1、Designation: D7671 10 (Reapproved 2015)Standard Test Method forCorrosiveness to Silver by Automotive SparkIgnitionEngine FuelSilver Strip Method1This standard is issued under the fixed designation D7671; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of the corro-siveness to silver by automoti
3、ve spark-ignition engine fuel, asdefined by Specification D4814, or similar specifications inother jurisdictions, having a vapor pressure no greater than124 kPa (18 psi) at 37.8 C (100 F), by one of two procedures.Procedure A involves the use of a pressure vessel, whereasProcedure B involves the use
4、 of a vented test tube.1.2 The result of the test is based on a visual rating that isclassified as an integer in the range from 0 to 4 as defined inTable 1.1.3 The values stated in SI units are to be regarded as thestandard. The values in parentheses are for information only.1.4 This standard does n
5、ot purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificwarning statements, see 6.
6、1 and Section 7.2. Referenced Documents2.1 ASTM Standards:2D130 Test Method for Corrosiveness to Copper from Petro-leum Products by Copper Strip TestD3241 Test Method for Thermal Oxidation Stability ofAviation Turbine FuelsD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4177 Pr
7、actice for Automatic Sampling of Petroleum andPetroleum ProductsD4814 Specification for Automotive Spark-Ignition EngineFuelE1 Specification for ASTM Liquid-in-Glass Thermometers2.2 Energy Institute Standard:IP 227 Determination of Corrosiveness to Silver of AviationTurbine FuelsSilver Strip Method3
8、2.3 ASTM Adjuncts:Color Standard for Tube Deposit Rating43. Summary of Test Method3.1 This test method covers two procedures. Procedure Ainvolves the use of a pressure vessel (to prevent the loss ofvolatile components in the sample), whereas Procedure Binvolves the use of a vented test tube. In both
9、 procedures, afreshly polished silver strip is suspended in 30 mL of samplewhich is heated to 50 C 6 1 C for a duration of 3 h 6 5 min.At the end of the heating period, the silver strip is removed,washed and the color and tarnish level assessed against therequirements in Table 1.4. Significance and
10、Use4.1 Crude petroleum contains sulfur compounds, most ofwhich are removed during refining. However, of the sulfurcompounds remaining in the petroleum product, some can havea corroding action on various metals and this corrosivity is notrelated to the total sulfur content. In addition, fuels can bec
11、omecontaminated by corrosive sulfur compounds during storageand distribution. The corrosive effect can vary according to thechemical types of sulfur compounds present.4.2 The silver strip corrosion test is designed to assess therelative degree of corrosivity of a petroleum product towardssilver and
12、silver alloys.4.3 Reactive sulfur compounds present in automotive spark-ignition engine fuels under some circumstances can corrode ortarnish silver alloy fuel gauge in-tank sender units (andsilver-plated bearings in some 2-stroke cycle engines). Tominimize or prevent the failure of silver alloy in-t
13、ank sender1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and are the direct responsibilityof Subcommittee D02.05.0C on Color and Reactivity.Current edition approved Oct. 1, 2015. Published December 2015. Originallyapproved in 2010
14、. Last previous edition approved in 2010 as D7671 101. DOI:10.1520/D7671-10R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page o
15、nthe ASTM website.3Withdrawn without replacement in 2001. Copies of IP 227/99 can be obtainedat The Publications Department, Energy Institute, 61 New Cavendish Street,London, W1G 7AR, United Kingdom.4Available from ASTM International Headquarters. Order Adjunct No.ADJD3241. Original adjunct produced
16、 in 1986.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1units by corrosion or tarnish, Specification D4814 requires thatfuels shall pass the silver strip corrosion test.5. Apparatus5.1 Silver Strip Corrosion Pressure Vessel (Procedur
17、e A),constructed from stainless steel or similar strong and non-corroding metallurgy according to the dimensions as given inFig. 1, that is the apparatus described in Test Method D130.The vessel shall be capable of withstanding a test pressure of700 kPa gauge (100 psi).5.1.1 Alternative designs for
18、the vessels cap and syntheticrubber gasket may be used provided that the internal dimen-sions of the vessel are the same as those shown in Fig. 1. Theinternal dimensions of the pressure vessel are such that anominal 25 mm by 150 mm test tube can be placed inside thepressure vessel.5.2 Test Tubes, of
