ASTM D7671-10
(Test Method)Standard Test Method for Corrosiveness to Silver by Automotive Spark–Ignition Engine Fuel–Silver Strip Method
Standard Test Method for Corrosiveness to Silver by Automotive Spark<span class='unicode'>–</span>Ignition Engine Fuel<span class='unicode'>–</span>Silver Strip Method
SIGNIFICANCE AND USE
Crude petroleum contains sulfur compounds, most of which are removed during refining. However, of the sulfur compounds remaining in the petroleum product, some can have a corroding action on various metals and this corrosivity is not related to the total sulfur content. In addition, fuels can become contaminated by corrosive sulfur compounds during storage and distribution. The corrosive effect can vary according to the chemical types of sulfur compounds present.
The silver strip corrosion test is designed to assess the relative degree of corrosivity of a petroleum product towards silver and silver alloys.
Reactive sulfur compounds present in automotive spark-ignition engine fuels under some circumstances can corrode or tarnish silver alloy fuel gauge in-tank sender units (and silver-plated bearings in some 2-stroke cycle engines). To minimize or prevent the failure of silver alloy in-tank sender units by corrosion or tarnish, Specification D4814 requires that fuels shall pass the silver strip corrosion test.
SCOPE
1.1 This test method covers the determination of the corrosiveness to silver by automotive spark-ignition engine fuel, as defined by Specification D4814, or similar specifications in other jurisdictions, having a vapor pressure no greater than 124 kPa (18 psi) at 37.8°C (100°F), by one of two procedures. Procedure A involves the use of a pressure vessel, whereas Procedure B involves the use of a vented test tube.
1.2 The result of the test is based on a visual rating that is classified as an integer in the range from 0 to 4 as defined in Table 1.
1.3 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only.
1.4 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. For specific warning statements, see 6.1 and Section 7.
General Information
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Standards Content (Sample)
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Designation: D7671 – 10
Standard Test Method for
Corrosiveness to Silver by Automotive Spark–Ignition
Engine Fuel–Silver Strip Method
This standard is issued under the fixed designation D7671; 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.
TABLE 1 Silver Strip Classifications
1. Scope
1.1 This test method covers the determination of the corro- NOTE 1—Classifications provided by IP 227 Determination of Corro-
siveness to Silver of Aviation Turbine Fuels–Silver Strip Method.
siveness to silver by automotive spark-ignition engine fuel, as
NOTE 2—Distinctions between Classifications 1 and 2 are made using
defined by Specification D4814, or similar specifications in
The Color Standard for Tube Deposit Rating (referenced in Test Method
other jurisdictions, having a vapor pressure no greater than
D3241) in accordance with 11.1.1.
124 kPa (18 psi) at 37.8°C (100°F), by one of two procedures.
Classification Designation Description
Procedure A involves the use of a pressure vessel, whereas
0 No tarnish Identical to a freshly polished
Procedure B involves the use of a vented test tube.
strip, but may have some very
1.2 The result of the test is based on a visual rating that is
light loss of luster
classified as an integer in the range from 0 to 4 as defined in 1 Slight tarnish Faint brown or white discoloration
of strip (see 12.1)
Table 1.
2 Moderate tarnish Peacock colors such as blue or
1.3 The values stated in SI units are to be regarded as the
mauve or medium/dark straw or
brown coloration (see 12.1)
standard. The values in parentheses are for information only.
3 Slight blackening Spots and patches of black or
1.4 This standard does not purport to address all of the
gray on surface or uniform thin
safety concerns, if any, associated with its use. It is the
film of black deposit
4 Blackening Uniform heavy blackening with or
responsibility of the user of this standard to establish appro-
without scaling
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. For specific
warning statements, see 6.1 and Section 7.
