18-8 is one of the oldest names in stainless steel. The numbers refer to the alloy’s two main ingredients: about 18% chromium and about 8% nickel. Chromium gives stainless its corrosion resistance, and nickel gives it a tough, formable structure.
You’ll see 18-8 on older drawings, in catalogs and especially on fasteners and hardware. It’s a convenient label, but it names a family of stainless steels, not one alloy.
Which grades are 18-8?
Several 300 series grades fall within the 18-8 family. Their chromium and nickel ranges all sit close to 18 and 8, but each grade has its own limits, and those small differences change how the material behaves.
| Alloy | UNS | Chromium, % | Nickel, % | What sets it apart |
|---|---|---|---|---|
| 302 | S30200 | 17.00–19.00 | 8.00–10.00 | Higher carbon allowed (.15 max) for strength in cold-rolled tempers |
| 304 | S30400 | 18.00–20.00 | 8.00–10.50 | The most widely used stainless; lower carbon (.08 max) |
| 304L | S30403 | 18.00–20.00 | 8.00–12.00 | Low carbon (.03 max) for better corrosion resistance after welding |
| 305 | S30500 | 17.00–19.00 | 10.50–13.00 | Extra nickel keeps it softer and less magnetic during forming |
Chemistry limits per the AMS and ASTM specifications on our Specification Cross Reference.
What isn’t 18-8
- 301 has less chromium and nickel (16–18% and 6–8%). That lower nickel is what lets it reach higher strength through cold rolling, which makes it a different material from the 18-8 grades.
- 316 / 316L adds 2–3% molybdenum and more nickel for better resistance to chlorides and pitting. It’s a step up in corrosion resistance and is not interchangeable with 18-8.
- 17-7PH® is a precipitation-hardening stainless, not a variation of 18-8, despite the similar-looking name.
Why 18-8 isn’t enough to order
“18-8” tells us the material is in the 302 / 304 family, but not which grade or temper your part needs. A deep-drawn part might call for 305, a welded part for 304L and a spring for Full Hard 302 — all of them “18-8.” Your drawing, purchase order or engineer should specify the alloy and temper, or an AMS specification, which covers both. For example, AMS 5513 is 304 Annealed.
How our material fits
Much of our 18-8 material is certified to more than one grade, which often makes the choice simpler:
- Our 302 / 304 is dual certified to meet both alloys. Why 302 / 304?
- Our annealed 304L is triple certified to 304L, 304 and 302. Why 304L / 304 / 302?
Once you know the alloy and temper, add the thickness, width and quantity, and send it through our Request a Quote form or call (800) 992-5015.
This article is educational information only. Always order to the alloy, temper and specification called for by your drawing or purchase order.