19、 borosilicate glass of nominal 25 mm by150 mm dimensions. The internal dimensions shall be checkedas acceptable by use of a silver strip (see 6.3). When 30 mL ofliquid is added to the test tube with the silver strip in it, aminimum of 5 mm of liquid shall be above the top surface ofthe strip.5.3 Sto
20、ppers (Procedure B), such as cork, to accompany testtubes in 5.2. Each stopper shall have a vent hole to equilibratepressure that may build up in the test. The stoppers should bedrilled through the center and fitted with a length of 3.2 mm(18 in.) OD glass or Nalgene vent tube.5.4 Silver Strip Suspe
21、nsion Assembly, such as examplesshown in Fig. 2 (ProcedureA) or Fig. 3 (Procedure B), capableof suspending the silver strip in approximately the center of thesample-filled test tube during the test, such that the strip is keptin an upright and vertical position.5.4.1 For Procedure A, a cradle of gla
22、ss, polytetrafluoroeth-ylene or other inert material connected to a holder of sufficientlength and width as shown in Fig. 2 has been found suitable touse.5.4.2 For Procedure B, a cable tie (see 6.2) wrapped aroundthe edges of the strip and inserted through the stopper has beenfound suitable to use f
23、or this purpose as shown in Fig. 3.5.4.3 Other assemblies or designs capable of meeting thefunctional requirement may also be used in Procedures A or B.5.5 Test Bath:5.5.1 GeneralThe test baths shall be able to maintain thetest temperature to within 61 C (2 F) of the required testtemperature (normal
24、ly 50 C).5.5.2 Liquid Bath Used for Submerging Pressure Vessel(s)(Procedure A)The bath shall be deep enough to submergeone or more pressure vessels (see 5.1) completely during thetest. As the bath medium, use water or any liquid that can besatisfactorily controlled to the sample test temperature. Th
25、ebath shall be fitted with suitable supports to hold each pressurevessel in a vertical position when submerged.The use of a solidblock bath has been found as a suitable alternative to the liquidbath.5.5.3 Liquid Bath Used for Vented Test Tube Method (Pro-cedure B)The bath liquid level shall be at a
26、level that ishigher than the liquid level in the test tube at the testtemperature. It is recommended that the bath be placed insidean exhaust hood.TABLE 1 Silver Strip ClassificationsNOTE 1Classifications provided by IP 227 Determination of Corro-siveness to Silver of Aviation Turbine FuelsSilver St
27、rip Method.NOTE 2Distinctions between Classifications 1 and 2 are made usingThe Color Standard for Tube Deposit Rating (referenced in Test MethodD3241) in accordance with 11.1.1.Classification Designation Description0 No tarnish Identical to a freshly pol-ished strip, but may havesome very light los
28、s of lus-ter1 Slight tarnish Faint brown or white discol-oration of strip (see 12.1)2 Moderate tarnish Peacock colors such asblue or mauve or medium/dark straw or brown color-ation (see 12.1)3 Slight blackening Spots and patches of blackor gray on surface or uni-form thin film of black de-posit4 Bla
29、ckening Uniform heavy blackeningwith or without scalingKey:1. Lifting eye2. Wide groove for pressure relief3. Knurled cap4. Twelve threads per inch NF thread or equivalent5. Camber inside cap to protect “O” ring when closing pressure vessel6. Synthetic rubber “O” ring without free sulfur7. Seamless
30、tubeMaterial: stainless steelWelded constructionMaximum test gauge pressure: 700 kPaNOTE 1Dimensions in millimetres.NOTE 2All dimensions without tolerance limits are nominal values.FIG. 1 Pressure Vessel for Silver Strip Corrosion Test(Procedure A)D7671 10 (2015)25.5.4 The use of a solid block bath
31、has been found to be asuitable alternative to the liquid bath.5.6 Temperature Sensing Device (TSD), capable of monitor-ing the desired test temperature in the bath to within accuracyof 61 C (2 F), measured in the middle of the liquid bath. TheASTM 12C (12F) (see Specification E1) or ASTM E2251 (seeS
32、pecification E1) or IP 64C (64F) total immersion thermom-eters have been found suitable for use in the test. If used, nomore than 10 mm (0.4 in.) of the mercury should extend abovethe surface of the bath at the test temperature.5.7 Polishing Vise, for holding the silver strip firmly withoutmarring t
33、he edges while polishing. Any convenient type ofholder (see Appendix X1) may be used provided that the stripis held tightly and that the surface of the strip being polished issupported above the surface of the holder.5.8 Viewing Test Tubes, (optional) flat glass test tubes, areconvenient for protect
34、ing corroded silver strips for closeinspection or storage (see Appendix X1 for the description ofa flat-glass viewing tube). The viewing test tube shall be ofsuch dimensions as to allow the introduction of a silver strip(see 6.3) and made of glass free of striae or similar defects.5.9 Forceps, with
