ASTM C692-00
(Test Method)Standard Test Method for Evaluating the Influence of Thermal Insulations on External Stress Corrosion Cracking Tendency of Austenitic Stainless Steel
Standard Test Method for Evaluating the Influence of Thermal Insulations on External Stress Corrosion Cracking Tendency of Austenitic Stainless Steel
SCOPE
1.1 This test method covers two procedures for the laboratory evaluation of thermal insulation materials that may actively contribute to external stress corrosion cracking (ESCC) of austenitic stainless steel due to soluble chlorides within the insulation. It should be understood that this laboratory procedure is not intended to cover all of the possible field conditions that might contribute to ESCC.
1.2 While the 1977 edition of this test method (Dana test) is applicable only to wicking-type insulations, the procedures in this edition are intended to be applicable to all insulating materials, including cements, some of which would disintegrate when tested in accordance with the 1977 edition. Wicking insulations are materials that wet through and through when partially (50 to 75%) immersed in water for a short period of time (10 min or less).
1.3 These procedures are intended primarily as a preproduction test for qualification of the basic chemical composition of a particular manufacturer's product and are not intended to be routine tests for ongoing quality assurance or production lot compliance. Test Methods C871, on the other hand, is used for confirmation of acceptable chemical properties of subsequent lots of insulation previously found acceptable by this test method.
1.4 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: C 692 – 00
Standard Test Method for
Evaluating the Influence of Thermal Insulations on External
Stress Corrosion Cracking Tendency of Austenitic Stainless
Steel
This standard is issued under the fixed designation C692; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope and Chromium-Nickel Stainless Steel Plate, Sheet, and
Strip for Pressure Vessels
1.1 This test method covers two procedures for the labora-
A370 TestMethodsandDefinitionsforMechanicalTesting
tory evaluation of thermal insulation materials that may ac-
of Steel Products
tively contribute to external stress corrosion cracking (ESCC)
C795 Specification for Thermal Insulation for Use in Con-
of austenitic stainless steel due to soluble chlorides within the
tact with Austenitic Stainless Steel
insulation. It should be understood that this laboratory proce-
C871 Test Methods for Chemical Analysis of Thermal
dureisnotintendedtocoverallofthepossiblefieldconditions
Insulation Materials for Leachable Chloride, Fluoride,
that might contribute to ESCC.
Silicate, and Sodium Ions
1.2 While the 1977 edition of this test method (Dana test) is
G30 Practice for Making and Using U-Bend Stress Corro-
applicable only to wicking-type insulations, the procedures in
sion Test Specimens
this edition are intended to be applicable to all insulating
materials, including cements, some of which would disinte-
3. Summary of Test Method
gratewhentestedinaccordancewiththe1977edition.Wicking
3.1 The procedures in this test method consist of using a
insulations are materials that wet through and through when
specimenofinsulationtoconductdistilled(ordeionized)water
partially (50 to 75%) immersed in water for a short period of
by wicking or dripping to an outside surface, through the
time (10 min or less).
insulation, to a hot inner surface of stressedType 304 stainless
1.3 Theseproceduresareintendedprimarilyasapreproduc-
steel for a period of 28 days. If leachable chlorides are present,
tion test for qualification of the basic chemical composition of
they are carried along with the water and concentrated at the
a particular manufacturer’s product and are not intended to be
hot surface by evaporation in much the same way as has been
routine tests for ongoing quality assurance or production lot
experienced in actual industrial process situations.
compliance.TestMethodsC871,ontheotherhand,isusedfor
3.2 Exposed stainless steel coupons are examined visually,
confirmation of acceptable chemical properties of subsequent
and under 103 to 303 magnification, if necessary, to detect
lots of insulation previously found acceptable by this test
ESCC after the prescribed period of exposure.
method.
