The difference between 18/8 and 18/10 stainless steel is in name only, as the two steel alloys are actually completely identical. The numbers in 18/8 steel specify the amount of chromium and nickel used in making the steel. 18/8 steel contains 18 percent chromium and 8 percent nickel. 18/10 stainless steel is a marketing gimmick that suggests a more rust-resistant steel, while in reality 18/10 stainless steel contains the same amounts of chromium and nickel as 18/8 steel.
Steel producers add chromium and nickel to steel because these two metals prevent rust. Therefore, the higher the amount of nickel and chromium a grade of stainless steel contains, the more resistant it is to rust. However, using too much chromium and nickel in the steel production process results in a finished product that is highly resistant to rust, but softer and less durable than other types of steel. Using large amounts of nickel and chromium also increases costs, as these two metals are much more expensive than iron.
18/8 is largely an older designation, and most steel producers now refer to this steel as 403 stainless steel, while cutlery manufacturers, the primary users of this steel grade, still use the older 18/8. Because of its chromium and nickel content, 18/8 steel cannot be heat-hardened, limiting its use to non-industrial applications, such as a material for cutlery and cookware.