1、Designation: G48 11Standard Test Methods forPitting and Crevice Corrosion Resistance of StainlessSteels and Related Alloys by Use of Ferric ChlorideSolution1This standard is issued under the fixed designation G48; the number immediately following the designation indicates the year of originaladoptio
2、n or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover procedures for the determina-tion of the resistanc
3、e of stainless steels and related alloys topitting and crevice corrosion (see Terminology G15) whenexposed to oxidizing chloride environments. Six proceduresare described and identified as Methods A, B, C, D, E, and F.1.1.1 Method AFerric chloride pitting test.1.1.2 Method BFerric chloride crevice t
4、est.1.1.3 Method CCritical pitting temperature test fornickel-base and chromium-bearing alloys.1.1.4 Method DCritical crevice temperature test fornickel-base and chromium-bearing alloys.1.1.5 Method ECritical pitting temperature test for stain-less steels.1.1.6 Method FCritical crevice temperature t
5、est for stain-less steels.1.2 Method A is designed to determine the relative pittingresistance of stainless steels and nickel-base, chromium-bearing alloys, whereas Method B can be used for determiningboth the pitting and crevice corrosion resistance of these alloys.Methods C, D, E and F allow for a
6、 ranking of alloys byminimum (critical) temperature to cause initiation of pittingcorrosion and crevice corrosion, respectively, of stainlesssteels, nickel-base and chromium-bearing alloys in a standardferric chloride solution.1.3 These tests may be used to determine the effects ofalloying additives
7、, heat treatment, and surface finishes onpitting and crevice corrosion resistance.1.4 The values stated in SI units are to be regarded as thestandard. Other units are given in parentheses for informationonly.1.5 This standard does not purport to address all of thesafety concerns, if any, associated
8、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.2. Referenced Documents2.1 ASTM Standards:2A262 Practices for Detecting Susceptibility to IntergranularAtta
9、ck in Austenitic Stainless SteelsD1193 Specification for Reagent WaterE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE1338 Guide for Identification of Metals and Alloys inComputerized Material Property DatabasesG1 Practice for Preparing, Cleaning, and
10、 Evaluating Corro-sion Test SpecimensG15 Terminology Relating to Corrosion and CorrosionTesting3G46 Guide for Examination and Evaluation of PittingCorrosionG107 Guide for Formats for Collection and Compilation ofCorrosion Data for Metals for Computerized DatabaseInput3. Terminology3.1 Definitions of
11、 Terms Specific to This Standard:3.1.1 critical crevice temperature, nthe minimum tem-perature (C) to produce crevice attack at least 0.025-mm(0.001-in.) deep on the bold surface of the specimen beneaththe crevice washer, edge attack ignored.3.1.2 critical pitting temperature, n the minimum tem-pera
12、ture (C) to produce pitting attack at least 0.025-mm(0.001-in.) deep on the bold surface of the specimen, edgeattack ignored.1These test methods are under the jurisdiction of ASTM Committee G01 onCorrosion of Metals and are the direct responsibility of Subcommittee G01.05 onLaboratory Corrosion Test
13、s.Current edition approved Sept. 1, 2011. Published September 2011. Originallyapproved in 1976. Last previous edition approved in 2009 as G4803(2009). DOI:10.1520/G0048-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For An
14、nual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428
15、-2959, United States.3.2 The terminology used herein, if not specifically definedotherwise, shall be in accordance with Terminology G15.Definitions provided herein and not given in Terminology G15are limited only to this standard.4. Significance and Use4.1 These test methods describe laboratory test
16、s for com-paring the resistance of stainless steels and related alloys to theinitiation of pitting and crevice corrosion. The results may beused for ranking alloys in order of increasing resistance topitting and crevice corrosion initiation under the specificconditions of these methods. Methods A an
17、d B are designed tocause the breakdown of Type 304 at room temperature.4.2 The use of ferric chloride solutions is justified because itis related to, but not the same as, that within a pit or crevice siteon a ferrous alloy in chloride bearing environments (1, 2).4Thepresence of an inert crevice form
18、er of consistent dimension ona surface is regarded as sufficient specification of crevicegeometry to assess relative crevice corrosion susceptibility.4.3 The relative performance of alloys in ferric chloridesolution tests has been correlated to performance in certain realenvironments, such as natura
