Type2205
Type2205
Type2205
Applications
Pressure vessels, tanks, piping, and heat Table 1. Composition, wt. pct.
exchangers in the chemical processing
industry 2205 Code ASTM ASTM
Piping, tubing, and heat exchangers Element Plus Two® S32205 S31803
for the handling of gas and oil Carbon 0.020 0.030 max 0.030 max
Effluent scrubbing systems Chromium 22.1 22.0–23.0 21.0–23.0
Pulp and paper industry digesters, bleaching Nickel 5.6 4.5–6.5 4.5–6.5
equipment, stock-handling systems Molybdenum 3.1 3.0–3.5 2.5–3.5
Rotors, fans, shafts, and press rolls requiring Nitrogen 0.18 0.14–0.20 0.08–0.20
combined strength and corrosion resistance Phosphorus 0.025 0.035 max 0.035 max
Cargo tanks for ships and trucks Manganese 1.45 2.00 max 2.00 max
Food processing equipment Sulfur 0.001 0.020 max 0.020 max
Silicon 0.45 1.00 max 1.00 max
General Characteristics Iron Balance Balance Balance
AvestaPolarit 2205 Code Plus Two® duplex
stainless steel combines excellent resistance to
pitting, crevice corrosion, and chloride stress
corrosion with high strength. Duplex stainless
steels typically have 50 to 60% austenite that
has formed in a ferritic matrix, as shown
Type 2205 Code Plus Two® 2
in the photo below (austenite is the lighter steel. Both S31803 and S32205 are included in
etched phase). the ASTM product specifications.
The trademark Code Plus Two® indicates
the commitment made several years ago not Structure
only to meet the requirements for S31803 as In the solution annealed condition from about
established in ASTM and ASME, but also to 1925°F, 2205 Code Plus Two® duplex stainless
meet two additional requirements. The first steel has a microstructure with about 40 to
requirement was that nitrogen should be in 50% ferrite. Grain size (expressed as a
the 0.14 to 0.20% range to gain its benefits in lamellar spacing) is fine, usually about
higher strength, higher corrosion resistance, 2–4 x 10-4 inch (5–10 µm), depending on
greater metallurgical stability, and superior product form.
properties after welding. The second At high temperatures, above 2000°F,
requirement was that all material should the steel will become increasingly ferritic,
pass a test for the absence of detrimental becoming fully ferritic at temperatures just
intermetallic phases. The tests developed by below the melting point. Higher nitrogen
AvestaPolarit for this purpose have been increases the temperature at which austenite
formalized as the ASTM A 923 standard test is stable within the duplex structure, thereby
method. facilitating the formation of austenite
These special requirements now define a subsequent to a high temperature exposure
new quality of 2205, designated S32205,
which is included in A 240 and A 480. S32205 Table 3. Mechanical Properties at Room Temperature
is dual certifiable as S31803, but represents ASTM A 240 Typical
what the users have come to expect of 2205
Yield Strength (0.2%), ksi 65 min. 74
Tensile Strength, ksi 90 min. 105
Table 2. Characteristic Temperatures Elongation, % 25 min. 30
Temperature °F Hardness HB 293 max. 256
Table 6. Lowest Temperature (°F) at Which the Corrosion Rate Exceeds 5 mpy
0.2% Hydrochloric Acid >Boiling >Boiling >Boiling >Boiling >Boiling >Boiling >Boiling >Boiling
1% Hydrochloric Acid 203 158 122 86 86p >Boiling 185 131
10% Sulfuric Acid 158 140 140 122 — 167 140 149
60% Sulfuric Acid 104 104 185 <54 — <57 <59 <<55
96% Sulfuric Acid 86 68 95 113 — 86 77 59
85% Phosphoric Acid 194 230 248 203 176 203 194 203
10% Nitric Acid >Boiling >Boiling >Boiling >Boiling >Boiling >Boiling >Boiling >Boiling
65% Nitric Acid 221 212 212 212 212 230 221 203
80% Acetic Acid >Boiling >Boiling >Boiling >Boiling 212p >Boiling >Boiling >Boiling
50% Formic Acid 158 212 212p 104 ≤50 194 194 59
50% Sodium Hydroxide 275 239 Boiling 194 185 230 194 203
83% Phosphoric Acid + 2% Hydrofluoric Acid 185 194 248 149 113 140 122 95
