316 Stainless Steel?

Why should 316 grade stainless steel be used for labels and nameplates?

The simple answer is that there is no reason not to. In any outdoor environment in the UK, and particularly near the sea, 304 grade will stain and rust, 316 grade will not. Even in some indoor environments, 304 stainless steel can discolour. 304 grade stainless steel should never be used for outdoor signage anywhere in the UK.

316 grade has been designed to resist corrosion. It has a higher nickel content and contains molybdenum, and this gives it higher corrosion resistance, especially at higher temperatures. For engineering purposes, this means structures made from 304 grade will fail in certain environments, but 316 will not.

For the purpose of nameplates, labels, and signs, what matters is not the corrosion itself, it is the discolouration it causes. This can be merely aesthetic, a stainless steel sign covered in rusty stains looks horrible, or it could be important to make sure the information on a nameplate remains readable.

Corrosion of the surface of stainless steel is localised on a microscopic scale, causing pitting, and a discolouration called tea staining. This produces dark dots and rusty streaks on the surface, which could make it difficult to tell a 3 from an 8 on a label, or a D from a B. This is the reason why offshore labels are always specified as 316 grade stainless steel.

Most manufacturers will try to sell you 304 grade, not because there is a big difference in material cost (typically less than 1p per label) but because they are not very good at etching 316 grade. Etching is controlled corrosion, and 316 grade is designed to resist corrosion, so it is more difficult to etch if you do not have the necessary equipment and expertise. They therefore use 304 grade for everything, no matter where it is going, and charge a large premium for 316 grade.

We use 316 grade for everything, because we cannot know where every sign and label will be used. It therefore makes sense to make everything suitable for either indoor or outdoor use.

For some environments, the choice is not as simple as using 304 or 316 grade stainless steel. See our guide to marine signage & nameplates.