Stainless Steel Grades — The Ones Buyers Ask For
The grade number tells you the alloy family — austenitic, ferritic or duplex — and the family, not the exact grade, decides most jobs. This guide covers the grades we quote most often, each with its own page: chemistry limits, mechanicals and the point where it stops being the right choice.
Grades With Their Own Page
A grade page tells you what one grade does — chemistry limits, the PREN number, the forms it comes in, and the point where it stops being the right call. Buyers usually start from the grade, which is why these pages exist.
304 Stainless Steel
304 is the general-purpose austenitic stainless steel — roughly 18% chromium and 8% nickel. It is the default answer for most food, architectural and general corrosion jobs, and it is the wrong answer the moment chlorides or welding enter the picture without the low-carbon L version.
316L Stainless Steel
316L is 304 with molybdenum added (2–3%) for chloride resistance and carbon pulled down to 0.030% for welding. It is the default answer for anything coastal, marine or chlorinated, and the grade to specify whenever a part will be welded in service.
2205 Stainless Steel
2205 is a duplex stainless steel — roughly half austenite and half ferrite — that combines about twice the yield strength of 316L with better chloride and stress-corrosion resistance. It is the answer when 316L is not strong enough or not corrosion-resistant enough, and the cost sits between 316L and super-austenitics.
304L Stainless Steel
304L is 304 with carbon pulled down to 0.030% maximum. The chemistry is otherwise the same, and so is the corrosion behavior — the difference only shows up when the part is welded, because low carbon stops chromium carbide from precipitating at the weld and sensitizing the heat-affected zone.
316 Stainless Steel
316 is the molybdenum-bearing austenitic grade — 304 with 2–3% molybdenum added for chloride and pitting resistance. It is the standard answer for marine, coastal and chemical service that is not welded, and the base from which the low-carbon 316L was developed for welded duty.
201 Stainless Steel
201 is a manganese-substituted austenitic stainless — it replaces part of the nickel in 304 with manganese and nitrogen to hold the austenitic structure. It is not a low-cost replica of 304: it offers useful strength and acceptable corrosion performance indoors, but its lower nickel and chromium reduce pitting resistance and make its ductility and weldability more sensitive to processing.
430 Stainless Steel
430 is a ferritic stainless — chromium-bearing but nickel-free, so it is magnetic and noticeably cheaper than the austenitic 300 series. It resists atmospheric and mild chemical attack well and does not work-harden like 304, which makes it easy to form and draw, at the cost of lower corrosion resistance and no weld ductility.
321 Stainless Steel
321 is 304 stabilized with titanium, which ties up the carbon so it cannot form chromium carbide at the weld or in elevated-temperature service. It is the grade to specify when a welded 304 part will run hot — roughly up to 800 °C in service — where ordinary 304L would lose its corrosion resistance through sensitization.
310S Stainless Steel
310S is a high-alloy austenitic stainless with 24–26% chromium and 19–22% nickel, built for oxidation resistance in continuous high-temperature service up to about 1100 °C. The low-carbon "S" version resists the carbide precipitation that would embrittle the standard 310 in the heat-affected zone.
The three families
What the Grade Number Means
Austenitic — 304, 316L
The 300 series. Non-magnetic in the annealed state, excellent corrosion resistance, the workhorse family. 304 is general purpose; 316 and 316L add molybdenum for chloride resistance. The L means low carbon for welding; 321 adds titanium and 310S adds chromium and nickel for high-temperature service.
Duplex — 2205
Half austenite, half ferrite. Roughly twice the yield strength of 316L with higher PREN, and it resists stress-corrosion cracking that cracks the austenitic grades. The answer for load-bearing chloride service.
Ferritic — 430
The 400 series. Magnetic, no nickel, lower cost. Good for indoor trim and appliance work, poor for welding and chloride service. Usually specified only where cost matters more than corrosion. 201 is the manganese-substituted economy austenitic, often grouped with it for cost-driven indoor work.
Quick selection
Three-Question Shortcut
Does it see chlorides?
No → 304 is usually enough. Coastal or chlorinated → 316L. Seawater or high chloride → 2205 duplex.
Will it be welded?
Yes → specify the L grade (304L, 316L) to avoid sensitization at the weld, whatever the corrosion environment.
Is it load-bearing and hot?
Yes, in chloride service → 2205 duplex resists stress-corrosion cracking that would crack 304 or 316L.