ASTM C692-13(2018)

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C692 − 13 C692 − 13 (Reapproved 2018)
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. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers two procedures for the laboratory evaluation of thermal insulation materials to determine whether
they contribute to external stress corrosion cracking (ESCC) of austenitic stainless steel due to soluble chlorides within the
insulation. This laboratory procedure is not intended to cover all of the possible field conditions that 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 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 standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
A240/A240M Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and
for General Applications
A370 Test Methods and Definitions for Mechanical Testing of Steel Products
C168 Terminology Relating to Thermal Insulation
C795 Specification for Thermal Insulation for Use in Contact with Austenitic Stainless Steel
C871 Test Methods for Chemical Analysis of Thermal Insulation Materials for Leachable Chloride, Fluoride, Silicate, and
Sodium Ions
G30 Practice for Making and Using U-Bend Stress-Corrosion Test Specimens
3. Terminology
3.1 Definitions: Refer to Terminology C168 for definitions relating to insulation.
This test method is under the jurisdiction of ASTM Committee C16 on Thermal Insulation and is the direct responsibility of Subcommittee C16.31 on Chemical and
Physical Properties.
Current edition approved May 1, 2013Nov. 1, 2018. Published May 2013December 2018. Originally approved in 1971. Last previous edition approved 20082013 as
ε1
C692 – 08C692 – 13. . DOI: 10.1520/C0692-13.10.1520/C0692-13R18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C692 − 13 (2018)
4. Summary of Test Method
4.1 The procedures in this test method consist of using a specimen of insulation to conduct distilled (or deionized) water by
wicking or dripping to an outside surface, through the insulation, to a hot inner surface of stressed Type 304 stainless steel for a
period of 28 days. If leachable chlorides are present, they are carried along with the water and concentrated at the hot surface by
evaporation in much the same way as has been experienced in actual industrial process situations.
4.2 Exposed stainless steel coupons are examined visually, and under 10 to 30× magnification, if necessary, to detect ESCC after
the prescribed period of exposure.
5. Significance and Use
5.1 An inherent characteristic of some alloys of austenitic stainless steel is their tendency to crack at stress points when exposed
to certain corrosive environments. The mechanisms of ESCC are complex and not completely understood but are apparently related
to certain metallurgical properties. Chloride and fluoride ions have the potential to induce stress corrosion cracking in the absence
of inhibiting ions.
5.2 Chlorides are common to many environments, so great care shall be taken to protect austenitic stainless steel from chloride
contamination.
5.3 Most thermal insulations will not, of themselves, cause stress corrosion cracking. Preproduction qualification tests are used
to evaluate that under the conditions of the laboratory test that specific thermal insulation materials do not cause cracking of
sensitized austenitic stainless steel. Insulation systems have the potential to act as collecting media by means of transmigration and
concentration of corrosive ions on heated stainless steel surfaces. Exposure to elevated temperature results in evaporation of water
and increased chemical reaction rates. Environments containing corrosive ions, moisture, and oxygen will increase the chance for
stress corrosion cracking.
5.4 Insulation materials are available that are specially formulated to inhibit stress corrosion cracking in the presence of
chlorides through modifications in basic composition or incorporation of certain chemical additives.
5.5 The ability of the 28-day test to measure the corrosion potential of insulation materials is documented by Karnes, whose
data appear to have been used for construction of the acceptability curve used in Specification C795 and other specifications.
5.6 The metal for all of the coupons used in this test method (C692) shall be qualified (see Section 14) to ascertain that under
conditions of the test, chloride ions will cause the metal to crack, and deionized water alone will not cause cracks.
6. Applicability (see also 11.2)
6.1 While the original test procedure for the 1977 edition of this test method (Dana Test) was limited to “wicking-type
insulations,” the “drip test procedure” given in this edition is applicable to all insulations when cut or formed into the required test
specimen.
6.2 Heat treatment at some temperature (as recommended by the manufacturer) up to the maximum use temperature is
sometimes necessary to make the insulating material “wick,” and thus testable by either insulation test procedure (see Sections 12
and 13).
6.3 If the test insulation cannot be made to wick in any way (such as in the case of organic or inorganic closed-cell foams), or
when heat treatment of a component of the insulation (such as an attached exterior jacket material) exceeds the manufacturer’s
recommended maximum temperature for the exterior component, then the 1 ⁄2-in. (38-mm) wide test specimen is sliced into two
⁄4-in. (19-mm) thick segments. The two halves are held together with wire, pins, or a rubber band, and are tested by dripping into
the crack between the two halves, thus simulating the situation where water penetrates the junction between two sections of
insulation. Wetting the mating faces on the two half sections facilitates water wicking down to the coupon surface.
6.4 Adhesives are tested by gluing together a test block of the insulation material to be used with the adhesive. The adhesive
joint must come into contact with the stainless steel test coupon.
6.5 Cements with a clay binder are tested by casting a 1 ⁄2-in. (38-mm) thick slab, drying, and using the drip procedure. Such
a sample will disintegrate in the Dana test procedure.
6.6 The drip procedure has the potential to be used for the testing of coatings applied to the coupon prior to test. The corrosive
liquids dripped into such a system are limited only by the imagination of the researcher.
Whorlow, Kenneth M., Woolridge, Edward and Hutto, Francis B., Jr., “Effect of Halogens and Inhibitors on the External Stress Corrosion Cracking of Type 304 Austenitic
Stainless Steel”; STP 1320 Insulation Materials: Testing and Applications, Third Volume, Ronald S. Graves and Robert R. Zarr, editors , ASTM West Conshohocken, PA,
1997 page 485
Karnes, H. F., “The Corrosion Potential of Wetted Thermal Insulation,” AICHE, 57th National Meeting, Minneapolis, MN, September 26 through 29, 1965.