60% Nitric Acid + 2% Hydrochloric Acid >140 140 >140 >140 >140 >140 >140 >140
50% Acetic Acid + 50% Acetic Anhydride >Boiling >Boiling >Boiling 248 >Boiling 230 212 194
1% Hydrochloric Acid + 0.3% Ferric Chloride >Boiling, p 203ps 140ps 77p 68p 203ps 113ps 68p
10% Sulfuric Acid + 2000ppm Cl- + N2 149 104 131 77 — 122 95 <55
10% Sulfuric Acid + 2000ppm Cl- + SO2 167 140 122 <<59p — 104 <59 <<50
WPA1, High Cl- Content 203 176 122 ≤50 <<50 203 113 86
WPA2, High F- Content 176 140 95 ≤50 <<50 167 140 95
ps = pitting can occur WPA P2O5 Cl- F- H2SO4 Fe2O3 Al2O3 SiO2 CaO MgO
ps = pitting/crevice corrosion can occur
1 54 0.20 0.50 4.0 0.30 0.20 0.10 0.20 0.70
2 54 0.02 2.0 4.0 0.30 0.20 0.10 0.20 0.70
316L °F
(2.5 min Mo)
176 176
2205
904L
140 140
316
(2.5 min Mo)
104 104
68 68
0 20 40 60 0 10 20 30
H2SO4’ %
H2SO4 %
’
5 Type 2205 Code Plus Two®
Table 7. General Corrosion in Wet Process Figure 4. Critical Pitting Temperature in 1M NaCI
Phosphoric Acids Measured using the AvestaPolarit Pitting Cell
Corrosion Rate, ipy
Grade Solution A, 140°F Solution B, 120°F
2205 Code
2205 Code Plus Two®
Plus Two® 3.1 3.9
904L
316L >200 >200
904L 47 6.3
316L
Composition, wt % (2.5 Mo)
P2O5 HCl HF H2SO4 Fe2O3 Al2O3 SiO2 CaO MgO
Sol A 54.0 0.06 1.1 4.1 0.27 0.17 0.10 0.20 0.70 SAF 2304®
Sol B 27.5 0.34 1.3 1.72 0.4 0.01 0.3 0.02 —
316L
concentrations and temperatures, but will not
perform as well as 904L. With chloride conta-
mination, the corrosion resistance of all of 304
these stainless steels is reduced, but the high
chromium and molybdenum contents of 0 20 40 60 80 100 120 140
Temperature °F
2205 give performance equal to 904L.
The advantage of 2205 in a complex,
mildly-reducing acid with many minor (CCT) in 10% ferric chloride (6% FeCl3 or 10%
chemical species is illustrated with two FeCl3 • 6H20). As shown in Figure 5, the
phosphoric acid solutions in Table 7. Because crevice corrosion resistance of AvestaPolarit
2205 is substantially better than either Type 2205 Code Plus Two exceeds that of grades
316L or 904L in this situation, it is a good often specified for moderate chloride service
candidate for wet process phosphoric such as Type 316L, Type 317L, and 904L.
applications. In service, 2205 Code Plus Two duplex
stainless steel has been resistant to pitting
Pitting and Crevice Corrosion
The chromium, molybdenum, and nitrogen in Figure 5. Critical Crevice Corrosion Temperature (CCT)
2205 Code Plus Two also provide excellent In 10% FeCl3•6H20
resistance to pitting and crevice corrosion.
There are many different ways to characterize 2205 Code
resistance to pitting attack, but one of the Plus Two®
newest and most effective is determination of
the critical pitting temperature (CPT) using 316L
the electrochemical methods developed by
AvestaPolarit and adopted as ASTM G 150. It 317L
is extremely accurate and able to detect even
the small differences of within-grade 317LMN
variations. As shown in Figure 4, the pitting
resistance of 2205 Code Plus Two® is closely
904L
comparable to that of the highly alloyed 904L
(20 Cr - 25 Ni - 4.5 Mo) and clearly superior
to that of 316L. 254 SMO®
Another commonly applied comparison
test is ASTM G 48, Practice B, the 0 20 40 60 80 100 120
Temperature °F
determination of critical crevice temperature
Type 2205 Code Plus Two® 6
attack by seawater on smooth, clean surfaces This reaction is slow enough that it is
at ambient conditions, but is not resistant to detected only after long service in this
crevice corrosion when tight crevices are temperature range, and not by exposures
imposed on the surface. Accordingly, 2205 during fabrication. So its effect is avoided by
may be considered for seawater applications the prohibition of the use of duplex stainless
when economy is important and regular steels in the temperature range.
