Home » What Are the Five Types of Stainless Steel? Material Guide What Are the Five Types of Stainless Steel? Stainless steel isn’t a single material. It’s a group of iron-based alloys that all contain at least 10.5 percent chromium, and the way that chromium is balanced with nickel, molybdenum, carbon, and other elements produces very different results. 5 min read • October 2026 • Ryan Conte Understanding the types of stainless steel is the first step toward choosing a grade that meets your project’s strength, corrosion resistance, and budget requirements. The industry sorts stainless steel into five families based on microstructure: austenitic, ferritic, martensitic, duplex, and precipitation-hardening. This guide breaks down the five types of stainless steel, the grades within each family, and where each is typically used. Knowing how the families differ helps you avoid paying for performance you don’t need, or specifying a material that fails in service. Austenitic Stainless Steel: The Most Common of the Five Types Austenitic stainless steel is the largest of the stainless steel families and accounts for the majority of stainless steel produced worldwide. It combines chromium with significant nickel, which gives it excellent corrosion resistance, formability, and weldability. Austenitic grades are non-magnetic when annealed, and they can’t be hardened by heat treatment, although cold working increases their strength. 304. The general-purpose workhorse, with roughly 18 percent chromium and 8 percent nickel. Stainless Shapes stocks 304 stainless steel in bar, plate, channel, beam, and tube for food equipment, architectural work, and general fabrication. 316. Adds 2-3% molybdenum for improved resistance to chlorides, making it the standard choice for marine and chemical environments. L grades and specialty variants. 304L and 316L carry lower carbon for welding, while grades like 303, 321, and 310 are chosen for machinability, stabilization, and high temperature service. Austenitic stainless does have limits. Standard grades can pit in high chloride environments, and both 304 and 316 can be prone to stress corrosion cracking when exposed to chlorides at elevated temperatures. For most general applications, though, austenitic grades offer the best all-around balance, which is why they’re the default starting point for many projects. Need Help Choosing the Right Grade? Tell us about your project and our team will help. Δ Ferritic Stainless Steel: Magnetic and Cost-Effective Ferritic stainless steels are 400-series alloys with 10.5 to 30 percent chromium and little or no nickel, which keeps them less expensive than austenitic grades. They’re magnetic, offer moderate corrosion resistance, and resist stress corrosion cracking well. They can’t be hardened by heat treatment, and they’re harder to form and weld than austenitic grades, especially in thick sections. 409. A low-cost grade used in automotive exhaust systems and agricultural equipment. 430. The most common ferritic grade, found in appliance panels, kitchen equipment, and interior trim. Best fit. Indoor or mildly corrosive environments where cost matters more than maximum corrosion resistance. Because ferritic grades contain little nickel, their prices are less affected by swings in the nickel market. The trade-off is lower toughness, particularly in thick welded sections and at low temperatures, so they’re rarely the right pick for heavy structural work. Martensitic Stainless Steel: Hardenable Grades for Strength and Wear Martensitic stainless steels are also 400-series alloys, but with higher carbon content that allows them to be hardened by heat treatment. They’re magnetic and offer high strength and wear resistance, though their corrosion resistance is lower than austenitic grades. That makes them a good fit when hardness matters more than performance in harsh environments. 410. The general-purpose martensitic grade, used for valves, pump shafts, and fasteners. 416. A free-machining version of 410, common in shafts, fasteners, and precision-machined parts. Stainless Shapes supplies 416, including heat-treated Condition T. 420 and 440C. Higher carbon grades for cutlery, surgical tools, bearings, and blades. 440C is among the hardest stainless grades available. The hardening process is similar to what’s used on carbon and tool steels: the material is heated, quenched, and then tempered. Tempering temperature controls the balance between hardness and toughness, so martensitic grades are usually supplied in a specific heat-treated condition that should be confirmed before ordering. Furthermore, for a prompt and accurate quote, call us today. CALL - 866-788-1385 Duplex Stainless Steel: Strength and Chloride Resistance Combined Duplex stainless steel has a mixed microstructure of roughly equal parts austenite and ferrite. The result is about twice the yield strength of standard 304 and 316, along with strong resistance to chloride pitting and stress corrosion cracking. Duplex is magnetic and is generally limited to service temperatures below about 600°F. 2205. The standard duplex grade, used in offshore, chemical processing, and desalination equipment. 