Type 316/316L
Stainless Steel
Type 316 Stainless Steel is an
excellent material for use with
most organic systems. A few
organic acids and organic halides
can, under certain conditions,
hydrolyze to form inorganic
halogen acids which will attack
T316SS. Acetic, formic and other
organic acids are routinely han-
dled in T316SS. T316SS is not
normally the material of choice
for inorganic acid systems. At
ambient temperatures it does
offer useful resistance to dilute
sulfuric, sulfurous, phosphoric
and nitric acids, but sulfuric,
phosphoric and nitric acids
readily attack T316SS at elevated
temperatures and pressures.
Halogen acids attack all forms of
stainless steel rapidly, even at
low temperatures and in dilute
solutions.
Although T316SS offers
excellent resistance to surface
corrosion by caustics, they can
cause stress corrosion cracking
in stainless pressure vessels. This
phenomenon begins to appear at
temperatures just above 100 °C
and has been the most common
cause of corrosion failure in stain-
less laboratory vessels. T316SS
does offer good resistance to
ammonia and to most ammonia
compounds.
Halogen salts can cause severe
pitting in all stainless steels.
Chlorides can cause stress corro-
sion cracking, but many other salt
solutions can be handled in stain-
less vessels, particularly neutral
or alkaline salts.
At moderate temperatures
and pressures, T316SS can be
used with most commercial
gases. In scrupulously anhydrous
systems even hydrogen chloride,
hydrogen fluoride and chlorine
can be used in stainless steel.
Essentially all of the T316SS
produced today also meets the
specifications for T316L, low
carbon stainless steel.
All Parr raw
materials are
carefully identified
throughout the
manufacturing
process for
traceability —
as required by
ASME and
other codes.
Alloy 20
Alloy 20 is an enriched grade
of stainless steel, designed
specifically for use with dilute (up
to 30 percent by weight) sulfuric
acid at elevated temperatures.
It can also be used for nitric
and phosphoric acid systems as
well as for all systems for which
T316SS is suitable.
Alloy 400
Alloy 400 is an alloy com-
prised essentially of two-thirds
nickel and one-third copper. For
many applications it offers about
the same corrosion resistance
as nickel, but with higher
maximum working pressures and
temperatures and at a lower cost
because of its greatly improved
machinability.
Alloy 400 is widely used for
caustic solutions because it is
not subject to stress corrosion
cracking in most applications.
Chloride salts do not cause stress
corrosion cracking in Alloy 400.
It is also an excellent material for
fluorine, hydrogen fluoride and
hydrofluoric acid systems. Alloy
400 offers some resistance to
hydrochloric and sulfuric acids
at modest temperatures and
concentrations, but it is seldom
the material of choice for these
acids. As would be expected from
its high copper content, Alloy 400
is rapidly attacked by nitric acid
and ammonia systems.
Alloy 600
Alloy 600 is a high nickel alloy
offering excellent resistance to
caustics and chlorides at high
temperatures and high pressures
when sulfur compounds are
present. In caustic environments,
Alloy 600 is unexcelled. It also is
often chosen for its high strength
at elevated temperatures.
Although it can be recommended
for a broad range of corrosive
conditions, its cost often limits
its use to only those applications
where its exceptional characteris-
tics are required.
Table I
Nominal Chemical Composition of Pressure Vessel Materials
Major Elements (Percent)
Material
Typical Trade Name Fe Ni
Cr
Mo Mn Other
T316 Stainless Steel
65 12 17 2.5 2.0 Si 1.0
Alloy 20
Carpenter 20
35 34 20 2.5 2.0 Cu 3.5, Cb 1.0 max
Alloy 400
Monel 400
1.2 66
Cu 31.5
Alloy 600
Inconel 600
8
76 15.5
Alloy B-2
Hastelloy B-2
2
66 1
28 1
Co 1.0
Alloy C-276
Hastelloy C-276
6.5 53 15.5 16 1
W4.0, Co 2.5
Nickel 200
99
Titanium Grade 2
Commercially pure titanium
Ti 99 min
Titanium Grade 4
Commercially pure titanium
Ti 99 min
Titanium Grade 7
99
0.15 Pd
Zirconium Grade 702
Zr + Hf 99.2 min, Hf 4.5 max
Zirconium Grade 705
Zr + Hf 95.5 min, Hf 4.5 max, Nb 2.5
1
11
P a r r I n s t r u m e n t C o m p a n y
1 - 8 0 0 - 8 7 2 - 7 7 2 0
D e s i g n F e a t u r e s