C692 − 13 (2018)
7. Apparatus for Dana Test Procedure
7.1 Enclosure—In dusty environments, it is permissible for the test apparatus to be located in a cabinet or other closed structure
provided with a blower to maintain a positive internal pressure, and equipped with a filter for intake air to minimize dust or other
contamination. The test apparatus is normally housed in any suitable clean environment not subject to chloride contamination. The
enclosure shall not be so tight as to exclude oxygen from the system, since oxygen is necessary for ESCC to occur.
7.2 Pyrex Glass Wool.
1 3
7.3 “Cookie Cutter,” made from 1 ⁄4 in. (32 mm) thin wall electrical conduit (inside diameter 1.38 in. (35 mm)) to cut a 1 ⁄8-in.
(35-mm) diameter plug from 2-in. (51-mm) Pyrex Glass Wool.
7.4 Specimen Holder, as shown in Fig. 1, or equivalent.
7.5 Precision Bender, see Practice G30.
7.6 Wet-Grinding Belt Grinder, 80-grit.
1 1
7.7 Copper Lugs, commercial 2/0–4/0 solderless, or 2 by ⁄2 by ⁄8 in. (51 by 13 by 3.2 mm) copper tabs.
7.8 Silver Solder, and chloride-free flux for use with stainless steel.
7.9 Torch, acetylene or propane.
3 1
7.10 Bolt, stainless steel, ⁄16 in. (5 mm) in diameter and 2 ⁄2-in. (65-mm) long with insulating washer and nut for electrically
insulating the bolt from the U-bend specimen.
7.11 Hand-Held Magnifier, 10× or 30× binocular microscope, or both.
7.12 Band Saw.
7.13 Hole Saw, 2-in. (51-mm) outside diameter (optional).
7.14 Crystallizing Dish, of borosilicate glass, 7 ⁄2 in. (190 mm) in diameter by 4 in. (100 mm) in depth, or stainless steel pan
1 1
9 ⁄2 by 5 ⁄2 by 4 in. (41 by 140 by 102 mm) deep.
7.15 Electrical Transformer, isolation-type. (approximately 150 mV/150 AMP).
7.16 Thermocouple, 28 gage or smaller.
7.17 Epoxy Adhesive, aluminum filled.
7.18 Drill Bit, ⁄32-in. (7-mm), cobalt steel preferred.
7.19 Dye Penetrant and Developer, available at most welding supply houses.
8. Apparatus for Drip Test Procedure
8.1 Steam Heated Pipe—A 5-ft (1.5-m) section of 1 ⁄2 in. IPS pipe (inconel or other corrosion-resistant material), is heated either
by a small self-contained steam boiler or by regulated house steam.
8.2 Peristaltic Pump—A multichannel peristaltic pump is used to supply 250 (625) mL/day to each specimen.
8.3 I.V. Bottles, 1 L or equivalent, to individually supply each test specimen with test liquid.
8.4 Specimen Holder, for grinding. See Fig. 1.
8.5 Precision Bender, see Fig. 2 in the 1979 edition of Practice G30.
8.6 Wet-Sanding Belt Sander, with 80-grit belt.
3 1
8.7 Bolt, stainless steel, ⁄16 in. (5 mm) in diameter by 2 ⁄2-in. (65-mm) long with nut.
8.8 Hole Saw, 2-in. (51-mm) outside diameter.
FIG. 1 Suction Cup Coupon Holder
C692 − 13 (2018)
FIG. 2 Typical External Stress Corrosion Cracks (5× Magnification)
8.9 Band Saw.
8.10 Thermocouple, 28 gage or smaller.
8.11 Heat Transfer Grease, chloride free.
8.12 Kimwipe Tissue, chloride free.
9. Reagents and Materials
9.1 Distilled or Deionized Water, containing less than 0.1 ppm chloride ions.
9.2 Distilled or Deionized Water, containing 1500 ppm chloride ion (2.473 g NaCl/L).
9.3 Type 304 Stainless Steel Sheet—16 gage, meeting the composition requirements of Specification A240/A240M. Certificates
of chemical composition and mechanical properties, including ultimate tensile strength and yield strength by the 0.2 % offset
method are required. Type 304 stainless steel meeting Specification A240/A240M shall have a carbon content in the range of
0.05–0.06 % and shall be solution-annealed.
10. Test Coupons
10.1 Shear 2 by 7-in. (51 by 178-mm) coupons from 16-gage Type 304 stainless sheet, as specified in 9.3, with the long
dimension parallel to the long dimension of the sheet. (Long dimension parallel to sheet-rolling direction.)
10.2 Clean coupons with chloride-free liquid soap and water to remove any grease or other contamination.
10.3 Sensitize all coupons before bending by heating at 1200°F (649°C) in an argon (inert) or air (oxidizing) atmosphere 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 the coupon temperatures “lag” the furnace temperature by at least 50 to 100°F (28 to 56°C).
10.4 A suggestion for sensitizing in an inert atmosphere is to use a stainless steel box with a tight-fitting cover to contain the
argon around the coupons during sensitization.
10.5 Grip coupon with suction cup holder (see Fig. 1) or other means to facilitate wet grinding on an 80-grit belt grinder. Grind
parallel to the long dimension of the coupon using an 80-grit wet belt with just enough pressure to remove the dull finish and leave
the metal bright. Do not overgrind. The beltground face is the test surface to be exposed to the thermal insulation. The test area
is the bent coupon surface that actually comes into contact with the insulation.
10.6 Smooth and round sheared edges to prevent accidental cutting of fingers.
10.7 Bend each ground coupon to a 1.00 6 0.01-in. (25.4 6 0.25-mm) outside radius using a roll bender as shown in Fig. 5
of the 1979 edition of Practice G3
...