| Most high end wrist watches
like emphasizing their watch bracelet and watch case are made
of 316L, 904L or Surgical Grade Stainless Steel. What are they?
Stainless Steel is not a single material but the name
for a family of corrosion resistant steels.
Properties of Stainless Steels
The advantageous properties of stainless steel can be seen
when compared to standard plain carbon mild steel. Although
stainless steels have a broad range of properties, in general,
when compared with carbon mild steel, stainless steels have:
- Higher corrosion resistance
- Higher cryogenic toughness
- Higher work hardening rate
- Higher hot strength
- Higher ductility
- Higher strength and hardness
- A more attractive appearance
- Lower maintenance
Corrosion Resistance of Stainless
Steel
All stainless steel are iron-based alloys that contain
a minimum of around 10.5% Chromium. The Chromium in the
alloy forms a self-healing protective clear oxide layer. This
oxide layer gives stainless steel their corrosion resistance.
The self healing nature of the oxide layer means the corrosion
resistance remains intact regardless of fabrication methods.
Even if the material surface is cut or damaged, it will self
heal and corrosion resistance will be maintained.
Conversely, normal carbon steels may be protected from corrosion
by painting or other coatings like galvanizing. Any modification
of the surface exposes the underlying steel and corrosion
can occur.
The corrosion of different grades of stainless steel will
differ with various environments. Suitable grades will depend
upon the service environment. Even trace amounts of some elements
can markedly alter the corrosion resistance. Chlorides in
particular can have an adverse effect on the corrosion resistance
of stainless steel.
Grades high in Chromium, Molybdenum and Nickel are the most
resistant to corrosion.
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