E1 Specification for ASTM Liquid-in-Glass Thermometers
2. Referenced Documents
2.2 ASTM Adjunct: Color Standard for Tube Deposit
2.1 ASTM Standards:
Rating
D130 Test Method for Corrosiveness to Copper from Pe-
2.3 Energy Institute Standard:
troleum Products by Copper Strip Test
IP227 Determination of Corrosiveness to Silver ofAviation
D3241 Test Method for Thermal Oxidation Stability of
Turbine Fuels–Silver Strip Method
Aviation Turbine Fuels
D4057 Practice for Manual Sampling of Petroleum and
3. Summary of Test Method
Petroleum Products
3.1 This test method covers two procedures. Procedure A
D4177 Practice for Automatic Sampling of Petroleum and
involves the use of a pressure vessel (to prevent the loss of
Petroleum Products
volatile components in the sample), whereas Procedure B
D4814 Specification for Automotive Spark-Ignition Engine
involves the use of a vented test tube. In both procedures, a
Fuel
freshly polished silver strip is suspended in 30 mL of sample
which is heated to 50 6 1°C for a duration of 3 h 6 5 min.At
the end of the heating period, the silver strip is removed,
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and are the direct responsibility of Subcommit-
tee D02.05.0C on Color and Reactivity.
Current edition approved Oct. 1, 2010. Published November 2010. DOI:
10.1520/D7671–10. Available from ASTM International Headquarters. Order Adjunct No.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or ADJD3241. Original adjunct produced in 1986.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Withdrawn without replacement in 2001. Copies of IP 227/99 can be obtained
Standards volume information, refer to the standard’s Document Summary page on at The Publications Department, Energy Institute, 61 New Cavendish Street,
the ASTM website. London, W1G 7AR, United Kingdom.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7671 – 10
washed and the color and tarnish level assessed against the
requirements in Table 1.
4. Significance and Use
4.1 Crude petroleum contains sulfur compounds, most of
which are removed during refining. However, of the sulfur
compoundsremaininginthepetroleumproduct,somecanhave
a corroding action on various metals and this corrosivity is not
related to the total sulfur content. In addition, fuels can become
contaminated by corrosive sulfur compounds during storage
and distribution. The corrosive effect can vary according to the
chemical types of sulfur compounds present.
4.2 The silver strip corrosion test is designed to assess the
relative degree of corrosivity of a petroleum product towards
silver and silver alloys.
4.3 Reactivesulfurcompoundspresentinautomotivespark-
ignition engine fuels under some circumstances can corrode or
tarnish silver alloy fuel gauge in-tank sender units (and
silver-plated bearings in some 2-stroke cycle engines). To
minimize or prevent the failure of silver alloy in-tank sender
units by corrosion or tarnish, Specification D4814 requires that
fuels shall pass the silver strip corrosion test.
Key:
1. Lifting eye
5. Apparatus
2. Wide groove for pressure relief
3. Knurled cap
5.1 Silver Strip Corrosion Pressure Vessel (Procedure A),
4. Twelve threads per inch NF thread or equivalent
constructed from stainless steel or similar strong and non-
5. Camber inside cap to protect “O” ring when closing pressure vessel
corroding metallurgy according to the dimensions as given in
6. Synthetic rubber “O” ring without free sulfur
7. Seamless tube
Fig. 1, that is the apparatus described in Test Method D130.
The vessel shall be capable of withstanding a test pressure of
Material: stainless steel
700 kPa gauge (100 psi).
Welded construction
Maximum test gauge pressure: 700 kPa
5.1.1 Alternative designs for the vessel’s cap and synthetic
rubber gasket may be used provided that the internal dimen-
sions of the vessel are the same as those shown in Fig. 1. The NOTE 1—Dimensions in millimetres.
NOTE 2—All dimensions without tolerance limits are nominal values.
internal dimensions of the pressure vessel are such that a
FIG. 1 Pressure Vessel for Silver Strip Corrosion Test
nominal 25-mm by 150-mm test tube can be placed inside the
(Procedure A)
pressure vessel.