1.4 The values stated in inch-pound units are to be regarded
4. Significance and Use
as the standard. The values given in parentheses are for
4.1 An inherent characteristic of some alloys of austenitic
information only.
stainless steel is their tendency to crack at stress points when
1.5 This standard does not purport to address all of the
exposedtocertaincorrosiveenvironments.Themechanismsof
safety concerns, if any, associated with its use. It is the
ESCC are complex and not completely understood but are
responsibility of the user of this standard to establish appro-
apparently related to certain metallurgical properties. Chloride
priate safety and health practices and determine the applica-
ions concentrated at a stress point will catalyze crack forma-
bility of regulatory limitations prior to use.
tion. It has been reported that other halide ions do not promote
2. Referenced Documents ESCC to the same degree as does chloride using the test
technology of Test Method C692 (drip test).
2.1 ASTM Standards:
A240/A240M Specification for Heat-Resisting Chromium
Annual Book of ASTM Standards, Vol 01.03.
1 3
This test method is under the jurisdiction of ASTM Committee C-16 on Annual Book of ASTM Standards, Vol 04.06.
Thermal Insulation and is the direct responsibility of Subcommittee C16.31 on Annual Book of ASTM Standards, Vol 03.02.
Chemical and Physical Properties. Private communication from authors of paper presented at Bal HarbourASTM
Current edition approved March 10, 2000. Published May 2000. Originally C-16SymposiumonDecember9,1987.Whitaker,T.E.,Whorlow,KennethM.,and
published as C692–71. Last previous edition C692–97. Hutto, Francis B., Jr., “New Developments in Test Technology for ASTM C692.”
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
C 692
4.2 Chlorides are common to many environments, so great 5.5 Cements with a clay binder may be tested by casting a
care shall be taken to protect austenitic stainless steel from 1 ⁄2-in. (38-mm) thick slab, drying, and using the drip proce-
chloride contamination. dure. Such a sample will disintegrate in the Dana test proce-
4.3 Most thermal insulations will not, of themselves, cause dure.
stress corrosion cracking as may be shown by tests. When 5.6 Thedripproceduremightalsobeextendedtothetesting
exposed to elevated-temperature (boiling point range), envi- of coatings applied to the coupon prior to test. The corrosive
ronments containing chlorides, moisture, and oxygen, how- liquidsdrippedintosuchasystemwouldbelimitedonlybythe
ever, insulation systems may act as collecting media, transmi- imagination of the researcher.
grating and concentrating chlorides on heated stainless steel
6. Apparatus for Dana Test Procedure
surfaces. If moisture is not present, the chloride salts cannot
migrate, and stress corrosion cracking because of chloride-
6.1 Enclosure—The test apparatus may be located in a
contaminated insulation cannot take place. cabinet or other closed structure provided with a blower to
4.4 Insulations may also be specially formulated to inhibit
maintain a positive internal pressure, and it may be equipped
stress corrosion cracking in the presence of chlorides through with a filter for intake air to minimize dust or other contami-
modifications in basic composition or incorporation of certain nation. The test apparatus may also be housed in any suitable
chemical additives.
clean environment not subject to chloride contamination. The
4.5 The ability of the 28-day test to measure the corrosion enclosure shall not be so tight as to exclude oxygen from the
potential of insulation materials is documented by Karnes,
system, since oxygen is necessary for ESCC to occur.
whose data appear to have been used for construction of the 6.2 Pyrex Glass Wool,
acceptability curve used in Specification C795 and other
6.3 “Cookie Cutter,” made from 1 ⁄4 in. (32 mm) thin wall
specifications. electrical conduit (inside diameter 1.38 in. (35 mm)) to cut a
4.6 Themetalforallofthecouponsusedinthistestmethod
1 ⁄8-in. (35-mm) diameter plug from 2-in. (51-mm) Pyrex
(C692) shall be qualified (see Section 13) to ascertain that Glass Wool.
under conditions of the test, chloride ions will cause the metal
6.4 Specimen Holder, as shown in Fig. 1, or equivalent.
to crack, and deionized water alone will not cause cracks. 6.5 Precision Bender, see Practice G30.
