Galvanized Steel vs Stainless Steel: Differences and Which is Better

When we think of rust-resistant steel, stainless steel often comes to mind, as does galvanized steel, which undergoes a galvanization process to enhance its corrosion resistance. However, what specifically sets these two kinds of steel apart when it comes to resisting corrosion? So, which option is more suitable for your project?

In this guide, we will explore the differences between stainless steel and galvanized steel in terms of their properties, applications, and their respective pros and cons, helping you make the best decision for your needs.

What Exactly is Galvanized Steel?

Galvanized steel, or zinc-coated steel, is made from carbon and structural steel. It uses hot-dip galvanizing and electroplating methods to form a protective zinc coating that adheres to the steel surface. Typically in flat sheets or hollow shapes, it meets ASTM A123 standards. In contrast to stainless steel, which depends on chromium, galvanized steel depends on zinc for rust prevention. It is widely used in construction, automotive, and appliances for its durability and affordability.

Galvanization Process of Galvanized Steel

1. Cleaning:
   The steel is cleaned to remove dirt, grease, and rust using chemical baths or sandblasting.
2. Dipping in Molten Zinc:
   After cleaning, the steel is dipped into molten zinc at approximately 450°C (842°F). The zinc attaches to the steel, forming a shielding layer.
3. Cooling and Inspection:
   The steel is cooled and inspected to ensure an even zinc coating.
4. Electro-Galvanizing (for smaller parts):
   For smaller parts, zinc is applied using an electric current in a process called electro-galvanizing.

The zinc layer protects the steel by preventing air and moisture from reaching it, ensuring corrosion resistance.

What is Stainless Steel?

Stainless steel (also called inox) is made of iron, chromium (at least 10.5%), nickel, and carbon. It meets ASTM A240 standards and resists corrosion due to a chromium oxide layer. The main types are austenitic, ferritic, martensitic, duplex, and precipitation hardening. It comes in sheets, bars, and tubes. Stainless steel is strong, durable, and heat-resistant, used in construction, food processing, and medical equipment. Common processing methods include welding, machining, and forming.

Click here for a comprehensive guide on stainless steel!

Chemical Properties of Galvanized Steel vs Stainless Steel

Galvanized steel and stainless steel vary in chemical makeup and functionality. Below is a brief comparison of their key properties, including composition, corrosion resistance, chemical reactivity, and durability.

1. Composition

• Galvanized Steel:
  Galvanized steel is composed of approximately 99% carbon steel and 1% zinc. The zinc layer offers protection but does not change the steel’s chemical structure.
• Stainless Steel:
  Stainless steel is a mixture mainly consisting of 70% iron and at least 10.5% chromium, with additional elements such as nickel or molybdenum. The chromium creates an inactive layer of chromium oxide on the surface, providing rust resistance.

2. Corrosion Resistance

• Galvanized Steel:
  The zinc coating on galvanized steel provides sacrificial protection, meaning the zinc corrodes first, protecting the underlying steel. However, once the zinc layer is worn away, the steel becomes vulnerable to corrosion.
• Stainless Steel:
  Stainless steel offers better resistance even after surface damage, thanks to its self-repairing passive oxide layer. This layer regenerates, providing long-term protection. Both galvanized and stainless steel resist corrosion better than regular carbon steel, but stainless steel has the advantage of lasting protection.

3. Reactivity to Chemicals

• Galvanized Steel:
  Galvanized steel is susceptible to acids and alkalis, which can break down the zinc coating. Exposure to saltwater or acidic environments will significantly reduce its lifespan.
• Stainless Steel:
  Stainless steel resists most acids, bases, and chemicals, making it highly suitable for environments with harsh chemicals or saltwater exposure.

Physical Properties of Galvanized Steel vs Stainless Steel

Galvanized steel and stainless steel differ not only in their chemical makeup but also in their physical properties. Key factors such as durability, thermal conductivity, weldability, and magnetism are important when choosing the right material for a project. Below is a brief overview of how these characteristics compare.

1. Durability

• Galvanized Steel:
  It offers decent durability but depends on the thickness of the zinc coating. Over time, the coating wears off, reducing its lifespan.
• Stainless Steel:
  Stainless steel is highly durable, resisting corrosion and wear over a longer period, making it ideal for harsh conditions.

