alloy layer is higher than that of pure zinc. After passivation treatment, its corrosion resistance, especially its resistance to red rust, is typically 2 to 3 times higher than that of a pure zinc coating of the same weight.

Excellent weldability: The iron content in the coating results in higher resistance, more stable current during welding, and less spatter.

Weldability is generally superior to ordinary hot-dip galvanized coils.

Uniform surface without zinc spangles: Alloying treatment eliminates zinc spangles, resulting in a uniform and delicate surface, making it more suitable for high-quality finished parts.

Distinguishing between "Gray Electrolytic" and Ordinary "Electrolytic Plate"

It is important not to confuse "Gray Electrolytic" with ordinary "electrolytic plate" (i.e., electro-galvanized plate):

"Gray Electrolytic" (Alloyed Hot-Dip Galvanized Plate, GA): The substrate is first hot-dip galvanized, then undergoes alloying heat treatment; the coating is a zinc-iron alloy.

Ordinary "Electrolytic Plate" (Electro-galvanized Plate, EG): A layer of pure zinc is directly plated onto the substrate using electrolysis; the coating is primarily pure zinc.

The processes and coating structures of the two are fundamentally different; the term "Gray Electrolytic" is more of an industry-specific descriptive term.

Main Application Areas

Thanks to its superior coating performance and corrosion resistance, "gray electrolytic" steel sheets are primarily used in fields with high requirements for surface quality and corrosion resistance:

* Automotive Industry: Widely used for interior and exterior body panels of automobiles, such as doors and hoods.

* High-end Home Appliances: Visible exterior components of appliances such as refrigerators, washing machines, and microwave ovens.

* Other fields requiring high-quality coating.

Summary

The common name "gray electrolytic" is a precise summary of the process and appearance characteristics of alloyed hot-dip galvanized steel sheets (GA) by steel industry professionals. Understanding the "gray" (the appearance of the zinc-iron alloy coating) and the core alloying heat treatment process indicated by "electrolysis" allows one to grasp the essence of this type of product.