6.6 Wet-Grinding Belt Grinder, 80-grit.
5. Applicability (see also Section 10.2) 6.7 Copper Lugs, commercial 2/0–4/0 solderless, or 2 by ⁄2
by ⁄8 in. (51 by 13 by 3.2 mm) copper tabs.
5.1 While the original test procedure for the 1977 edition of
6.8 Silver Solder, and chloride-free flux for use with stain-
this test method (Dana Test) was limited to “wicking-type
less steel.
insulations,” the “drip test procedure” given in this edition can
6.9 Torch, acetylene or propane.
be used for all insulations that can be cut or formed into the
6.10 Bolt, stainless steel, ⁄16 in. (5 mm) in diameter and
required test specimen.
2 ⁄2-in. (65-mm) long with insulating washer and nut for
5.2 Heat treatment at some temperature (as recommended
electrically insulating the bolt from the U-bend specimen.
by the manufacturer) up to the maximum use temperature may
6.11 Hand-held Magnifier,103 or 303 binocular micro-
be necessary to make the insulating material “wick,” and thus
scope, or both.
testablebyeitherinsulationtestprocedure(seeSections11and
6.12 Band Saw.
12).
6.13 Hole Saw, 2-in. (51-mm) outside diameter (optional).
5.3 If the test insulation cannot be made to wick in any way
6.14 Crystallizing Dish, of borosilicate glass, 7 ⁄2in. (190
(such as in the case of organic or inorganic closed-cell foams),
mm) in diameter by 4 in. (100 mm) in depth, or stainless steel
or when a component of the insulation (such as an attached
1 1
pan 9 ⁄2 by 5 ⁄2 by 4 in. (41 by 140 by 102 mm) deep.
exterior jacket material) would be heated beyond the manufac-
6.15 Electrical Transformer, isolation-type. (approximately
tures recommended temperature for the exterior component,
1 150 mV/150 AMP).
thenthe1 ⁄2-in.(38-mm)widetestspecimenmaybeslicedinto
6.16 Thermocouple, 28 gage or smaller.
two ⁄4-in. (19-mm) thick segments. When the two halves are
6.17 Epoxy Adhesive, aluminum filled, (Metalset A4 or
held together with wire, pins, or a rubber band, they may be
equivalent).
tested by dripping into the crack between the two halves, thus
6.18 Drill Bit, ⁄32-in. (7-mm), cobalt steel preferred.
simulating the situation where water penetrates the junction
6.19 Dye Penetrant and Developer, available at most weld-
between two sections of insulation. It may be necessary to wet
ing supply houses.
the mating faces on the two half sections in order to make
water wick down to the coupon surface.
7. Apparatus for Drip Test Procedure
5.4 Adhesives can be tested by gluing together a test block
7.1 Steam Heated Pipe—A 5-ft (1.5-m) section of 1 ⁄2 in.
of the insulation material to be used with the adhesive. The
IPS pipe (inconel or other corrosion-resistant material is
adhesive joint must come into contact with the stainless steel
recommended) is suggested, heated either by a small selfcon-
test coupon.
tained steam boiler or by regulated house steam.
6 7
Karnes,H.F.,“TheCorrosionPotentialofWettedThermalInsulation,”AICHE, Available from lab supply houses.
57th National Meeting, Minneapolis, MN, September 26 through 29, 1965. Available from Smooth-On, Inc., 1000 Valley Road, Gillette, NJ 07933.
C 692
FIG. 1 Suction Cup Coupon Holder
7.2 Peristaltic Pump—A multichannel peristaltic pump is
recommended to supply 250 (625) mL/day to each specimen.
7.3 I.V. Bottles, 1 L or equivalent, to individually supply
each test specimen with test liquid.
FIG. 2 Typical External Stress Corrosion Cracks (53
7.4 Specimen Holder, for grinding. See Fig. 1.
Magnification)
7.5 Precision Bender, see Fig. 2 in the 1979 edition of
Practice G30.