2. Thermal Conductivity

• Galvanized Steel (85-90 W/m·K):
  Galvanized steel has moderate thermal conductivity, suitable for general use but not high temperatures. Heating it above zinc’s melting point can cause the zinc to liquefy and separate from the steel, posing burn or fire risks.
• Stainless Steel (16-17 W/m·K):
  Stainless steel has lower thermal conductivity, meaning it doesn’t transfer heat as efficiently, which can be useful in high-temperature applications.

3. Melting Point

• Galvanized Steel (Base Steel ~1425-1540°C, Zinc Coating ~419°C): The base steel in galvanized steel has a high melting point, similar to other steels. However, the zinc coating melts at a much lower temperature (~419°C). When exposed to high heat, the zinc can melt and separate, limiting its use in high-temperature environments.

• Stainless Steel (1400-1450°C): Stainless steel has a consistently high melting point, making it suitable for high-temperature applications. Unlike galvanized steel, it does not have a low-melting-point coating, which allows it to maintain its integrity under heat.

4. Weldability

• Galvanized Steel:
  Welding galvanized steel is difficult because of the zinc layer, which can emit dangerous fumes and reduce the strength of the weld.
• Stainless Steel:
  Stainless steel is easier to weld and does not release toxic fumes, making it preferable for welded structures.

5. Magnetism

• Galvanized Steel:
  The magnetism of galvanized steel depends on the base steel used. If the base steel is magnetic, the zinc layer will not disrupt its magnetic characteristics. Thus, galvanized steel retains the magnetic response of the original material.
• Stainless Steel:
  Stainless steel’s magnetism varies by alloy. Austenitic stainless steel is the least magnetic, while other alloys, depending on their iron content, can exhibit varying levels of magnetism.

Mechanical Properties Comparison of Galvanized Steel vs Stainless Steel

When comparing the mechanical properties of galvanized steel and stainless steel, characteristics such as tensile strength, yield strength, ductility, strength, and toughness determine how each material will perform under stress and in harsh environments. 

1. Tensile Strength

• Galvanized Steel:
  Galvanized steel’s tensile strength depends on the base steel, usually structural or carbon steel. Since the zinc coating does not affect the strength, its tensile strength typically ranges from 370 to 550 MPa (54,000 to 80,000 psi), similar to the base material.
• Stainless Steel:
  Stainless steel is stronger than galvanized steel in terms of tensile strength, ranging from about 515 MPa to as high as 1300 MPa (75,000 to 188,500 psi), depending on the alloy. This makes stainless steel the better choice for high-load applications.

2. Yield Strength

• Galvanized Steel:
  Yield strength for galvanized steel is based on the underlying steel and typically falls between 230 and 350 MPa (33,000 to 50,000 psi). The zinc layer does not change the steel’s yield strength.
• Stainless Steel:
  Stainless steel has a higher yield strength than galvanized steel, with values between 275 and 620 MPa (40,000 to 90,000 psi), making it more resistant to deformation under stress.

3. Ductility

• Galvanized Steel:
  Galvanized steel retains the same ductility as the base steel used, which often surpasses that of stainless steel. Ductility is generally around 15% to 30% elongation at break, allowing it to stretch without breaking.
• Stainless Steel:
  Stainless steels are more ductile, especially the austenitic types, with elongation at break typically ranging from 40% to 60%, making them easier to mold without cracking.

4. Toughness

• Galvanized Steel:
  Galvanized steel has moderate toughness, but the zinc coating can become compromised, especially in cold environments, which weakens its performance. Its impact strength is generally lower than that of stainless steel.
• Stainless Steel:
  Stainless steel exhibits excellent toughness, particularly in low temperatures. It resists cracking or breaking under stress better than galvanized steel, making it ideal for impact-resistant applications.

5. Strength

• Galvanized Steel:
  Galvanized steel has good strength due to its carbon steel base, but the zinc coating does not enhance structural strength.
• Stainless Steel:
  Stainless steel is stronger than galvanized steel, especially in high-stress or extreme environments, thanks to its alloy composition.

Other Comparison of Galvanized Steel vs Stainless Steel

In addition to mechanical and chemical characteristics, there are several other factors to consider when comparing galvanized steel and stainless steel. These include cost, appearance, maintenance, and environmental impact.