35、either stainless steel or polytetrafluoro-ethylene tips, for use in handling the silver strips, have beenfound suitable to use.5.10 Timing Device, electronic or manual, capable of accu-rately measuring the test duration within the allowable toler-ance.5.11 ASTM Silver Strip Corrosion Standards, cons
36、ist ofreproductions in color of typical test strips representing in-creasing degrees of tarnish and corrosion, the reproductionsbeing encased for protection in plastic and made up in the formof a plaque. See Table 1.5.11.1 Keep the plastic-encased ASTM Silver Strip Corro-sion Standards protected fro
37、m light to avoid the possibility offading. Inspect for fading by comparing two different plaques,one of which has been carefully protected from light (forexample, new plaque). Observe both sets in diffused daylight(or equivalent) first from a point directly above and then froman angle of 45. If any
38、evidence of fading is observed,particularly at the left-hand end of the plaque, it is suggestedthat the one that is the more faded with respect to the other bediscarded.5.11.1.1 Alternatively, place a suitably sized opaque strip(for example, 20 mm (34 in.) black electrical tape) across thetop of the
39、 colored portion of the plaque when initiallypurchased. At intervals remove the opaque strip and observe.When there is any evidence of fading of the exposed portion,the standards shall be replaced.5.11.2 The plaques are full-color reproductions of typicalstrips. They have been printed on aluminum sh
40、eets by a 4-colorprocess and are encased in plastic for protection. Directions fortheir use are given on the reverse side of each plaque.5.11.3 If the surface of the plastic cover shows excessivescratching, it is suggested that the plaque be replaced.FIG. 2 Silver Strip Suspension Assembly (Procedur
41、e A)Key:1. Stopper2. Vent tube3. Cable tie4. Silver strip5. Test tubeFIG. 3 Silver Strip Suspension Assembly (Procedure B)D7671 10 (2015)36. Reagents and Materials6.1 Ashless Filter Paper or Disposable Gloves, for use inprotecting the silver strip from coming in contact with theindividual during fin
42、al polishing.6.2 Cable TieInert ties such as nylon ties of approximatedimensions 2 mm 208 mm.6.3 Silver StripsUse strips 12.5 mm to 12.7 mm wide,2.5 mm to 3.0 mm thick, and 17.0 mm to 19.0 mm longassaying at 99.9 % (mm) Ag minimum, which are the samespecification requirements described in IP 227. Th
43、e strips maybe used repeatedly but should be discarded when the stripssurface shows pitting or deep scratches that cannot be removedby the specified polishing procedure, or when the surfacebecomes deformed.6.4 Surface Preparation/Polishing Materials, silicon car-bide grit paper or cloth of varying d
44、egrees of fineness including53 m to 65 m (240 grit) grade; also a supply of 105 m(150 mesh) size silicon carbide grain or powder and absorbentcotton (cotton wool). A commercial grade of absorbent cottonis suitable, but pharmaceutical grade is most commonly avail-able and is acceptable.6.5 Wash Solve
45、nt2,2,4-trimethylpentane (isooctane) ofminimum 99.75 % purity. (WarningExtremely flammable.See 7.1.)7. Hazards7.1 Wash Solvent2,2,4-trimethylpentane (isooctane):Harmful if inhaled. Use with adequate ventilation. Keep awayfrom heat, sparks, and open flame.Avoid prolonged or repeatedskin contact. Cons
46、ult MSDS for additional information.7.2 Automotive Spark-Ignition Fuel (typically gasoline)Harmful if inhaled. Use with adequate ventilation. Keep awayfrom heat, sparks, and open flame.Avoid prolonged or repeatedskin contact. Consult MSDS for additional information.8. Samples8.1 In accordance with P
47、ractice D4057 or D4177, or both, itis particularly important that all types of fuel samples becollected in clean, amber glass bottles, plastic bottles, or othersuitable containers that will not affect the corrosive propertiesof the fuel. Avoid the use of tin plate containers for collectionof samples
48、, since experience has shown that they may contrib-ute to the corrosiveness of the sample.8.2 Collect samples and close the container immediatelyafter taking the sample.Adequate headspace in the container isnecessary to provide room for possible thermal expansionduring transport. It is recommended t
49、hat volatile samples befilled between 70 % and 80 % of the containers capacity. Takecare during sampling to protect the samples from exposure todirect sunlight or even diffused daylight.8.3 Test the sample as soon as practical after sampling. Ifsamples are not to tested immediately, store in a refrigerator ata temperature below 5 C.8.4 If suspended water (that is, haze) is observed in thesample, dry by filtering a sufficient volume of sample throughmedium rapid qualitative filter paper, into the prescribed clean,dry test tube. Carry out this
