In daily life, we often come into contact with various metal products. From kitchen sinks and knives to scaffolding and steel beams on construction sites, galvanized steel and stainless steel are everywhere, quietly serving our daily life and production needs.
In this article, we will compare galvanized steel and stainless steel from multiple perspectives, so you can better understand their advantages and disadvantages.
What is Galvanized Steel?
Galvanized steel refers to steel that has a layer of zinc applied to its surface through processes like hot-dip galvanizing or electro-galvanizing. The zinc layer helps prevent rust and corrosion, extending the lifespan of the steel.
There are two main types of galvanized steel:
Pre-formed Galvanizing
This method involves galvanizing steel before it is shaped into its final form, such as when it is still in the form of sheets, coils, or bars. Common galvanizing processes include hot-dip galvanizing (dipping steel into molten zinc) and electro-galvanizing (using electricity to deposit zinc onto the steel).
Pre-formed galvanizing can process large amounts of steel continuously, making it suitable for industrial-scale production. It creates a uniform, dense zinc layer that offers good corrosion resistance.
Post-formed Galvanizing
This method involves shaping the steel into the final product, such as structural parts, pipes, or bolts, and then applying the zinc coating. Hot-dip or electro-galvanizing can be used, but special care is taken to ensure the zinc coating reaches all areas of the product.
Post-formed galvanizing is suitable for complex-shaped products and ensures that any small damage to the surface during forming can be repaired later, maintaining corrosion resistance.
As a casting factory, we perform galvanizing on carbon steel castings after they are cast. Similarly, we also apply galvanizing to steel after machining, according to customer requirements.
What is Stainless Steel?
Stainless steel is an alloy steel known for its excellent corrosion resistance. By adding chromium (≥10.5%), it forms a chromium oxide layer on the surface that prevents internal rust. Nickel, molybdenum, and other elements are often added to improve performance. It has a shiny appearance, is easy to clean, and is highly resistant to corrosion.
Common types of stainless steel include austenitic, ferritic, and martensitic stainless steels.
Do Galvanized Steel and Stainless Steel Rust?
Galvanized steel has a zinc layer on top of regular steel to prevent rust. The zinc layer forms a dense protective oxide film in the air, blocking oxygen and moisture from reaching the steel. However, in harsh corrosive environments, such as strong acids or bases, the zinc layer may be worn away, and the steel underneath may begin to rust.
Stainless steel contains chromium, nickel, and other alloy elements. Chromium forms a stable passive film on the surface, which can even self-repair if slightly scratched. Therefore, stainless steel has excellent corrosion resistance in most environments, especially in harsh conditions, where its performance is far superior to galvanized steel.
Is Stainless Steel Stronger Than Galvanized Steel?
The strength and hardness of galvanized steel mainly depend on the carbon content of the steel and its heat treatment. The galvanizing process does not significantly affect the steel’s strength. In general, galvanized steel is strong enough to withstand most mechanical loads.
The strength of stainless steel varies by type. Some austenitic stainless steels have high toughness and good strength, while martensitic stainless steels have higher hardness and strength. Overall, in the same conditions and specifications, some stainless steels may be stronger and harder than galvanized steel, but others may be similar in strength.
Is Galvanized Steel Easier to Process Than Stainless Steel?
Galvanized steel has moderate strength and hardness, and when machining, it causes relatively less tool wear. The surface quality is also generally good. However, the zinc layer may cause tool wear, and its shedding during cutting can affect machining accuracy and surface roughness. To avoid this, galvanized steel is often processed after machining.
Stainless steel, compared to galvanized steel, is harder to machine. Stainless steel is tougher, has high strength, and the cutting force is larger. Additionally, the chips produced are hard to break and can get stuck on the tool, reducing efficiency and surface quality. To improve machining, high-performance tools such as carbide tools are needed, and cutting parameters should be optimized (e.g., reducing cutting speed and increasing feed rate).
Casting Properties of Galvanized Steel and Stainless Steel
Galvanized steel castings are usually created by first casting carbon steel and then applying a zinc coating. Carbon steel has good casting fluidity, filling molds well in the molten state, and is suitable for making complex-shaped castings. It also has a stable shrinkage rate, ensuring dimensional accuracy.
Stainless steel casting is more complicated. Some austenitic stainless steels have poor fluidity, which can cause problems like incomplete mold filling or cold shuts. Stainless steel also has a larger thermal expansion coefficient, so it may develop internal stresses during cooling, leading to warping or cracking of castings. As a result, galvanized steel is easier to produce for castings than stainless steel.
Is Galvanized Steel Heavier Than Stainless Steel?