1. Cost

• Galvanized Steel:
  Galvanized steel is generally more affordable due to the lower cost of carbon steel and the relatively simple zinc-coating process. It’s an affordable choice for tasks that don’t demand high durability.
• Stainless Steel:
  Stainless steel costs more because of alloy components like chromium and nickel. Its increased cost is explained by excellent rust resistance and durability, particularly in tough conditions.

2. Appearance

• Galvanized Steel:
  Galvanized steel has a dull, matte finish look that can vary depending on the galvanization process. It is not typically chosen for projects where aesthetics are a key concern.
• Stainless Steel:
  Stainless steel has a shiny, polished finish that is often more aesthetically appealing. It is commonly utilized in situations where aesthetics are important, such as in building designs and premium appliances.

3. Maintenance

• Galvanized Steel:
  Galvanized steel requires periodic inspection, especially in harsh environments where the zinc layer may corrode over time. If the zinc coating wears off, it will need recoating to prevent rusting.
• Stainless Steel:
  Stainless steel requires little upkeep, as its self-healing oxide layer shields it from rust. It requires minimal upkeep and does not need protective coatings or treatments.

4. Environmental Impact

• Galvanized Steel:
  Galvanized steel can impact the environment due to zinc runoff during production and disposal. Recycling is also more complex because once the zinc layer wears off, it becomes standard steel and needs to be galvanized again.
• Stainless Steel:
  Stainless steel is easier to recycle. It can be melted down, with impurities removed or adjusted, and reused without extra processing. Its long life and minimal maintenance make it more eco-friendly over time.

5. Weight

• Galvanized Steel:
  Galvanized steel has a similar weight to regular carbon steel, with the zinc coating adding only a slight increase in overall weight. It is generally heavier than stainless steel when comparing similar thicknesses.
• Stainless Steel:
  Stainless steel is lighter than galvanized steel due to its alloy composition, despite its superior strength. This makes it a desirable option when weight is a key consideration, particularly in building and transport projects.

In summary, stainless steel offers better corrosion resistance and strength than galvanized steel in extreme environments. However, galvanized steel is easier to process and weld, costs less, and resists corrosion better than other carbon steel.

Applications of Galvanized vs Stainless

Due to their distinct characteristics, galvanized steel and stainless steel are extensively utilized in various industries. Galvanized steel is often chosen for cost-effective corrosion resistance in moderate environments, while stainless steel is preferred for applications requiring high durability and resistance to extreme conditions.

Galvanized Steel Applications:

• Construction (roofs, structural beams, and fencing)
• Automotive parts (frames, body panels)
• Agriculture (storage silos, irrigation systems)
• Outdoor structures (gates, guardrails)
• Electrical poles and transmission towers
• HVAC systems (ductwork and piping)
• Appliances (washing machine drums, air conditioners)

Stainless Steel Applications:

• Food and beverage processing equipment
• Medical instruments and surgical tools
• Chemical and pharmaceutical industries (tanks, reactors)
• Marine environments (boats, docks, and hardware)
• Architecture (handrails, facades, and decorative elements)
• Automotive and aerospace parts (exhaust systems, fasteners)
• Kitchenware and household appliances (sinks, cutlery, countertops)

Common Applications of Galvanized Steel and Stainless Steel

Galvanized steel and stainless steel are used together in many industries for their durability and corrosion resistance. Here are some shared applications:

• Construction: Used in building frames, supports, and roofing. Galvanized steel is more cost-effective, while stainless steel offers better corrosion resistance.
• Automotive: Both are used in car bodies, chassis, and components to resist corrosion and increase lifespan.
• Home Appliances: These are found in the outer shells of refrigerators, washing machines, and other appliances due to their durability and appearance.
• Transportation: Applied in traffic signs, guardrails, and bridges. Favored for its ability to withstand rust, simple maintenance, and non-interaction with food substances. It is commonly applied in machinery, containers, and the preparation of food products.
• Agriculture: Used in greenhouse frames, water tanks, and fencing, providing corrosion protection and durability.

Galvanized Steel and Stainless Steel Compare in the Food Industry

Stainless Steel: Stainless steel is preferred for its ability to resist corrosion, low maintenance requirements, and safe interaction with food. It is commonly applied in machinery, storage, and food processing industries.

Galvanized Steel: Not suitable for direct food contact due to possible corrosion of the zinc coating in acidic environments. Mostly used for non-contact structures like shelving and racks.

