If you’re confused between carbon steel and stainless steels, you’re in good company. Even among professionals, it can be difficult to define which is better than which, especially since there are so many types of carbon steel and stainless steel.

In general, high carbon steel is renowned for its hardness and resilience, making it ideal for high-strength applications. You’ll find it in springs, wrenches, cutting tools, and the business end of quality hammers.

On the other hand, stainless steel is known for its corrosion resistance, luster, and strength, making it particularly useful in making medical instruments and cookware. Most stainless steels are also much stronger and tougher than low-carbon steels.

But, when it comes to selecting the right type of steel for your project, you need more information about the properties and unique characteristics of various types of carbon and stainless steel.

This comprehensive guide will explore the key differences between various types of carbon steel and stainless steel to help you make an informed decision based on your specific needs.

What Is Carbon Steel? Definition and Types

Carbon steel is an iron-carbon alloy with a carbon content of 0.15% to 3.4% or more by weight. This type of steel can further be classified into four categories: low, medium, high, and ultra-high carbon steels, depending on the carbon content.

This type of steel is also called plain carbon steel because the main alloying element is carbon with very little manganese, sulfur, silicon, or phosphorus. Thus, it gets most of its properties from the carbon content. The table below summarizes the types of plain carbon steel and their properties.

Type of Steel	Carbon Content	Properties
Low-carbon Steel (Mild Steel)	0.05% to 0.15%	Highly ductile, suitable for stamping machines, auto parts, piping, tubes, and structural materials like angle iron and C-channel.
Medium-carbon Steel	0.1% to 1.29%	Good mix of ductility and strength, used in structures, fabrication of non-pressurized and pressurized tanks, can be heat treated.
High-carbon Steel	0.1% to 3.4%	Very hard, used for cutting materials, seen in kitchen and chef knives and blades in industrial equipment.
Ultra-High Carbon Steel	Up to 4.0%	Extremely hard and brittle, used in high-quality knife sets and tooling for machining softer metals or cutting fine details.

Technically speaking, carbon steel doesn’t exceed 1.5% carbon by weight—anything above that is considered cast iron. Cast iron can have as much as 4% carbon content, the difference being the distribution of carbon within the metal structure.

Lower carbon steels, also known as mild steels, are soft, easy to shape, and easy to machine, which also makes them cheaper. Medium carbon steel gives the best of both sides, being relatively hard, tough, easy to machine, and can be hardened even further by heat treatment and tempering.

In contrast, cast iron’s higher carbon content typically results in the formation of graphite flakes or spheroids throughout the iron matrix. This structural difference gives cast iron its excellent castability and compressive strength but also results in brittleness and less tensile strength compared to carbon steels.

All types of carbon steels can be hardened further by adding other alloying elements such as chromium, molybdenum, and nickel, and this brings us into the territory of stainless steel.

Expert Tip: The structure and properties of carbon steels can be changed through heat treatment, such as quenching, or forming techniques such as cold rolling. Such processes change the distribution of carbon in the iron matrix to make it harder or softer. For example, carbon steels with a martensite structure are incredibly hard and brittle, while

What Is Stainless Steel? Definition and Types

Stainless steel, on the other hand, is an iron alloy that contains a minimum of 10.5% chromium. The addition of chromium gives the steel its unique stainless and corrosion-resistant properties.

Most common types of stainless steel, also called inox, contain other alloying elements that help to improve its properties, such as nickel, molybdenum and manganese. Nickel is one of the most important alloying elements in stainless steel that helps improve its corrosion resistance, weldability, and workability.

Stainless steel’s versatility is evident in its classification into five different groups, each defined by its unique crystalline structure. The table below shows these five types of stainless steel and their properties:

Type of Stainless Steel	Composition	Main Properties and Applications
Austenitic Stainless Steel	18% chromium, 8% nickel	Superior corrosion resistance, excellent formability Used in cutlery, chemical vessels, exhaust systems, and hydraulic components
Ferritic Stainless Steel	12%-30% chromium, under 0.20% carbon	Magnetic, good corrosion resistance, cannot be hardened by heat treatment Used in food handling, ovens, and kitchen sinks
Martensitic Stainless Steel	11.5%-18% chromium, up to 1.2% carbon, includes nickel	High strength, hardness, can be hardened by heat treatment Used in jet engines, gas turbines, valves, and medical instruments
Duplex Stainless Steel	Approx. 22% chromium, 5% nickel, 3% molybdenum	Ultra high strength, improved corrosion resistance, especially against stress corrosion cracking Used in oil, gas, and chemical industries
Precipitation Hardening Stainless Steel	Varies, includes elements like aluminum, copper, niobium	Can be hardened by heat treatment, high tensile strength and corrosion resistance Used in the oil, gas, aerospace, and nuclear power industries

When talking about carbon steel or stainless steel, it helps to mention the American Steel Institute (AISI) numbers for the stainless steel grades you’re referring to. AISI numbers instantly tell us the composition of steel and its expected properties, which helps to differentiate it from the other 100+ grades available.

Comparing the Properties of Carbon Steel and Stainless Steel

The properties of carbon and stainless steels overlap at many points, especially in terms of hardness, toughness, and other physical properties. However, there are some differences that allow us to compare the two types of steel.

The main difference between carbon steel and stainless steel is their chemical composition. Stainless steel is an alloy of iron, chromium, nickel, and some other elements, while carbon steel only has carbon as a major alloying element.