maintenance is possible, but it would not be a
good choice for critical applications or where Chloride Stress Corrosion Cracking (SCC)
regular maintenance would be difficult. Chloride stress corrosion cracking of
austenitic stainless steels can occur when the
Sensitization by Thermal Exposure necessary conditions of temperature, tensile
The very low carbon content of 2205 Code stress, oxygen, and chlorides are present.
Plus Two in combination with its generally Because these conditions are not easily
very good corrosion resistance make the steel controlled and are often characteristic of the
essentially immune to intergranular corrosion operating environment, SCC has sometimes
caused by chromium carbide precipitation. been a barrier to the use of stainless steels.
The test practices of ASTM A 262 were Types 304L and 316L are especially
designed for austenitic stainless steels and do susceptible to SCC, and even Type 317L is
not necessarily give meaningful results when not resistant. However, the duplex nature of
strictly applied to duplex stainless steels such 2205 imparts an excellent resistance to SCC.
as 2205, especially with regard to the issue of As shown in Table 8, 2205 resists SCC in two
a sensitizing treatment prior to testing. sodium chloride-containing environments
The duplex stainless steels are susceptible that provide meaningful results relating to
to loss exposures leading to precipitation of many practical service conditions. As with
phases other than chromium carbide. When most austenitic stainless steels, 2205 duplex
the nitrogen content is too low, retarding the stainless steel will not resist boiling 42%
formation of austenite at high temperatures magnesium chloride, but this environment is
after welding, there is a risk of formation of rarely encountered in service. The boiling
chromium nitride in the ferrite. As further magnesium chloride test results indicate only
discussed elsewhere, exposure of a duplex that 2205 can be susceptible to SCC in certain
stainless steel to temperatures in the range of specific environments.
1100 to 1825°F can cause precipitation of
intermetallic phases with substantial loss of Sulfide Stress Corrosion Cracking (SSC)
corrosion resistance. These precipitates are The presence of hydrogen sulfide in a
better detected by tests for critical pitting chloride solution often will increase its stress
temperature or critical crevice temperature in corrosion–promoting capability, resulting in
strong chloride environments, and not by
the ASTM A 262 tests commonly used for Table 8. Stress Corrosion Cracking Resistance
sensitization to intergranular corrosion. Boiling Wick Boiling
ASTM A 923 was designed to detect the Grade 42% MgCI2 Test 25% NaCI
precipitation of intermetallic phases in duplex
2205 Code Plus Two® F P P
stainless steels and should be specified as a
254 SMO® F P P
requirement for all 2205 mill products.
Type 316L F F F
Very long exposure to temperatures in the Type 317L F F F
650 to 980°F range may lead to a loss of Alloy 904L F P or F P or F
toughness resulting from precipitation of Alloy 20 F P P
alpha prime phase of ferrite of the duplex.
(P = PASS, F = FAIL)
7 Type 2205 Code Plus Two®
Figure 6. Corrosion Fatigue in Synthetic Seawater A test commonly used to rate materials
for SSC resistance is NACE Standard Test
Stress Amplitude, ksi Method TM0177. It uses a chloride–acetic
acid solution saturated with hydrogen
sulfide. In this test, uniaxially loaded 2205
73
mill-annealed specimens have withstood 500
hours without cracking at an applied stress
58 of 1.3 times the 0.2% offset yield stress. The
performance of welds will depend on the
44 weld microstructure and filler metal.
2205 is included in NACE MR0175
29
(Sulfide Stress Cracking Resistant Metallic
2205 Materials for Oil Field Equipment).
3RE60 Solution-annealed 2205 and cold worked
15 316L 2205 are acceptable for use at any tempera-
(2.5 min Mo)
ture up to 450°F (232°C) in sour environments
0 if the partial pressure of hydrogen sulfide
105 106 107 does not exceed 0.3 psi (20 mbar), the yield
Number of cycles to failure strength of the material is no greater than 160
ksi (1100 MPa), and if its hardness is not
Smooth rotating bent beam at 1500 rpm (0.6-inch plate) greater than 36 HRC.
