ASTM D2688-94(1999)e1

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An American National Standard
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Designation: D 2688 – 94 (Reapproved 1999)
Standard Test Methods for
Corrosivity of Water in the Absence of Heat Transfer
(Weight Loss Methods)
This standard is issued under the fixed designation D 2688; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Footnotes were editiorially removed in July 1999.
1. Scope 2. Referenced Documents
1.1 These test methods cover the determination of the 2.1 ASTM Standards:
corrosivity of water by evaluating pitting and by measuring the A 120 Specification for Pipe, Steel, Black and Hot-Dipped
weight loss of metal specimens. Pitting is a form of localized Zinc-Coated (Galvanized) Welded and Seamless, for Or-
corrosion: weight loss is a measure of the average corrosion dinary Use
rate. The rate of corrosion of a metal immersed in water is a D 1129 Terminology Relating to Water
function of the tendency for the metal to corrode and is also a D 1193 Specification for Reagent Water
function of the tendency for water and the materials it contains D 2331 Practices for Preparation and PreliminaryTesting of
to promote (or inhibit) corrosion. Water-Formed Deposits
1.2 The following two test methods are included:
3. Terminology
Test Method Corrosivity Test of Sections
A Internal Metallic Pipes (Coupon) 10 to 18
3.1 Definitions: —For definitions of terms used in these test
B City and Building Distribution Water 19 to 30
methods, refer to Terminology D 1129.
(1,2,3,4,5)
1.3 Test Method A employs flat, rectangular-shaped metal 4. Significance and Use
coupons which are mounted on pipe plugs and exposed to the
4.1 Since the two tendencies are inseparable for a metal to
water flowing in metal piping in municipal, building, and
corrode and for water and the materials it contains to promote
industrial water systems.
or inhibit corrosion, the corrosiveness of a material or the
1.4 Test Method B employs removable, tared pipe inserts
corrosivity of water must be determined in relative, rather than
which are installed in a plastic piping assembly tailored to
absolute, terms. The tendency for a material to corrode is
provide the same surface and flow conditions as in a normal
normally determined by measuring its rate of corrosion and
metal piping system. Proper dimensions are provided through-
comparing it with the corrosion rates of other materials in the
out so that streamline flow (no-flow distortion) results and
same water environment. Conversely, the relative corrosivity
corrosion and scale formed on the inserts will be the same as
of water may be determined by comparing the corrosion rate of
that occurring in the metal piping system being tested. Steel,
a material in the water with the corrosion rates of the same
galvanized steel, and soldered copper and copper inserts have
material in other waters. Such tests are useful, for example, for
been found to provide meaningful corrosion test results by this
evaluating the effects of corrosion inhibitors on the corrosivity
test method.
of water. Although these test methods are intended to deter-
1.5 This standard does not purport to address all of the
mine the corrosivity of water, they are equally useful for
safety concerns, if any, associated with its use. It is the
determining corrosiveness and corrosion rate of materials.
responsibility of the user of this standard to establish appro-
5. Composition of Specimens
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For a specific
5.1 The specimens shall be similar in composition to the
hazard statement, see 26.1.1.
piping in the system in which the corrosion test is being made.
Welded or seamless pipe shall be used in Test Method B;
however, butt-welded piping specimens may be used in Test
These test methods are under the jurisdiction of ASTM Committee D-19 on
Water and are the direct responsibility of Subcommittee D19.03 on Sampling of
Water and Water-Formed Deposits, and Surveillance of Water.
Current edition approved April 15, 1994. Published June 1994. Originally Discontinued 1988 (Replaced by A 53)—See 1988 Annual Book of ASTM
published as D 2688 – 69. Last previous edition D 2688 – 92. Standards, Vol 01.01.
2 4
The boldface numbers in parentheses refer to the list of references at the end of Annual Book of ASTM Standards, Vol 11.01.
this standard. Annual Book of ASTM Standards, Vol 11.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D 2688 – 94 (1999)
Method B provided care is taken to pick smooth specimens 8. Water-Formed Deposits
(excluding butt joints).