2507 super duplex. Higher chromium, molybdenum, and nitrogen for the most demanding chloride environments. Why choose it. Higher strength allows for thinner sections, which can offset higher material costs on larger projects. Fabrication requires more care than with austenitic grades, since welding procedures need to preserve the balance between the two phases, and prolonged exposure to high temperatures can make duplex brittle. Lower nickel content also makes pricing more stable than that of high-nickel austenitic grades. Duplex grades are specialty materials, and Stainless Shapes can source them through our custom metal sourcing service. Not Sure If You Need the Standard or "L" Grade?Our team can review your welding specs and environment to recommend the right alloy — no obligation. Talk to a Specialist Precipitation-Hardening Stainless Steel: Maximum Strength Through Aging Precipitation-hardening (PH) stainless steels get their strength from a two-step heat treatment: solution treatment followed by aging at a relatively low temperature. The result is tensile strength approaching or exceeding 200 ksi in some conditions, with corrosion resistance comparable to 304 and minimal distortion during aging. 17-4 PH. The most widely used PH grade, available in H conditions such as H900, H1025, and H1150, each with a different balance of hardness and toughness. Our 17-4 PH H condition page breaks down the hardness values for each treatment. 15-5 PH. Similar to 17-4 PH, with improved transverse toughness and ductility. 13-8 PH. One of the highest strength PH grades, commonly used in aerospace structural parts. The aging step is what makes PH grades so versatile. The material is typically supplied in the solution-annealed condition, which is easier to machine, then aged after machining to reach final strength. Different aging temperatures produce different H conditions, so engineers can dial in the mix of strength and toughness a part requires. Stainless Shapes supplies all three grades, heat-treated by a NADCAP-accredited partner. Grade 304 — Food & Beverage: Ideal for kitchen fixtures, tanks, and processing equipment in controlled environments with minimal salt or chemical exposure. Grade 316 — Marine & Coastal: Required for docks, railings, and hardware exposed to saltwater. Molybdenum content protects against chloride-induced pitting. Grade 316 — Chemical Processing: Resists acid, chloride, and chemical washdowns that would pit standard 304. Grade 304 — General Fabrication: Cost-effective for structural frames, enclosures, and indoor components where corrosive conditions are absent. ✓ Choose 304 When: Controlled or indoor environments Support frames, enclosures, and fasteners Minimal chloride exposure Cost-conscious general fabrication Architectural and decorative applications ✓ Choose 316 When: Saltwater and coastal environments Chemical washdowns and acid exposure Oil & gas or wastewater treatment Marine infrastructure Pharmaceutical or medical-grade equipment Key Takeaways On the Types of Stainless Steel 1 There are five types of stainless steel: austenitic, ferritic, martensitic, duplex, and precipitation-hardening, grouped by microstructure. 2 Austenitic grades like 304 and 316 are the most common, offering excellent corrosion resistance and formability, and they’re non-magnetic and not hardenable by heat treatment. 3 Ferritic and martensitic grades are magnetic 400-series steels, with ferritic grades like 430 offering low cost and martensitic grades like 410, 416, and 440C hardening through heat treatment. 4 Duplex stainless steel combines austenite and ferrite, yielding roughly twice the yield strength of 304 and 316 stainless steel, with strong chloride resistance. 5 Precipitation-hardening grades like 17-4 PH, 15-5 PH, and 13-8 PH achieve their highest strength through aging, with corrosion resistance comparable to that of 304. Choosing among the different types of stainless steel comes down to balancing corrosion resistance, strength, formability, and cost. Stainless Shapes supplies austenitic, martensitic, and precipitation-hardening grades including 304, 316, 416, 17-4 PH, 15-5 PH, and 13-8 PH, and can source duplex and other specialty grades on request. If you’re not sure which family fits, start with the environment the material will face, then work through strength, fabrication, and budget requirements. Call 800-748-9811 or request a quote online, and our team will help you identify the right type and grade for your project. The Cost of Choosing Wrong Using 304 in high-chloride environments can cause pitting within months, leading to replacement costs that far exceed the price difference between grades. Our experts can help you select the right grade the first time. Still Not Sure Which Grade You Need? At Stainless Shapes, we work with engineers, fabricators, and procurement teams to identify the right material for the job. We stock a broad range of grades and forms — beams, channels, angles, flats, rounds, and more. Get Expert Help Choosing Call 866-788-1385 Quick Contact We’ll get back to you within one business day Δ
