If a 300 series stainless steel component is under
tensile stress, either because of operation or residual stresses left
during manufacture, chloride induced pitting will deepen even more.
Since the piece is under tensile stress cracking will occur in the
stressed piece. Usually there will be more than one crack present
causing the pattern to resemble a spider's web.
Chloride stress cracking is a serious problem in
industry and not often recognized by the people involved. In the seal
business it is a serious problem if you use stainless steel springs
or stainless steel bellows in your seals. This is the main reason
that Hastelloy C is recommended for spring material. Here are some
additional thoughts about chloride stress cracking that you'll want
- Chlorides are the big problem when using the
300 series grades of stainless steel. The 300 series is the one
most commonly used in the process industry because of its good
corrosion resistant proprieties. Outside of water, chloride is the
most common chemical found in nature and remember that the most
common water treatment is the addition of chlorine.
- Beware of insulating or painting stainless
steel pipe. Most insulation contains chlorides and piping is
frequently under tensile stress. The worst condition would be
insulated, steam traced, stainless steel piping.
If it's necessary to insulate stainless steel
pipe, a special chloride free insulation can be purchased, or the
pipe can be coated with a protective film prior to
- Stress cracking can be minimized by annealing
the metal after manufacture, to remove residual manufactured
- Never replace a carbon steel bolt with a
stainless steel one unless you're sure there are no chlorides
present. Bolts can be subject to severe tensile
- No one knows the threshold values for stress
cracking to occur. We only know that you need tensile stress,
chlorides, temperature and the 300 series of stainless steel. We
do not know how much chloride, stress or temperature.
- Until I figured out what was happening I had
trouble breaking stainless steel fishing hooks in the warm water
where I live in Florida.
- Many cleaning solutions and solvents contain
chlorinated hydrocarbons. Be careful using them on or near
stainless steel. Sodium hypochlorite, chlorethene. methylene
chloride and trichlorethane are just a few in common use. The most
common cleaner used with dye checking material is trichloroethane,
explaining the reason we sometimes experience cracks after we weld
stainless steel and dye check it to inspect the quality of the
- There is evidence that the rate of chloride
stress corrosion slows down below 40 F (5° C). and above 285
F (140° C) and.
- problems with the 300 series of stainless
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