8.1 Water-formed deposits observed on the specimens may
be analyzed by the methods listed in Practices D 2331. The
6. Effect of Cold Working on Corrosion
most common constituents will be calcium, magnesium, alu-
6.1 Cold working can be important in causing localized
minum, zinc, copper, iron, carbonate, phosphate, sulfate, chlo-
corrosion; however, plastic deformation can be minimized in
ride, and silica.
specimen preparation by following proper machining practices
9. Purity of Reagents
(6) (for example, drilling, reaming, and cutting specimens for
Test Method A). While the importance of proper preparation
9.1 Reagent grade chemicals shall be used in all tests.
and machining is recognized in the other test methods, it is
Unless otherwise indicated, it is intended that all reagents shall
considered important to retain stressed areas in the piping
conform to the specifications of the Committee on Analytical
inserts (Test Method B) since these specimens then have the
Reagents of the American Chemical Society, where such
same properties as the piping system being tested.
specifications are available. Other grades may be used, pro-
vided it is first ascertained that the reagent is of sufficiently
7. Types of Corrosion
high purity to permit its use without lessening the accuracy of
7.1 General Corrosion is characterized by uniform attack
the determination.
of the metal over the entire surface.
9.2 Purity of Water— Unless otherwise indicated, refer-
7.2 Pitting is a form of localized corrosion, the depth,
ences to water shall be understood to mean reagent water
number, size, shape, and distribution of pits being pertinent
conforming to Type III of Specification D 1193.
characteristics. It may be evaluated by counting the number, by
TEST METHOD A—Coupon
noting the size, shape, and distribution, and by measuring the
depth of pits in representative areas. Both sides of the coupons
10. Summary of Test Method
must be examined in Test Method A. In Test Method B the
10.1 Carefully prepared, weighed metal coupons are in-
specimens must be cut longitudinally before internal examina-
stalled in contact with flowing cooling water for a measured
tion for pitting can be performed.
length of time. After removal from the system, these coupons
7.2.1 A system may be devised for grading pitting (7).
are examined, cleaned, and reweighed. The corrosivity and
7.3 Crevice Corrosion is a pertinent factor to consider in
fouling characteristics of the water are determined from the
corrosion testing, since active corrosion sites may develop in
difference in weight, the depth and distribution of pits, and the
such locations. Crevices may exist at threads and joints and
weightandcharacteristicsoftheforeignmatteronthecoupons.
under deposits, as well as in corrosion specimens. In Test
Method A, crevice corrosion may be in evidence where the
11. Interferences
specimen is fastened to the holder and at coupon markings.
11.1 Deviation in metal composition or surface preparation
Providing a large specimen surface area relative to the crevice
of the coupons may influence the precision of the results.
area reduces this influence on the overall corrosion results.
11.2 The presence of different metals in close proximity to
Light sanding is necessary to remove edges of coupon mark-
the coupon, (within 76 mm (3 in.)), even if they are insulated
ing. In Test Method B, areas subject to crevice corrosion are
from the coupon, constitutes a source of error in the results.
coated with paint.
11.3 Deviationsinthevelocityanddirectionofflowpastthe
7.4 Edge Corrosion— The increased corrosion that occurs
coupons may influence the precision of the results.
at edges of corrosion specimens, where the metal may be of
11.4 Results are directly comparable only for the water
different composition or structure, must be given attention. In
temperature to which the coupon is exposed.
Test Method A, specimens of a high ratio of surface area to
11.5 Crevices, deposits, or biological growths may affect
edge area reduce this effect. In Test Method B, the edges are
local corrosivity; results should therefore be interpreted with
painted to prevent fluid contact. If an abnormally high degree
caution.
of edge corrosion is observed in the case ofTest MethodA, the
effect may be evaluated by measurement of the specimen
12. Apparatus
dimensions previous to and following exposure. Use of a
12.1 Coupon Specimens— Prepare coupons in accordance
specimen of less thickness may also reduce the edge effect in
with Section 14.
weight loss.
7.5 Impingement Attack (Erosion-Corrosion), associated
with turbulent and high-velocity flow, particularly when soft
Reagent Chemicals, American Chemical Society Specifications, American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
metals and copper are involved, is characterized by continuous
listed by the American Chemical Society, see Analar Standards for Laboratory
broader-type pits and bright metal from which protective films
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
have been scoured away. Some under-cutting also may be
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
present. MD.
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D 2688 – 94 (1999)
FIG. 1 Installation of Corrosion Coupons
12.2 Insulating Washer, Screw, and Nut—Use for attaching specimens first at two locations and over the specimen first at
the coupon to the phenolic rod. The insulating washer has a the other two locations. This enables one to determine whether
7,8
sleeve that fits into the coupon hole and around the screw. the turbulence provided by the corrosion testers or the elbows
12.3 Phenolic Rod— Use a 152-mm (6-in.) length of influences the results.
canvas-based 13-mm (0.5-in.) outside diameter phenolic rod,
12.5 Dial Depth Gage— A gage with a knife-edge base,
or equivalent, attached at one end to a drilled pipe plug, and
pointed probe, and dial indicator for measurement of pit depth.
having a flat surface and a hole at the other end suitable for
12.6 Emery Paper, Number 0.
attachment of the coupon.