7.6 Wet-Sanding Belt Sander, with 80 grit belt.
the coupon temperatures “lag” the furnace temperature by at
7.7 Bolt, stainless steel, ⁄16 in. (5 mm) in diameter by
least 50 to 100°F (28 to 56°C).
2 ⁄2-in. (65-mm) long with nut.
9.4 Asuggestion for sensitizing in an inert atmosphere is to
7.8 Hole Saw, 2-in. (51-mm) outside diameter.
useastainlesssteelboxwithatight-fittingcovertocontainthe
7.9 Band Saw.
argon around the coupons during sensitization.
7.10 Thermocouple, 28 gage or smaller.
9.5 Grip coupon with suction cup holder (see Fig. 1) or
7.11 Heat Transfer Grease, chloride free.
othermeanstofacilitatewetgrindingonan80-gritbeltgrinder.
7.12 Kimwipe Tissue, chloride free.
Grind parallel to the long dimension of the coupon using an
80-grit wet belt with just enough pressure to remove the dull
8. Reagents and Materials
finish and leave the metal bright. Do not overgrind. The
8.1 Distilled or Deionized Water, containing less than 0.1
beltground face is the test surface to be exposed to the thermal
ppm chloride ions.
insulation. The test area is the bent coupon surface which
8.2 Distilled or Deionized Water, containing 1500 ppm
actually comes into contact with the insulation.
chloride ion (2.473 g NaCl/L).
9.6 Smooth and round sheared edges to prevent accidental
8.3 Type 304 Stainless Steel Sheet— 16 gage, meeting the
cutting of fingers.
composition requirements of Specification A240. Certificates
9.7 Bend each ground coupon to a 1.00 6 0.01-in. (25.4 6
of chemical composition and mechanical properties, including
0.25-mm) outside radius using a roll bender as shown in Fig. 5
ultimate tensile strength and yield strength by the 0.2% offset
of the 1979 edition of Practice G30 to produce a U-shape in
method are required. Type 304 stainless steel meeting Speci-
which the “legs” are parallel to within ⁄16 in. (1.6 mm).
fication A240 shall have a carbon content in the range of
9.8 Drill or punch a ⁄32-in. (7-mm) hole in each end using
0.05–0.06% and shall be solution-annealed.
the special jig shown in Fig. 3.The use of cobalt steel drill bits
is highly recommended on 304 stainless steel as other bits dull
9. Test Coupons
quickly.
9.1 Shear 2 by 7-in. (51 by 178-mm) coupons from 16-gage
Type 304 stainless sheet, as specified in 8.3, with the long
dimension parallel to the long dimension of the sheet. (Long
dimension parallel to sheet-rolling direction.)
9.2 Clean coupons with chloride-free liquid soap and water
to remove any grease or other contamination.
9.3 Sensitize all coupons before bending by heating at
1200°F (649°C) in an argon (inert) or air (oxidizing) atmo-
sphere for three hours. Let cool in the furnace after the
sensitizing period. Temperature of the coupons must be
measured in the stack of coupons, not in the furnace itself, as
Kimwipe is a trademarked product of Kimberly-Clark Corp., Roswell, GA.
Foradiscussionoftheeffectofsensitizingstainlesssteelanditssusceptibility
to stress corrosion, refer to “Stress-Corrosion Cracking of Sensitized Stainless Steel
in Oxygenated High Temperature Water,” Batelle Columbus Laboratories, Report
FIG. 3 Jig for Positioning Holes in the U-Bend Specimen
No. BMI 1927, June 1972.
C 692
9.9 FortheDanatestonly,silver-soldera2/0–4/0solderless
copper electrical connector to each leg with the hole in the
connector centered on the drilled hole. While it has been
conventional to solder one lug to an inside surface and the
second to an outside surface, it is acceptable to solder both to
outside surfaces for greater convenience. The body of the
coupon should be shielded from high soldering temperatures
by placing a soaking-wet chloride-free cellulose pad on the
coupon next to the weld area to act as a heat sink. Carefully
remove all flux from
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