This article is from the Piercing FAQ, by Anne Greenblatt with numerous contributions by others.
2A.1a Report on Stainless Steel
by Sean Christian
Anatometal Inc. Body Jewelry, Santa Cruz, California
Presented at the Association of Professional Piercers Open Meeting
Edited by Anne Greenblatt
Surgical Stainless Steel: The term “surgical stainless steel” is not a
technical term. It is a term that was originally coined by knife and
cookware manufactures. It brought more marketable value to the
material that they used. “Surgical stainless steel” is a generic term
for a variety of different grades of steel and is not commonly found
in any medical or metallurgical reports. There are no standards set
for this type of metal.
Implant Grade Stainless Steel: “Implant grade stainless steel” is a
more accurate term for the steel used in body jewelry. There are
standards set for what materials can be called implant grade. There
are currently only two different types of stainless steel that
commonly match these standards: 316L and 316LVM. These materials have
been employed successfully in human implants that are in contact with
soft tissue and bone for more than a decade.
316L and 316LVM: Designations for types of steel that meet the
standards for “implant grade.” 316 is the designation number. The “L”
in these two designations stands for low carbon. The “VM” stands for
vacuum melted. Both of these materials meet the ASTM designation F138 for “Implant Grade Stainless steel” and the ISO standard 5832-1 and 6892 for “Surgical Implant Material” and “Requirements Against Nickel Allergies.”
The ASTM and ISO
American Society of Testing and Materials: The ASTM is a
non-governmental organization that compiles information and makes
standards for manufacturing, materials, and methods for just about
everything. These standards are considered to be of the highest
International Organization for Standards: The ISO (which is not an
acronym, it is short for the Greek word isos meaning equal) is the
European equivalent of the ASTM. The ISO is trying to standardize all
European trade and manufacturing methods.
ASTM “F” Series: The “F” series of the ASTM designations concern
“medical grade materials” and are the guidelines for FDA approval of
materials used in medical products. Responsible manufactures of any
medical product comply with these standards.
ASTM F138 Grade 1 & 2: F138 is the designation number for the
“Standard Specification for Stainless Steel Bar and Wire for Surgical
Implants.” This standard characterizes composition and properties to
insure consistency for medical implant devices. 316L adheres to grade
1 and 316LVM adheres to grades 1 and 2. Implant Grade Stainless Steel
is chemically inert and atraumatic to the body so as not to react with
the surrounding tissues or the immune system.
The milling of stainless steel wire used in captive bead rings (not to
be confused with bar stock that is used in barbells) work-hardens the
wire to a point that it loses some of its corrosion resistance
properties. It requires these properties to be considered implant
Annealing is a process of heat treating metal. It involves heating
steel to about one half of its melting point and cooling it in a
controlled environment. Annealing stainless steel serves to produce
changes in the physical condition, mechanical properties and residual
stress levels of the metal. Specifically, the annealing process serves
to reduce the corrosive tendencies of the work-hardened metal. During
annealing, chromium carbides, which markedly decrease resistance to
inter-granular corrosion, are dissolved. Annealing literally cleans
up the metal.
We all know that annealed jewelry is easier to work with, and what we
need to understand is that non-annealed jewelry might not be safe to
use in piercings.
There are purposes for polishing the surface of bead rings other than
aesthetics. A mirror finish is required for implant devices; the metal
cannot be gray, blurred, or dull. When finished properly, stainless
steel is resistant to degradation by the body’s internal
environment. Having a mirror finish will improve impact strength,
decrease corrosion, and produce a non-porous surface that will not
Individuals do not have problems with the material content. Rather,
they have problems if the material is not finished properly and breaks
apart due to wear, fatigue, and material fragment build ups. The
surface of the metal must be free of any nicks, scratches, or burrs
that increase surface area and allow for bacterial colonization which
interferes with the body’s healing process.