The other main differences are corrosion resistance, strength, and cost.

Corrosion Resistance

Stainless steel is highly resistant to corrosion, primarily due to its chromium content which forms a protective layer on the surface and shields it from corrosion and rust. That’s why stainless steel is ideal for applications such as medical equipment, kitchen utensils, and food processing.

In contrast, carbon steel has relatively low corrosion resistance and is prone to rusting if not adequately protected or treated. Although it can be coated or treated to improve its resistance, carbon steel is better suited for applications where corrosion is less of a concern but strength and durability are prioritized.

Carbon steel is mostly used in the construction industry and the manufacturing of heavy machinery. Thus, the decision between using carbon steel or stainless steel should be guided by the environmental conditions and specific requirements of the application.

Strength and Hardness

When comparing high-carbon steel to stainless steel in terms of mechanical properties, it’s important to consider factors such as strength, hardness, ductility, and weldability. You can learn more about the properties of metals from our Metal University.

High-carbon steel is known for its superior strength and hardness, attributes that are highly sought after for specific applications. However, these advantages come at the expense of reduced ductility and weldability, potentially limiting the range of applications.

On the other hand, stainless steel, while not reaching the same levels of strength and hardness as high-carbon steel, strikes a notable balance among these properties.

Below is a summary comparison of these properties:

• High-carbon steel
  • High strength and hardness
  • Low ductility, meaning it is less able to deform under tensile stress
  • Lower weldability
  • Applications: cutting tools and blades
• Stainless steel (compared to high-carbon steel)
  • Lower strength and hardness compared to high-carbon steel
  • Higher ductility; can deform more easily under tensile stress without breaking
  • Higher weldability makes fabrication and assembly easier
  • Applications: industry, kitchenware, medical instruments, and architecture
• Low-carbon steel (mild steel):
  • Lower strength and hardness than high-carbon steel
  • Higher ductility and malleability; can be easily formed and shaped
  • Very high weldability with minimal pre-weld and post-weld heat treatments
  • Applications: versatile, mostly used in construction, automotive body parts, and household appliances

Remember that while each type of steel—high-carbon, low-carbon, and stainless—has distinct physical properties, they can vary significantly depending on the grade of steel.

Cost

When it comes to cost, carbon steel and stainless steel differ significantly due to their composition and manufacturing processes.

Carbon steel, being simpler in composition and easier to produce, is generally more affordable than stainless steel. The addition of chromium to stainless steel, which imparts its corrosion-resistant properties, also adds to its cost.

However, the durability and longevity of stainless steel can provide long-term cost benefits, making it a valuable investment for certain applications. Below is a comparative overview of the cost aspects of both types of steel.

• Carbon Steel
  • Lower initial cost and cheaper upfront.
  • Easy to manufacture and work
  • Long-term cost: high maintenance costs over time
• Stainless Steel:
• High initial cost due to cost of chromium and nickel
• Complex and costly manufacturing
• Long-term cost: lower overall costs

For applications that demand extreme performance, such as pressure vessels and chemical processing equipment, it’s worth paying extra for the best grades of stainless steel.

Carbon Steel vs Stainless Steel: Applications

Carbon Steel Applications

Carbon steel is widely used in various applications due to its strength and affordability. Low-carbon steel is often used in construction for structural components, pipelines, and even in the automotive industry for body panels.

Medium and high-carbon steel are commonly used in tools, knives, and other applications where wear resistance is key.

Stainless Steel Applications

Stainless steel’s corrosion resistance makes it the material of choice in environments where rust and corrosion are a concern. It is extensively used in kitchen utensils, appliances, medical equipment, and in the chemical and food processing industries.

Additionally, the aesthetic appearance of stainless steel makes it popular for architectural and decorative applications.

Summary: Choosing the Right Type of Steel

Even among the different grades of carbon and stainless steel, selecting the right one for your needs can be difficult. When you add budget constraints and outlier factors such as expansion, magnetism, heat resistance, environmental impact, and regulatory requirements, it becomes even harder to choose.

If corrosion resistance, durability, and strength are the priority, stainless steel is likely your best bet. It offers exceptional durability and resistance to environmental wear and tear, making it ideal for projects that must endure harsh conditions.

Conversely, if your project prioritizes strength and cost-effectiveness, carbon steel may be the more suitable option. It provides substantial strength and cost efficiency but requires protection against galvanic corrosion.

Where to Buy Top-Quality Carbon and Stainless Steels

Both carbon steel and stainless steel are indispensable across various industries, each offering distinct advantages. Understanding the specific properties and benefits of each type can streamline your decision-making process, ensuring you select the ideal material for your needs.

Perhaps a more important consideration is availability and lead time. Sometimes your chosen grade of steel is not immediately available, depending on existing supply chain bottlenecks and other factors.

For these reasons, it’s vital that you work with industry partners who prioritize speed of delivery and customer satisfaction. At Industrial Metal Service (IMS), we are the leading metal suppliers in the Bay Area serving a wide range of industries, from medical to aerospace and semiconductor manufacturing.

As trusted specialists for 30+ years, we have the experience and knowledge to help you find and choose the right type of steel for your projects.

If you buy now, we’ll cut your order and get it out the door in 2–3 days. Talk to Industrial Metal Service specialists today and let us help you get your project going.