Generally, stainless steel has a density of about 7.93g/cm³, while regular carbon steel has a density of about 7.85g/cm³. So, stainless steel may be slightly heavier than galvanized steel for the same volume, but the difference is small. If the zinc coating on galvanized steel is thick, it can also add to its weight.
Ductility of Galvanized Steel and Stainless Steel
The ductility of galvanized steel depends on the properties of the base steel. Regular carbon steel usually has good ductility and can be bent or stretched. However, if the zinc coating is too thick or applied improperly, it may slightly reduce its ductility.
Austenitic stainless steel has excellent ductility and can undergo complex processes like deep drawing or bending without cracking. Ferritic stainless steel has poorer ductility, and martensitic stainless steel is also less ductile than austenitic stainless steel. Therefore, if stainless steel must be chosen, it is recommended to use austenitic stainless steel.
Thermal Conductivity of Galvanized Steel and Stainless Steel
The thermal conductivity of galvanized steel mainly depends on the type of steel. Regular carbon steel has good thermal conductivity, with a thermal conductivity coefficient of about 45W/(m·K). The zinc layer has some effect on thermal conductivity, but since it is thin, the impact is small.
Stainless steel has lower thermal conductivity. For example, austenitic stainless steel has a thermal conductivity coefficient of about 15W/(m·K), much lower than regular carbon steel, because the alloy elements in stainless steel hinder heat flow.
Which is Better for Welding: Galvanized Steel or Stainless Steel?
When welding galvanized steel, the zinc layer evaporates at high temperatures, which can create zinc vapor and cause defects like porosity and cracks in the weld. Therefore, special techniques, such as removing the zinc layer and using proper welding materials and processes, are needed for welding galvanized steel. We recommend applying galvanizing after welding steel.
Stainless steel’s weldability varies by type. Austenitic stainless steel has good weldability, but ferritic and martensitic stainless steels are prone to problems like heat-affected zone brittleness during welding, requiring preheating and post-weld heat treatment.
Do Galvanized Steel and Stainless Steel Have Magnetic Properties?
Ordinary steel is magnetic. The galvanizing process doesn’t affect its magnetic properties, so galvanized steel is usually magnetic.
Stainless steel’s magnetism depends on the type. Austenitic stainless steel is usually non-magnetic, but it can show weak magnetism if cold-worked. Ferritic and martensitic stainless steels are magnetic.
Do Galvanized Steel and Stainless Steel Have Magnetic Properties?
Ordinary steel is magnetic. The galvanizing process doesn’t affect its magnetic properties, so galvanized steel is usually magnetic.
Stainless steel’s magnetism depends on the type. Austenitic stainless steel is usually non-magnetic, but it can show weak magnetism if cold-worked. Ferritic and martensitic stainless steels are magnetic.
Is Stainless Steel More Expensive Than Galvanized Steel?
Galvanized steel is relatively cheap because the base steel is inexpensive and the galvanizing process is simple. This makes galvanized steel a good choice for cost-sensitive projects.
Stainless steel contains expensive alloy elements like chromium and nickel, which increase its cost. Additionally, the production process for stainless steel is more complex, further raising the price. Therefore, stainless steel is usually more expensive than galvanized steel.
Applications of Galvanized Steel and Stainless Steel
Galvanized Steel Applications:
Construction:Used for steel structures, roofs, walls, door frames, and scaffolding. It balances strength and corrosion resistance, ensuring stability and reducing maintenance costs.
Transportation:Used for car chassis, body frames, highway guardrails, and railway fasteners. It improves the corrosion resistance and extends the service life of parts.
Agriculture:Used for greenhouse frames and agricultural machine parts, suitable for harsh outdoor environments to ensure durability.
Stainless Steel Applications:
Construction & Decoration:Used for building facades, interior decoration, and landscape sculptures. It is beautiful, easy to clean, and adds a modern luxury feel.
Food & Catering:Used for food processing equipment and kitchen utensils. It is non-toxic, corrosion-resistant, and meets hygiene standards.
Medical:Used for medical equipment and hospital facilities. It is resistant to corrosion and compatible with biological tissues, ensuring safety.
Chemical Industry:Used for chemical containers, pipelines, and environmental equipment. It resists chemical corrosion, ensuring stable operations in production and environmental protection.
How Can Manek Help
At Manek, we offer our clients a series of customized services specifically for stainless steel and galvanized steel, including investment casting, sand casting, die casting, CNC machining, sheet metal fabrication as well as various surface treatments.
We also provide a variety of other manufacturing capabilities. You can get quotations for free, such as 3D printing, plastic injection molding and powder coating.