19、l seawater at ambient temperature(3) and strongly oxidizing, low pH, chloride containing envi-ronments (4), but several exceptions have been reported (4-7).4.4 Methods A, B, C, D, E, and F can be used to rank therelative resistance of stainless steels and nickel base alloys topitting and crevice cor
20、rosion in chloride-containing environ-ments. No statement can be made about resistance of alloys inenvironments that do not contain chlorides.4.4.1 Methods A, B, C, D, E, and F were designed toaccelerate the time to initiate localized corrosion relative tomost natural environments. Consequently, the
21、 degree of corro-sion damage that occurs during testing will generally be greaterthan that in natural environments in any similar time period.4.4.2 No statement regarding localized corrosion propaga-tion can be made based on the results of Methods A, B, C, D,EorF.4.4.3 Surface preparation can signif
22、icantly influence results.Therefore, grinding and pickling of the specimen will meanthat the results may not be representative of the conditions ofthe actual piece from which the sample was taken.NOTE 1Grinding or pickling on stainless steel surfaces may destroythe passive layer. A 24-h air passivat
23、ion after grinding or pickling issufficient to minimize these differences (8).4.4.4 The procedures in Methods C, D, E and F formeasuring critical pitting corrosion temperature and criticalcrevice corrosion temperature have no bias because the valuesare defined only in terms of these test methods.NOT
24、E 2When testing as-welded, cylindrical, or other non-flatsamples, the standard crevice formers will not provide uniform contact.The use of contoured crevice formers may be considered in suchsituations, but the use of a pitting test (Practices A, C, or E) should beconsidered.5. Apparatus5.1 Glassware
25、Methods A, B, C, D, E, and F provide anoption to use either wide mouth flasks or suitable sized testtubes. Condensers are required for elevated temperature testingwhen solution evaporation may occur. Glass cradles or hooksalso may be required.5.1.1 Flask Requirements, 1000-mL wide mouth. Tall formor
26、 Erlenmeyer flasks can be used. The mouth of the flask shallhave a diameter of about 40 mm (1.6 in.) to allow passage ofthe test specimen and the support.5.1.2 Test Tube Requirements, the diameter of the test tubeshall also be about 40 mm (1.6 in.) in diameter. If testingrequires use of a condenser
27、(described below), the test tubelength shall be about 300 mm (about 12 in.); otherwise, thelength can be about 150 to 200 mm (about 6 in. to 8 in.).5.1.3 Condensers, Vents and Covers:5.1.3.1 A variety of condensers may be used in conjunctionwith the flasks described in 5.1.1. These include the coldf
28、inger-type (see, for example, Practices A262, Practice C) orAllihn type condensers having straight tube ends or taperedground joints. Straight end condensers can be inserted througha bored rubber stopper. Likewise, a simple U tube condensercan be fashioned.NOTE 3The use of ground joint condensers re
29、quires that the mouth ofthe flask have a corresponding joint.5.1.3.2 U Tube Condensers, fitted through holes in anappropriate size rubber stopper can be used in conjunction withthe 300-mm test tube described in 5.1.2.5.1.3.3 When evaporation is not a significant problem,flasks can be covered with a
30、watch glass. Also, flasks as wellas test tubes can be covered with loosely fitted stoppers orplastic or paraffin type wraps.NOTE 4Venting must always be considered due to the possible buildup of gas pressure that may result from the corrosion process.5.1.4 Specimen Supports:5.1.4.1 One advantage of
31、using test tubes is that specimensupports are not required. However, placement of the specimendoes create the possible opportunity for crevice corrosion tooccur along the edge.NOTE 5See 14.2 concerning edge attack.5.1.4.2 When using flasks, specimens can be supported oncradles or hooks. Cradles, suc
32、h as those shown in Fig. 1,eliminate the necessity for drilling a support hole in the testspecimen. While the use of hooks requires that a specimensupport hole be provided, the hooks, as contrasted to the cradle,are easier to fashion. Moreover, they create only one potentialcrevice site whereas mult
33、iple sites are possible with the cradle.NOTE 6A TFE-fluorocarbon cradle may be substituted for glass.5.1.4.3 The use of supports for Methods B, D, and F crevicecorrosion specimens is optional.5.2 Water or Oil Bath, constant temperature.5.2.1 For Methods A and B, the recommended test tempera-tures ar
34、e 22 6 2C or 50 6 2C, or both.5.2.2 For Methods C, D, E, and F, the bath shall have thecapability of providing constant temperature between 0C and85C 6 1C.4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.G481125.3 Crevice FormersMethod B:5.3.1 Cylindric