12.4 Piping Arrangement, as illustrated in Fig. 1, for instal-
13. Reagents and Materials
lation of coupon specimens. This arrangement has been
13.1 Benzene.
changed in order that flow passes over the holder end of the
13.2 Chromic Acid-Phosphoric Acid Solution—Dissolve 30
g of chromic acid (chromium trioxide, CrO ) in approximately
500 mL of water and add 36 mL of phosphoric acid (H PO
3 4
Allied Industrial Electronics, 100 N. Western Ave., Chicago, IL 60680,
35 %). Dilute the resulting solution to 1L.
extruded fiber washer for No. 8 screw, Part No. 26D-3226, manufactured by G. C.
Electronics, Rockford, IL (as Part No. 6526C), has been found satisfactory for this
13.3 Chromium Trioxide (CrO ), anhydrous crystals.
purpose. The dimensions are as follows: outside diameter 9.5 mm ( ⁄8 in.), inside
13.4 Corrosion Inhibitor I, a liquid material having a flash
diameter of hole 4.0 mm ( ⁄32 in.), total thickness including the raised are
1 1
point of 71°F, which contains amino ketones of rosin, surface
approximately 1.5 mm ( ⁄16 in.), outside diameter of raised are 6.4 mm ( ⁄4 in.), and
thickness of raised are approximately 0.4 mm ( ⁄64 in.).
active agents, alcohols, and less than 10 % by volume of
It may be preferred to obtain the complete corrosion tester and coupons from
synergists, for hydrochloric acid.
Metal Samples, P.O. Box 8, Mumford, AL 36268, who construct the rod from
13.5 Corrosion Inhibitor II, a nonflammable liquid contain-
TFE-fluorocarbonornylon,includeascrewmadefromthissamematerialandavoid
the necessity of including a washer and nut by providing screw threads in the ing heterocyclic nitrogen bases (usually in the form of salts),
mounting.
surface active agents, and synergists, for sulfuric acid.
Phenolic rod meeting the National Electrical Manufacturers Association
13.6 Hydrochloric Acid (1 + 4)—Mix 1 volume of concen-
(NEMA) Grade CE or LE is satisfactory. The pipe plug is marked externally to
permit orientation of the coupon as desired. trated HCl (sp gr 1.19) with 4 volumes of water.
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D 2688 – 94 (1999)
13.7 Hydrochloric Acid, Inhibited—Mixed 357 mL of con- 14.4.4 Stamp identifying numbers or letters on the small
centrated HCl (sp gr 1.19) and 5.0 g of inhibitor (see 13.4). coupon area between the edge and the mounting hole.
Then dilute to 1 L with water. 14.4.5 The approximate weight of metal coupons, g, is as
13.8 Isopropyl Alcohol. follows:
13.9 Methyl Orange Indicator Solution (0.5 g/L)—Dissolve
Steel 10.35
Cast Iron 11.65
0.05 g of methyl orange in water and dilute to 100 mL with
Copper 13.33
water.
Zinc 8.7
13.10 Nitric Acid-Dichromate Solution—Mix 224 mL of
Lead 16.60
HNO (sp gr 1.42) with twice the volume of water.Add 22.75
14.5 Cleaning Ferrous Metal Coupons—Remove oil by
g of sodium dichromate (Na Cr O ·H O) and dissolve. Dilute
2 2 7 2
immersion in benzene. Dry. Immerse in a solution containing
the resulting solution to 1 L.
HCl (1 + 4) for 30 min at room temperature.
13.11 Sulfuric Acid, Inhibited—Slowly add 29 mL of
14.5.1 Remove acid from the coupon by three rapid succes-
H SO (sp gr 1.84) to approximately 500 mL of water. Add
2 4
sive rinses in separate water baths; the last rinse water bath
anddissolve0.5gofInhibitor II(see13.5).Dilutetheresulting
shall contain methyl orange solution and must be kept neutral
solution to 1 L with water.
(yellow). The first and second bath must be renewed fre-
13.12 Trichloroethylene.
quently. Rinse successively in isopropyl alcohol and benzene,
13.13 Tripoli—Finely granulated, porous, siliceous rock;
and dry with a clean cloth. Store in a desiccator.
amorphous silica (SiO ), soft, porous, and free of sharp edges
14.6 Cleaning Copper, Brass,
...