Galvanized steel and stainless steel are two common metal materials, so what is the difference between these two materials? How should we choose? This article will compare the two materials, hoping to help you better understand them.
What Is Galvanized Steel?
Galvanized steel is a steel with a layer of zinc on the surface of ordinary carbon steel or low-alloy steel. Ordinary steel is prone to oxidation and rust in a humid environment, while the zinc coating can effectively isolate air and moisture, forming a protective barrier to prevent steel corrosion. According to the different galvanizing processes, galvanized steel is mainly divided into hot-dip galvanized steel (Hot-Dip Galvanized Steel) and electro-galvanized steel (Electro-Galvanized Steel).
- Hot-dip galvanizing: Hot-dip galvanizing is to immerse the steel in high-temperature molten zinc liquid so that the zinc is evenly attached to the surface to form a firm coating. This method of coating is thicker and more corrosion-resistant.
- Electrogalvanizing: Electrogalvanizing uses electrochemical principles to deposit a thin but uniform layer of zinc on the surface of steel. The coating of this method is thinner and has a smooth and beautiful appearance. It is suitable for products with high surface quality requirements but low corrosion resistance requirements, such as home appliance housings, screws, hardware accessories, etc.
Role Of The Zinc Layer:
The zinc layer not only provides physical barrier protection, but also forms a zinc oxide or zinc carbonate layer on the surface of the steel, further enhancing the corrosion resistance.
Classification Of Galvanized Steel:
Different types of galvanized steel products vary according to the coating thickness, processing method and application requirements, and can be divided into galvanized sheets, galvanized coils, galvanized profiles, etc.
What Is Stainless Steel?
Stainless steel is a steel containing alloy elements such as chromium (Cr) and nickel (Ni), which can resist oxidation and corrosion in air or humid environments.
The Role Of Elements:
The main components of stainless steel include iron (Fe), chromium (Cr), nickel (Ni) and other alloy elements. These main components all play an important role. Chromium is the most critical element, with a content usually above 10.5%. It can form a dense chromium oxide film on the surface of the steel, giving it self-repairing ability. Even after the surface is slightly damaged, the protective layer can be quickly restored to improve corrosion resistance. In addition, the addition of nickel can enhance the strength, toughness and corrosion resistance of steel, while elements such as molybdenum (Mo) further enhance its corrosion resistance in harsh environments such as acidic and marine environments.
Classification Of Stainless Steel:
According to the different metallographic structures, stainless steel can be divided into austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, duplex stainless steel, etc.
- Austenitic stainless steel (Austenitic Stainless Steel): Typical grades include 304, 316, etc., with good corrosion resistance and plasticity, widely used in food processing, medical equipment, chemical equipment and other fields.
- Ferritic stainless steel (Ferritic Stainless Steel): such as 430 stainless steel, mainly composed of iron and chromium, with good corrosion resistance, but low toughness, often used in automobile exhaust pipes, washing machines, etc.
- Martensitic stainless steel (Martensitic Stainless Steel): such as 410, 420 stainless steel, with high hardness, can be used in knives, valves and other fields.
- Duplex Stainless Steel: Combining the advantages of austenite and ferrite, it has high strength and excellent corrosion resistance, and is suitable for marine engineering and chemical equipment.
Surface Treatment Of Stainless Steel:
Stainless steel can meet various decorative and functional requirements after different surface treatment processes (such as brushing, mirror polishing, sandblasting, etc.)
Zinc Plated Steel Vs. Stainless Steel
1. Corrosion Resistance:
The corrosion resistance of galvanized steel mainly depends on the protective effect of the zinc layer, which can form a dense oxide barrier to prevent corrosion inside the steel. However, if the galvanized layer is damaged, the base steel is prone to rust.
The corrosion resistance of stainless steel comes from the protection of the chromium oxide layer, which can repair itself in air or humid environments even if the surface is damaged. This makes stainless steel far more corrosion-resistant than galvanized steel, especially in high humidity, acidic or marine environments, stainless steel is more durable.
2. Mechanical Properties
Galvanized steel usually uses low-carbon steel as the base material, so it has good ductility and toughness, and can be processed by stamping, bending, welding and other processing operations. However, the galvanized layer is brittle and easily peels off under strong impact or friction.
Stainless steel has high strength and hardness, especially austenitic stainless steel has excellent ductility and impact resistance.
3. Appearance and surface treatment
The surface of galvanized steel is silvery white or grayish white with a certain luster. The thickness and uniformity of its coating depend on the galvanizing process. For example, hot-dip galvanizing usually has a rough surface, while electroplating is smoother.
Stainless steel has a higher surface finish and can present a variety of appearance effects after different surface treatments (such as brushing, mirror, sandblasting, etc.). In contrast, stainless steel is more decorative and more suitable for high-end products.
4. Price and cost
The cost of galvanized steel is low, mainly because the substrate is ordinary steel, and the addition of zinc layer does not significantly increase the production cost. Therefore, it is widely used in cost-sensitive industries such as construction and automobiles.
The cost of stainless steel is high because of its high content of alloy elements, complex production process and high processing difficulty. Taking 304 stainless steel as an example, its price is much higher than galvanized steel, but due to its greater durability, the long-term use cost may be more advantageous.
5. Application fields
Galvanized steel is widely used in the following fields:
- Construction industry (roofs, walls, doors and windows)
- Home appliance industry (refrigerator, washing machine shell)
- Automobile manufacturing (body, chassis)
- Pipeline system (water supply pipes, ventilation pipes)
Stainless steel is widely used in the following fields:
- Medical industry (surgical instruments, medical equipment)
- Food processing (tableware, food storage tanks)
- Chemical industry (equipment in corrosive environments)
- Shipbuilding (marine environment structural parts)
How To Choose?
Galvanized sheet and stainless steel are both common metal materials. They differ in chemical composition, corrosion resistance, color and appearance, hardness and strength, price and application scenarios. The selection of suitable materials should be based on specific needs and application scenarios to ensure that the product has good performance and service life.