Corrosion Fatigue
what is known as hydrogen or sulfide stress There are many applications in which
cracking (SSC). Materials that have high processing equipment is subject to both an
strength and contain martensite or ferrite aggressively corrosive environment and to
would generally be susceptible to cracking at cyclic loading. Examples may include
lower temperatures and chloride levels than vibratory bulk handling equipment, press
they would in the absence of hydrogen rolls, and motor mounts. The corrosive
sulfide. The resistance of duplex stainless environment may significantly reduce
steels is a complex function of microstructure, the effective fatigue strength of a steel.
stress, and the environment. Austenite favors AvestaPolarit 2205 Code Plus Two combines
resistance and 2205 is usually superior to the high strength and high corrosion resistance
martensitic and ferritic stainless steels. For a to produce high corrosion fatigue strength.
given environment, performance is also a As shown in Figure 6, the S-N curve for
function of some fraction of the strength; AvestaPolarit 2205 shows its superiority to
therefore, 2205 may compare favorably with Type 316L and to 3RE60 (a duplex stainless
some lower-strength austenitic stainless steel with 18% Cr and 2.8% Mo) in synthetic
steels, depending on the chloride seawater testing.
concentrations and temperature. Examples
of environments which contain hydrogen Fabrication
sulfide include sour oil and gas wells, and Design
refinery condensates. 2205 has been AvestaPolarit 2205 Code Plus Two is a strong,
successfully used in sour environments; tough stainless steel. As shown in Table 9,
however, before using any material in such the ASME Boiler and Pressure Vessel Code
environments, a performance analysis should allows use of 2205 up to 600°F with
be undertaken. outstanding strength levels. In many
Type 2205 Code Plus Two® 8
Table 9. Maximum Allowable Stress Values, ASME becomes substantially stronger than the
Boiler and Pressure Vessel Code, Section VIII,
Division 1, 1999 Addenda, 3.5 Safety Factor
ferrite and may cause cracking, a particular
danger to “cold” edges. Below 1700°F there
Stress, ksi
can be rapid formation of intermetallic phases
Grade -20 to 100°F 300°F 400°F 500°F 600°F
because of the combination of temperature
2205 Code and deformation. Whenever hot forming is
Plus Two® 25.7 24.8 23.9 23.3 23.1 done, it should be followed by a full solution
316L 16.7 16.7 15.7 14.8 14.0 anneal at 1900°F minimum and rapid quench
904L 20.3 15.1 13.8 12.7 11.9 to restore phase balance, toughness, and
Alloy G 23.3 23.3 23.3 23.3 22.7
corrosion resistance. Stress relieving is not
required or recommended; however, if it
must be performed, the material should
constructions it is possible to use this strength receive a full solution anneal at 1900°F
for greater economy by downgauging from minimum, followed by rapid cooling or
the heavier sections that would be required water quenching.
with Type 316L or Alloy 904L. 2205 should
not be used above 600°F so that formation Heat Treatment
of undesirable phases that may reduce AvestaPolarit 2205 Code Plus Two should
corrosion resistance and toughness may be be annealed at 1900°F minimum, followed
avoided. However, 2205 Code Plus Two steel by rapid cooling, ideally by water quenching.
can be used indefinitely at the moderate This treatment applies to both solution
temperatures typically encountered in annealing and stress relieving. Stress relief
chemical processing and heat exchanger treatments at any lower temperature carry
service. the risk of precipitation of detrimental
intermetallic or nonmetallic phases.
Cold Forming
AvestaPolarit 2205 Code Plus Two is readily
sheared and cold formed on equipment
Figure 7. Mechanical Properties of 2205 after
suited to working stainless steels. However,
Cold Working
because of the high strength and rapid work
hardening of 2205, forces substantially Stress Amplitude, ksi
higher than those for austenitic steels are 145
Elongation, %
AvestaPolarit, Inc.
425 North Martingale Road, Suite 2000
Schaumburg, IL 60173-2218
www.avestapolarit-na.com
1.800.833.8703