5.2 Test Tubes, of borosilicate glass of nominal 25-mm by
150-mm dimensions.The internal dimensions shall be checked 5.4.3 Other assemblies or designs capable of meeting the
as acceptable by use of a silver strip (see 6.3). When 30 mLof functional requirement may also be used in ProceduresAor B.
liquid is added to the test tube with the silver strip in it, a 5.5 Test Bath:
minimum of 5-mm of liquid shall be above the top surface of 5.5.1 General—The test baths shall be able to maintain the
the strip. test temperature to within 61°C (2°F) of the required test
5.3 Stoppers(ProcedureB), such as cork, to accompany test temperature (normally 50ºC).
tubes in 5.2. Each stopper shall have a vent hole to equilibrate 5.5.2 Liquid Bath Used for Submerging Pressure Vessel(s)
(Procedure A)—The bath shall be deep enough to submerge
pressure that may build up in the test. The stoppers should be
drilledthroughthecenterandfittedwithalengthof3.2mm( ⁄8 one or more pressure vessels (see 5.1) completely during the
in.) OD glass or Nalgene vent tube. test. As the bath medium, use water or any liquid that can be
5.4 Silver Strip Suspension Assembly, such as examples satisfactorily controlled to the sample test temperature. The
shown in Fig. 2 (ProcedureA) or Fig. 3 (Procedure B), capable bath shall be fitted with suitable supports to hold each pressure
of suspending the silver strip in approximately the center of the vesselinaverticalpositionwhensubmerged.Theuseofasolid
sample-filled test tube during the test, such that the strip is kept block bath has been found as a suitable alternative to the liquid
in an upright and vertical position. bath.
5.4.1 For Procedure A, a cradle of glass, polytetrafluoroet- 5.5.3 Liquid Bath Used for Vented Test Tube Method (Pro-
hyleneorotherinertmaterialconnectedtoaholderofsufficient cedure B)—The bath liquid level shall be at a level that is
length and width as shown in Fig. 2 has been found suitable to higher than the liquid level in the test tube at the test
use. temperature. It is recommended that the bath be placed inside
5.4.2 For Procedure B, a cable tie (see 6.2) wrapped around an exhaust hood.
the edges of the strip and inserted through the stopper has been 5.5.4 The use of a solid block bath has been found to be a
found suitable to use for this purpose as shown in Fig. 3. suitable alternative to the liquid bath.
D7671 – 10
Key:
1. Stopper
FIG. 2 Silver Strip Suspension Assembly (Procedure A)
2. Vent tube
3. Cable tie
4. Silver strip
5.6 Temperature Sensing Device (TSD), capable of monitor-
5. Test tube
ing the desired test temperature in the bath to within accuracy
FIG. 3 Silver Strip Suspension Assembly (Procedure B)
of 61°C (2°F), measured in the middle of the liquid bath. The
ASTM 12C (12F) (see Specification E1) orASTM E2251 (see
5.11.1 Keep the plastic-encased ASTM Silver Strip Corro-
Specification E1) or IP 64C (64F) total immersion thermom-
sion Standards protected from light to avoid the possibility of
eters have been found suitable for use in the test. If used, no
fading. Inspect for fading by comparing two different plaques,
more than 10-mm (0.4-in.) of the mercury should extend above
one of which has been carefully protected from light (for
the surface of the bath at the test temperature.
example, new plaque). Observe both sets in diffused daylight
5.7 PolishingVise,forholdingthesilverstripfirmlywithout
(or equivalent) first from a point directly above and then from
marring the edges while polishing. Any convenient type of
an angle of 45°. If any evidence of fading is observed,
holder (see Appendix X1) may be used provided that the strip
particularly at the left-hand end of the plaque, it is suggested
is held tightly and that the surface of the strip being polished is
that the one that is the more faded with respect to the other be
supported above the surface of the holder.
discarded.
