Is a common material in the piercing industry, mainly due to the fact that it is relatively cheap, easy to obtain and also relatively easy to work with. It also has some drawbacks that make it less than ideal to use as initial jewelry when piercing. For example, stainless steel scratches very quickly and there is almost always nickel and chrome in it, both of which have the nasty property to irritate the skin.
There are many different types of stainless steel but only a few types have been tested and found to be suitable for wearing in the human body. Of those, ASTM F-138 is the most common in piercing jewellery. Other types of stainless steel are often sold as “surgical steel” but because this term has no official definition it is very unclear exactly what material you are dealing with. For example, it can happen that jewelry made with surgical steel will rust or leak nickel because some types of stainless steel leak nickel easily or have better corrosion resistance. Surgical steel is therefore also called “mystery steel” because you never know exactly what kind of stainless steel you are buying. Terms such as 316L, 304L etc. are standard codes for industrial purposes and not for implant grade materials so these materials are not made to be worn in the body.
With stainless steel jewelry, the surface finish is also extra important because a mirror polishing prevents nickel from “leaking”. Polishing jewelry is the most labour intensive part in the manufacturing process and is often not done to a mirror finish to keep the price low. An extra reason to be careful with cheap jewelry.