35、al TFE-fluorocarbon Blocks, two for eachtest specimen. Each block shall be 12.7-mm (0.5 in.) indiameter and 12.7-mm high, with perpendicular grooves1.6-mm (0.063 in.) wide and 1.6-mm deep cut in the top ofeach cylinder for retention of the O-ring or rubber bands.Blocks can be machined from bar or ro
36、d stock.NOTE 7When testing as-welded, cylindrical, or other non-flatsamples, the standard crevice formers will not provide uniform contact.The use of contoured crevice formers may be considered in suchsituations, but the use of the pitting test (PracticeA) should be considered.The problem of matchin
37、g the crevice former to the sample surfacebecomes more difficult as the radius of the surface becomes smaller.5.3.2 Fluorinated Elastomers O-rings, or Rubber Bands,(low sulfur (0.02 % max), two for each test specimen.NOTE 8It is good practice to use all O-rings or all rubber bands in agiven test pro
38、gram.5.3.2.1 O-rings shall be 1.75 mm (0.070 in.) in crosssection; one ring with an inside diameter of about 20 mm (0.8in.) and one with an inside diameter of about 30 mm (1.1 in.).Rubber bands shall be one No. 12 (38-mm (1.5-in.) long) andone No. 14 (51-mm (2-in.) long).NOTE 9Rubber bands or O-ring
39、s can be boiled in water prior to useto ensure the removal of water-soluble ingredients that might affectcorrosion.5.4 Crevice FormersMethods D and F:5.4.1 A Multiple Crevice Assembly (MCA), consisting oftwo TFE-fluorocarbon segmented washers, each having anumber of grooves and plateaus, shall be us
40、ed. The crevicedesign shown in Fig. 2 is one of a number of variations of themultiple crevice assembly that is in use and commerciallyavailable.5NOTE 10When testing as-welded, cylindrical, or other non-flatsamples, the standard crevice formers will not provide uniform contact.The use of contoured cr
41、evice formers may be considered in suchsituations, but the use of pitting tests (Practices C or E) should beconsidered. The problem of matching the crevice former to the samplesurface becomes more difficult as the radius of the surface becomessmaller.5.4.2 Reuse of Multiple Crevice Assemblies, when
42、as-sembled to the specified torque, the TFE-fluorocarbon seg-mented washers should not deform during testing. Beforereuse, each washer should be inspected for evidence ofdistortion and other damage. If so affected, they should bediscarded. In some cases, the crevice formers may becomestained with co
43、rrosion products from the tested alloy. Gener-ally, this staining can be removed by immersion in dilute HCl(for example, 5-10% by volume) at room temperature, fol-lowed by brushing with mild detergent and through rinsingwith water.5.4.3 Fasteners, one alloy UNS N10276 (or similarly resis-tant alloy)
44、 fastener is required for each assembly. Eachassembly comprises a threaded bolt and nut plus two washers.The bolt length shall be sized to allow passage through themouth of the glassware described in 5.1.5The sole source of supply of the apparatus known to the committee at this timeis Metal Samples
45、Co., Inc., P.O. Box 8, Route 1 Box 152, Munford, AL 36268. Ifyou are aware of alternative suppliers, please provide this information to ASTMHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,1which you may attend.FIG. 1 Examples of Glass
46、 Cradles that Can Be Used to Support the SpecimenG481135.5 Tools and Instruments:5.5.1 A 6.35-mm (14-in.) torque limiting nut driver isrequired for assembly of the Methods D and F crevice testspecimen.5.5.2 Low Power Microscope, (for example, 203 magnifi-cation) for pit detection.5.5.3 Needle Point
47、Dial Depth Indicator or Focusing Mi-croscope, to determine the depth of pitting or crevice corro-sion, or both.5.5.4 Electronic Balance (optional), to determine specimenmass to the nearest 0.0001 g.5.5.5 Camera (optional), to photographically record themode and extent of any localized corrosion.6. F
48、erric Chloride Test Solution6.1 For Methods A and B, dissolve 100 g of reagent gradeferric chloride, FeCl36H2O, in 900 mL of Type IV reagentwater (Specification D1193) (about 6 % FeCl3by mass). Filterthrough glass wool or filter paper to remove insoluble particlesif present.6.2 For Methods C, D, E,
49、and F, dissolve 68.72 g of reagentgrade ferric chloride, FeCl36H2O in 600 mL of reagent waterand add 16 mL of reagent grade concentrated (36.538.0 %)hydrochloric acid (HCl). This will produce a solution contain-ing about 6 % FeCl by mass and 1 % HCl resulting in a pHcontrolled environment over the test temperatures (9).7. Test Specimens7.1 A test specimen 25 by 50 mm (1 by 2 in.) is recom-mended as a standard size, although various shapes and sizescan be tested by this method. All specimens in a test seriesshould have the same dimensions when comparis
