The four stainless steel sheet finishes you'll run into most are 2B (a smooth, dull grey mill finish), BA (bright annealed, close to a mirror), No. 4 (brushed, with a visible grain), and No. 8 (a polished mirror). 2B is the default and the cheapest; the others cost more because they take extra processing.
The finish you pick changes how the part looks, how easy it is to clean, and even how well it resists corrosion. It also affects fabrication, because a brushed or mirror sheet shows every scratch from handling, bending, and welding. Below we decode the finish names, compare them, and cover what happens to the finish once the sheet becomes a part.
Why stainless finishes have two naming systems
Stainless finishes are labelled under two systems, and suppliers mix them freely. The American system (ASTM A480) uses names like 2B, BA, No. 4, and No. 8. The European standard EN 10088-2 uses codes like 2B, 2R, 2J, and 2P. Some names match and some don't, which is where confusion starts.
The first character in the European code tells you the starting point: 1 means hot rolled (thicker plate), 2 means cold rolled (most sheet). The letter describes what was done after that.
Here's how the common ones line up:
| Common name | EN 10088-2 code | ASTM A480 name | What it looks like |
|---|---|---|---|
| Hot rolled, pickled | 1D | No. 1 | Dull, rough grey; thicker plate |
| Matt mill finish | 2D | 2D | Dull, low-reflective grey |
| Standard mill finish | 2B | 2B | Smooth, slightly reflective grey sheen |
| Bright annealed | 2R | BA | Bright and highly reflective |
| Brushed / dull polished | 2J | No. 4 | Fine directional grain |
| Satin polish | 2K | No. 6 | Smoother, finer directional grain |
| Mirror polished | 2P | No. 8 | Reflects a clear image |
If a drawing just says "stainless, polished", it can mean three different things. Name the finish.
The mill finishes: 2B, 2D, and BA
Mill finishes come off the steel mill's production line rather than out of a polishing shop.
2B is the workhorse. The sheet is cold rolled, heat treated, pickled, then given a light final pass through polished rolls, which leaves a smooth, faintly reflective grey surface. It's flat, consistent, and the base that most brushed and polished finishes start from. For enclosures, brackets, chutes, catering equipment interiors, and anything that will be welded and cleaned, 2B is the sensible choice.
2D skips that final skin pass. It's a little rougher and more matt than 2B and tends to appear on thicker sheet. Fine for industrial work where appearance isn't judged.
BA (bright annealed) is annealed in a protective atmosphere so it comes out bright and reflective. It's often supplied with a plastic film. It looks close to a mirror from a distance, though it isn't as perfect as a polished No. 8. Good for trim and decorative panels where you want shine without the cost of polishing.
Brushed and mirror finishes: No. 4 and No. 8
No. 4 is the brushed finish most people picture when they think of stainless appliances and lift doors. It's made by abrading the sheet in one direction, which leaves a fine grain. It hides fingerprints and small scratches better than bright finishes, which is why it's popular for counters, splashbacks, signage, and shopfitting.
Two things to know about No. 4:
- Grain direction matters. On a drawing, show which way the grain runs relative to the part. Two panels side by side with the grain at 90° to each other look like different materials.
- "No. 4" isn't one exact roughness. It describes the process, not a precise result, so two suppliers' No. 4 can look slightly different. For a run of matching panels, it's worth having them cut from the same batch of sheet.
No. 8 is a mirror polish. It's the most expensive finish, the hardest to keep perfect through fabrication, and it shows everything. Use it where it really earns its place: feature panels, high-end signage, decorative trim.
Does the finish affect corrosion?
Yes, and it's not intuitive. A smoother surface resists corrosion better than a rough one, even on the same grade.
Stainless industry guidance puts the critical roughness at about 0.5 µm Ra for abraded surfaces. Rougher than that, the scratches trap salt and dirt, and the bottom of each groove stays wet longer. That's why a coarse brushed finish on 316 near the sea can tea-stain faster than you'd expect, sometimes worse than a smooth 2B or BA finish on 304.
Practical rules for outdoor and coastal parts:
- Choose a fine brushed finish, or a mill finish like 2B or BA, over a coarse grind.
- Run the grain vertically so water drains along it.
- Expect sheltered surfaces that rain doesn't wash to stain first.
Our posts on the best metal for coastal areas and 304 vs 316 stainless steel cover grade choice for those conditions.
What happens to the finish when the sheet becomes a part
The sheet finish is only the starting point. Fabrication changes it in a few predictable ways:
- Laser-cut edges don't match the face finish. They're usually clean when cut with nitrogen, but they're a different texture.
- Bending can mark the surface where it contacts the tooling, especially on soft or polished finishes. Protective film and clean tooling help.
- Welding leaves heat tint, the straw-to-blue discolouration around the weld. On visible parts it needs to be removed, both for looks and to restore corrosion resistance. Our post on stainless steel weld discolouration explains the options.
- Grinding welds flat on a brushed panel leaves a patch that has to be re-grained to blend in, and it never looks quite as uniform as untouched sheet.
That last point is a design decision. If a brushed or mirror part has visible welds, either accept a blended repair or rethink the joint so the weld sits out of sight.
How to specify the finish on your quote
Be specific. "Stainless" isn't enough, and neither is "brushed". A good finish spec includes:
- Grade and thickness, for example 304, 1.5 mm
- The finish, by name or code: 2B, BA, No. 4 (2J), or No. 8 (2P)
- Which faces matter: one side or both
- Grain direction for brushed sheet, marked on the drawing
- Whether welds must be cleaned, blended, or left as-is
If you need weld cleaning, edge deburring, or other work after fabrication, see our metal finishing service and our overview of types of metal finishing. Then start a metal finishing quote with your drawings, and tell us what the part has to look like when it's done.