Galvanized Steel and Stainless Steel Comparison in the Medical Industry

Stainless Steel: Essential for medical tools, implants, and devices because it is easy to sterilize, durable, and highly resistant to corrosion.

Galvanized Steel: Unsuitable for direct medical use due to the risk of the zinc coating chipping and its rough surface, making it hard to clean. It is mainly used in non-sterile infrastructures.

Related Reading
Medical Grade Stainless Steel.

Which is better, galvanized or stainless steel?

So, which one is better, galvanized steel or stainless steel? The best choice depends on your particular requirements. Below is a comparison based on key factors like cost, maintenance, durability, safety, and common usage scenarios.

1. Based on Characteristics

• Cost:
  Galvanized steel is the better option when cost is a primary concern. Its lower production cost and affordability make it ideal for projects with budget constraints, especially where extreme durability is not essential.
• Maintenance:
  Stainless steel is the preferred choice for long-term, low-maintenance use. Its self-healing oxide layer ensures that it requires little upkeep, unlike galvanized steel, which may need recoating over time.
• Durability:
  Stainless steel is the better option for environments where durability is critical, such as harsh weather or corrosive conditions. Its superior corrosion resistance ensures it lasts longer without degradation, whereas galvanized steel may wear down in tough conditions.
• Safety:
  For food and medical applications, stainless steel is the clear winner due to its non-toxic, non-reactive properties. It is safer for direct contact with food or medical devices, while galvanized steel’s zinc coating can deteriorate, posing contamination risks.

2. Based on Usage Scenarios

• Marine Environments:
  In marine environments or humid conditions, stainless steel is the superior option because of its outstanding corrosion resistance. Galvanized steel can rust as the zinc coating wears off, making it less reliable in such environments.
• Outdoor Structures:
  Galvanized steel is the better option for general outdoor use in low-corrosion environments due to its cost-effectiveness. However, for structures exposed to harsh weather or corrosive conditions, stainless steel is the better choice because of its superior long-term durability.
• Food Industry:
  Stainless steel is the optimal choice for any use that involves direct food contact. Its non-reactive, easy-to-clean surface ensures food safety. Galvanized steel is only suitable for non-contact uses, like shelving or structural supports.
• Medical Field:
  Stainless steel is the preferred option in medical applications because of its sterility, corrosion resistance, and durability. Galvanized steel is unsuitable for direct contact in sterile environments but may be used in non-sterile areas like support structures.

The decision between galvanized steel and stainless steel hinges on your particular requirements: galvanized steel is an economical option for environments with minimal corrosion, whereas stainless steel provides greater durability, safety, and corrosion resistance in more demanding conditions and specialized fields.

How long will galvanized steel last before it rusts?

Depending on environmental conditions, galvanized steel can last 20 to 50 years before rusting. In more corrosive environments, its lifespan may be shorter.

Is Galvanized Steel Suitable for Outdoor Use?

Yes, galvanized steel is suitable for outdoor use, particularly in low-corrosion environments. The zinc coating shields the steel from rust and increases its longevity. However, in highly corrosive environments, such as coastal areas, the coating may degrade faster, making stainless steel a better option for long-term outdoor durability.

What is the Highest Grade of Stainless Steel?

The most commonly used high-grade stainless steel is Grade 316. It includes extra molybdenum, which improves its corrosion resistance, especially against chlorides and aggressive chemicals. This makes it ideal for marine environments and industrial applications requiring maximum corrosion protection.

Is Zinc Waterproof？

No, zinc is not waterproof. While it provides a protective barrier against moisture, prolonged exposure to water can still lead to corrosion, especially in harsh environments.

Will Galvanized Steel Rust?

While the galvanized coating provides some protection, damage from welding or impacts exposes the steel to air and water, increasing rust risk. Environmental factors like humidity, salt spray, and pollutants can further accelerate corrosion, leading to eventual rusting of galvanized steel.

Find the Steel for Your Project

At SteelPRO Group, we have the expertise and inventory to meet all your steel needs, whether you’re looking for galvanized steel, stainless steel, semi-finished products, or fully finished components. With a large stock and a commitment to timely delivery, we ensure that your project stays on track. If you’d like to read more articles on galvanized or stainless steel, please visit our blog page.

Let us help you find the perfect steel solution—contact SteelPRO Group today and get started!