Your Professional Galvanized Steel Supplier
Henry Steel was founded in 1995 and has been focusing on steel supply and services for over 30 years, accumulating extensive experience and stable supply capabilities. The company’s headquarters is located in Jinan, one of China’s largest steel raw material bases, adjacent to high-speed rail stations and airports, and bordering Tianjin Port to the north and Qingdao Port to the east, offering a superior geographical location with efficient and convenient logistics.
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Galvanized Steel
Galvanized steel is a steel alloy that has been coated in zinc to protect the underlying metal from corrosive elements. There are many ways to galvanize steel, including:
Hot-dip galvanizing (hot-dipped galvanized or HDG):
Steel coil is run through a bath of molten 99.5% pure zinc. The most common method for galvanization occurs on continuous galvanizing lines, where coils are welded together end-to-end and run through a bath of molten zinc. In industry parlance, regular HDG is referred to as “GI.”
Galvannealed:
Produced on the same lines as GI, galvannealed is created by reheating the coil strip above the air knives to bond or alloy the zinc to the steel substrate. Most people know that galvannealed has a coating that is about 10% iron. However, iron is not added to the zinc bath. Instead, some of the aluminum content in the zinc bath is reduced and the iron reacts with the zinc in the reheating process to form an iron-zinc alloy. In industry parlance, galvannealed is abbreviated as “GA”.
Electrogalvanizing:
A process quite different from hot-dip galvanizing, the zinc coating is applied to the steel in an electroplating process, where the anode is zinc, the cathode is steel, and the electrolyte is zinc sulfate. In other words, electrically applied rather than dipped in zinc. This process consumes a lot of electricity but leaves an excellent finish. Its main application has been in the automotive industry. In industry parlance, electrogalvanized steel is referred to as “EG.”
Galvanized Steel Advantages
Since its sacrificial zinc layer protects from many different types of environmental conditions, galvanized steel offers many unique benefits, these include:
Rust Resistance: Iron in steel is incredibly prone to rust, but zinc acts as a protective buffer between moisture, oxygen, and steel.
Easy Inspection: It’s fairly simple to tell how strong a galvanized coating is, just by looking at it. Quick stress tests that can tell you how thick the zinc is.
Sacrificial Anode: This ensures that any damaged steel is protected by the surrounding zinc coating. It doesn’t matter if the steel section is completely exposed; the zinc will still corrode first.
Longer Life: With galvanization, a piece of industrial steel is expected to last more than 50 years in average environments and can last over 20 years with severe water exposure. No maintenance required.
Physical Properties of Galvanized Steel
|
Property |
Characteristic |
|
Tensile strength |
510–600 MPa |
|
Density |
7.8 g/cc |
|
Hardness (Rockwell B) |
74 |
|
Young’s modulus |
210 GPa |
Chemical Properties of Galvanized Steel
|
Property |
Description |
|
Reactivity |
Low |
|
Toxicity |
Non-Toxic |
|
Flammability |
Non-Flammable |
|
Melting Point |
1200 °C |
The Process to make Galvannealed Steel
Surface Preparation: Similar to galvanized steel, the surface preparation of the steel is crucial. It involves thorough cleaning to remove dirt, rust, and contaminants. The steel may undergo a degreasing process or chemical cleaning to ensure a clean surface for proper coating adhesion.
Acid Pickling: After the initial cleaning, the steel is subjected to acid pickling. This step involves immersing the steel in an acid solution, typically a mixture of hydrochloric acid and sulfuric acid. Acid pickling removes any remaining mill scale, rust, or oxides from the steel surface, leaving it clean and prepared for the subsequent processes.
Fluxing: Once the steel has been pickled, it goes through fluxing, similar to the galvanization process. Flux, a chemical compound containing zinc ammonium chloride and other additives, is applied to the steel’s surface. Fluxing removes any remaining oxides, promotes the flow of the zinc coating, and prepares the surface for galvanization.
Galvanization: The galvanization step is similar to the process used for galvanized steel. The steel is immersed in a bath of molten zinc, heated to a temperature between 815°C and 850°C (1500°F and 1560°F). As the steel is submerged, the molten zinc reacts with the iron in the steel, forming a zinc coating.
Heat Treatment (Annealing): After galvanization, the steel is further processed through a heat treatment known as annealing. The galvanized steel is heated to a specific temperature, typically around 550°C to 600°C (1020°F to 1110°F), and held at that temperature for a predetermined time. This heat treatment allows the zinc coating to alloy with the steel, creating a zinc-iron alloy layer.
Cooling: After the annealing process, the galvannealed steel is slowly cooled. The controlled cooling process helps in solidifying the zinc-iron alloy layer, ensuring its adhesion to the steel surface.
Inspection and Quality Control: Once the galvannealing process is complete, the galvannealed steel undergoes a rigorous inspection and quality control. The steel is examined for any imperfections, such as uneven alloying, surface defects, or insufficient coating thickness. Various tests, including visual inspection, coating thickness measurement, and adherence to applicable standards, are performed to ensure the final product meets the required specifications.
Regarding galvanized steel, proper handling, and storage are crucial to maintaining its quality and effectiveness. Here are some guidelines to follow:
Handling
Handle with care: Galvanized steel is coated with a protective layer of zinc, which can be scratched or damaged if mishandled. Avoid dropping, dragging, or sliding galvanized steel to prevent any potential damage to the coating.
Storage
Store in a dry, well-ventilated environment. Moisture can accelerate corrosion on galvanized steel, resulting in white rust caused by zinc oxidization. Before fabricating, storing galvanized steel in a dry environment is essential to minimize exposure to moisture or humidity. Regardless, a well-ventilated storage area with low humidity levels is ideal for long-term storage—ceiling fans are an excellent solution to prevent white rust from occurring.
FAQ
We're known as one of the most professional galvanized steel manufacturers and suppliers in China. Please rest assured to buy high quality galvanized steel for sale here from our factory. For price consultation, contact us.