5.8 Viewing Test Tubes, (optional) flat glass test tubes, are
5.11.1.1 Alternatively, place a suitably sized opaque strip
convenient for protecting corroded silver strips for close
(for example, 20-mm ( ⁄4-in.) black electrical tape) across the
inspection or storage (see Appendix X1 for the description of
top of the colored portion of the plaque when initially
a flat-glass viewing tube). The viewing test tube shall be of
purchased. At intervals remove the opaque strip and observe.
such dimensions as to allow the introduction of a silver strip
When there is any evidence of fading of the exposed portion,
(see 6.3) and made of glass free of striae or similar defects.
the standards shall be replaced.
5.9 Forceps, with either stainless steel or polytetrafluoroet-
5.11.2 The plaques are full-color reproductions of typical
hylene tips, for use in handling the silver strips, have been
strips.Theyhavebeenprintedonaluminumsheetsbya4-color
found suitable to use.
process and are encased in plastic for protection. Directions for
5.10 Timing Device, electronic or manual, capable of accu-
their use are given on the reverse side of each plaque.
rately measuring the test duration within the allowable toler-
5.11.3 If the surface of the plastic cover shows excessive
ance.
scratching, it is suggested that the plaque be replaced.
5.11 ASTM Silver Strip Corrosion Standards, consist of
6. Reagents and Materials
reproductions in color of typical test strips representing in-
creasing degrees of tarnish and corrosion, the reproductions 6.1 Ashless Filter Paper or Disposable Gloves, for use in
being encased for protection in plastic and made up in the form protecting the silver strip from coming in contact with the
of a plaque. See Table 1. individual during final polishing.
D7671 – 10
6.2 Cable Tie—Inert ties such as nylon ties of approximate 9. Preparation of Test Strips
dimensions 2 mm 3 208 mm.
9.1 Surface Preparation—Remove all surface blemishes
6.3 Silver Strips—Use strips 12.5 to 12.7-mm wide, 2.5 to
from all six sides of the strip obtained from a previous analysis
3.0-mm thick, and 17.0 to 19.0-mm long assaying at 99.9 %
(see Note 1). Use silicon carbide paper or cloth of such degrees
(m/m)Ag minimum, which are the same specification require-
of fineness as are needed to accomplish the desired results
ments described in IP 227. The strips may be used repeatedly
efficiently. Finish with 53 to 65-µm (240-grit) silicon carbide
but should be discarded when the strip’s surface shows pitting
paperorcloth,removingallmarksthatmayhavebeenmadeby
or deep scratches that cannot be removed by the specified
other grades of paper used previously. Immerse the strip in
polishing procedure, or when the surface becomes deformed.
2,2,4-trimethylpentane from which it can be withdrawn imme-
6.4 Surface Preparation/Polishing Materials, silicon car- diately for final preparation (polishing) or in which it can be
stored for future use.
bidegritpaperorclothofvaryingdegreesoffinenessincluding
53 to 65-µm (240-grit) grade; also a supply of 105-µm
9.1.1 As a practical manual procedure for surface prepara-
(150-mesh) size silicon carbide grain or powder and absorbent
tion, place a sheet of silicon carbide paper or cloth on a flat
cotton (cotton wool). A commercial grade of absorbent cotton
surface and moisten it with wash solvent. Rub the strip against
is suitable, but pharmaceutical grade is most commonly avail-
the silicon carbide paper or cloth with a circular motion,
able and is acceptable.
protecting the strip from contact with the fingers by using
ashless filter paper or wearing disposable gloves.Alternatively,
6.5 Wash Solvent—2,2,4-trimethylpentane (isooctane) of
the surface of the strip may be prepared by use of motor-driven
minimum 99.75 % purity. (Warning—Extremely flammable.
machines using appropriate grades of dry paper or cloth.
See 7.1.)
9.1.2 Only final preparation (see 9.2) is necessary for
7. Hazards commercially purchased pre-polished strips.
9.2 Final Preparation—For strips prepared in 9.1 or new
7.1 Wash Solvent—2,2,4-trimethylpentane (isooctane):
...
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