Stainless Steel – What Do All The Numbers Mean?

Whenever we talk about stainless steel, we always use numbers – 304, 163, 18/8 and many more. We also talk about the gauge of the steel, and it can all get very confusing. So, we thought we’d demystify the categorising and classification process by explaining what the different numbers mean.

18/8 and 18/10 are two most common grades of steel, used most often for food preparation and eating utensils. When stainless steel is described this way, it’s to indicate the amount of chromium and nickel the metal contains. For example, 18/8 stainless steel comprises 18% chromium and 8% nickel. Similarly, 18/10 stainless steel is 18% chromium and 10% nickel.

Chromium and nickel are the two most common – and important – alloying elements. Chromium helps bind oxygen to the surface of the steel product to protect against oxidation (rust), especially at higher temperatures. The addition of nickel promotes ductility and toughness, and reduces corrosion in acidic environments. In some grades, nickel also helps to improve weldability.

When it comes to flatware (cutlery) it’s a common misconception that 18/10 is heavier. This isn’t true, and the only real difference is that 18/10 has additional nickel, which makes the cutlery slightly stronger and gives it a better shine.

18/18 and 18/10 are also known as Grade 304 stainless steel, and form part of the 300 series. In addition to chromium and nickel, 304-grade stainless steel is also comprised of up to 0.8% carbon and at least 50% iron.

Stainless steels in the 300 series are classified at austenitic, and can only be hardened by cold working methods. They have good corrosion resistance, are easy to maintain, and keep their strength at high temperatures. Most steel sheet, plate, bar, tube, pipe, and structural products are made from 300 series alloys.

Sometimes you’ll see 18/0 stainless steel, meaning there is 18% chromium but no nickel. This metal falls into the 400 series, and is commonly called 430 stainless steel. 400 series alloys lack the corrosion resistance of those in the 300 series, and they are magnetic, unlike 300 series alloys.

Stainless steel food containers are often made from 200 series steel. This is usually a less expensive option than the 304 grade, as the nickel is replaced with manganese. 200 grade stainless is still food safe, but is not as high quality, nor as corrosion resistant, as 304.

When we talk about the “gauge” of stainless steel, we’re referring to the thickness of the sheet metal used to make it. The higher the gauge, the thinner the metal – so 14 gauge is thicker than 16 gauge.

Steelmor is leading stockist and manufacturer of 300 and 400-grade stainless steel products in South Africa. Visit our Products page to view our whole range.