18-8 Stainless Steel vs 304 Stainless Steel: Which Is Best for Your Fastening Needs?
With so many different grades of stainless steel available, it’s easy to feel overwhelmed when selecting the right fastener for your project. This confusion can be compounded when you realize that two of the most common materials you’ll encounter often appear interchangeable. In fact, 18-8 stainless steel and 304 stainless steel are often so similar in performance that they can seem interchangeable.
However, subtle distinctions in chemical makeup and specification standards can impact long-term performance, cost, and corrosion resistance. This guide breaks down what sets these two stainless options apart, how they perform in real-world environments, and how to choose the best fastener for your job. At Fasteners Etc., Inc., we help customers cut through the confusion with clear guidance and high-quality stainless fastening and anchoring solutions.
What Is 18-8 Stainless Steel?
18-8 stainless steel is a broad term for austenitic stainless-steel alloys with an 18% chromium and 8% nickel content. This formulation is the foundation of many common stainless steel fastener materials and is used in everything from kitchen equipment to automotive hardware.
Key properties of 18-8 stainless steel include:
- Excellent corrosion resistance: Chromium promotes rust resistance by forming a passive oxide layer on the surface.
- Durability: This hard material resists deformation, cracking, and general wear.
- Non-magnetic behavior: Most 18-8 nuts or bolts don’t have magnetic properties in their annealed state, making them safe to use around sensitive equipment.
- Versatility: This material performs well in industrial, household, and food-grade environments.
18-8 is considered the family group that encompasses multiple alloys, including 304, 302, 305, 316, and others. This means when a fastener is labeled 18-8, its exact composition can vary slightly from one batch to another. However, despite this variability, it’s consistent and performs well in general applications. Additionally, its affordability and versatility make it one of the most widely used stainless materials in modern fasteners.
What Is 304 Stainless Steel?
304-grade stainless steel is a specific, highly standardized grade within the 18-8 family. It follows strict composition rules defined by the American Iron and Steel Institute (AISI) and the American Society of Testing and Materials (ASTM).
To be classified as 304 stainless steel, the material must be 18% chromium and 8-10% nickel. It needs to have a low carbon content, no higher than 0.08%. These tighter controls provide consistent performance, which is especially important in industrial and food-grade applications.
Other advantages of 304 stainless steel include:
- Strong corrosion and oxidation resistance: It performs well in environments with regular moisture exposure and in mildly corrosive environments.
- High ductility and formability: 304 stainless steel can be easily shaped without cracking, making it ideal for forming complex fastener heads or other shapes.
- Excellent weldability: This material is common in environments where stainless structures or equipment must be welded without degrading the material.
Because 304 is so reliable and consistent, it remains the world’s most used grade of stainless steel. It is especially common in hardware, such as fasteners and washers, for food processing and medical equipment.
Key Differences Between 18-8 and 304 Stainless Steel
Although 18-8 and 304 are similar, there are meaningful differences between these two types of stainless steel. These distinctions are worth understanding when choosing a fastener.
Chemical Composition
Both contain approximately 18% chromium and 8% nickel. However, 18-8 is a general category with a small range of acceptable compositions, while 304 follows precise AISI and ASTM standards.
Additionally, some 304 alloys may contain small amounts of trace elements such as manganese, silicon, molybdenum, or iron. These slight variations can affect performance but are often negligible for routine use.
Corrosion Resistance
Both 18-8 and 304 stainless steel resist rust well, which makes them ideal for indoor and outdoor applications. However, 304 stainless performs better in high-moisture or mildly corrosive environments. It provides slightly greater resistance to pitting and crevice corrosion, especially in areas where chlorides, including saltwater, are present.
Despite its strengths, even 304 has limitations if it’s frequently exposed to harsh chemicals or marine environments. In those cases, 316 stainless steel outperforms both 18-8 and 304 stainless steels because it contains extra molybdenum. This extra strength resists pitting and rusting.
Mechanical Properties
In annealed form, 18-8 and 304 stainless steels share almost identical mechanical characteristics, including:
- High tensile strength: 18-8 stainless steel has a tensile strength of 500-750 megapascals (MPa), while 304 stainless steel has a tensile strength of 540-750 MPa.
- Strong yield strength: Both have a yield strength of approximately 215 MPa.
- Excellent ductility: 18-8 may have a higher hardness and resistance to deformation, but 304 is more flexible and easier to work with. However, they can both be easily bent and shaped at room temperature.
- Great cold working performance: When cold worked, the hardness of both increases significantly, which means they are less likely to deform further.
Cost and Availability
18-8 stainless steel tends to be more cost-effective and affordable because it encompasses a wider range of alloys. Conversely, 304 may cost slightly more due to its tighter specifications and guaranteed quality.
For bulk purchasing or general-purpose fasteners, many buyers choose 18-8 for its value. If applications require precise material certification, 304 is usually preferred by buyers and engineers.
Applications of 18-8 and 304 Stainless Steel Fasteners
Both stainless grades are used across industries due to their reliability, mechanical strength, and corrosion resistance. Typical applications include:
- Automotive assemblies and components
- Food processing equipment in commercial kitchens and household cookware
- Medical systems and lap equipment
- Architectural and construction hardware
- Heating, ventilation, and air conditioning (HVAC) systems and mechanical assemblies
- DIY projects, manufacturing, and light industrial work
Their versatility is one of the reasons stainless fasteners remain popular in modern engineering and fabrication.
When to Use Each Stainless-Steel Grade
Because 18-8 and 304 stainless steel are extremely similar, understanding when to select one over the other helps maximize performance and cost efficiency.
Use 18-8 Stainless Steel When:
- You need general-purpose fasteners for indoor or lightly exposed environments.
- You need to save on cost without sacrificing reliability.
- The application includes high-strength automotive, general manufacturing, cabinetry, machinery, or indoor fixtures.
- You don’t require strict AISI or ASTM certification.
Use 304 Stainless Steel When:
- You’re using the fastener in harsh environments with consistent moisture, mild chemicals, or temperature fluctuations.
- You need superior corrosion resistance compared to general 18-8 alloys.
- The project requires precise, certified material specifications, such as in food processing, medical devices, architectural builds, and industrial machinery.
- You want material consistency and guaranteed quality from batch to batch.
Choosing the Right Fastener for Your Project
When you’re deciding on the proper stainless-steel grade for your project, you need to consider more than just corrosion resistance. You also need to keep in mind the environment and any performance requirements, including:
- Exposure levels to humidity, chemicals, salt, and cleaning agents
- Strength needs, such as load-bearing requirements and vibration resistance.
- Cost and whether you’re purchasing a high volume of fasteners or are undertaking a specification-driven project
- Certifications, industry standards, or safety requirements
When in doubt, consulting a fastener specialist is the most reliable way to ensure your hardware works long-term. Matching the right fastener to the application prevents failures, extends your equipment's lifespan, and keeps projects on schedule.
Fasteners Etc., Inc. Is Your Trusted Source for Stainless Fasteners
Both 18-8 and 304 stainless steel offer excellent performance, but the best choice depends on your environment, budget, and specification requirements. Fasteners Etc., Inc. provides a wide selection of high-quality stainless-steel fasteners backed by expertise you can trust.
Whether you’re sourcing fasteners for manufacturing, construction, automotive work, or precision machining applications, our team can help you find the right material for long-lasting, corrosion-resistant performance. Need help selecting the right stainless-steel fasteners? Contact us today or request a quote.