1、Designation: G 48 03Standard Test Methods forPitting and Crevice Corrosion Resistance of StainlessSteels and Related Alloys by Use of Ferric ChlorideSolution1This standard is issued under the fixed designation G 48; the number immediately following the designation indicates the year of originaladopt
2、ion or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscriptepsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover procedures for the determina-tion of the resist
3、ance of stainless steels and related alloys topitting and crevice corrosion (see Terminology G 15) 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 crevi
4、ce test.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 temperatu
5、re test 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 f
6、or a 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 addit
7、ives, 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, associa
8、ted 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:A 262 Practices for Detecting Susceptibility to Intergranu-la
9、r Attack in Austenitic Stainless Steels2D 1193 Specification for Reagent Water3E 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method4E 1338 Guide for the Identification of Metals and Alloys inComputerized Material Property Databases5G 1 Practice for Prepar
10、ing, Cleaning, and Evaluating Cor-rosion Test Specimens6G 15 Terminology Relating to Corrosion and CorrosionTesting6G 46 Guide for Examination and Evaluation of PittingCorrosion6G 107 Guide for Formats for Collection and Compilation ofCorrosion Data for Metals for Computerized DatabaseInput63. Termi
11、nology3.1 Definition of 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,
12、 n the minimum tem-perature (C) to produce pitting attack at least 0.025-mm(0.001-in.) deep on the bold surface of the specimen, edgeattack ignored.3.2 The terminology used herein, if not specifically definedotherwise, shall be in accordance with Terminology G 15.1These test methods are under the ju
13、risdiction of ASTM Committee G01 onCorrosion of Metals, and are the direct responsibility of Subcommittee G01.05 onLaboratory Corrosion Tests.Current edition approved May 10, 2003. Published July 2003. Originallyapproved in 1976. Last previous edition approved in 2000 as G 48 00.2Annual Book of ASTM
14、 Standards, Vol 01.03.3Annual Book of ASTM Standards, Vol 11.01.4Annual Book of ASTM Standards, Vol 14.02.5Annual Book of ASTM Standards, Vol 02.05.6Annual Book of ASTM Standards, Vol 03.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United St
15、ates.Definitions provided herein and not given in Terminology G 15are limited only to this standard.4. Significance and Use4.1 These test methods describe laboratory tests for com-paring the resistance of stainless steels and related alloys to theinitiation of pitting and crevice corrosion. The resu
16、lts may beused for ranking alloys in order of increasing resistance topitting and crevice corrosion initiation under the specificconditions of these methods. Methods A and B are designed tocause the breakdown of Type 304 at room temperature.4.2 The use of ferric chloride solutions is justified becau
17、se itis related to, but not the same as, that within a pit or crevice siteon a ferrous alloy in chloride bearing environments (1, 2).7Thepresence of an inert crevice former of consistent dimension ona surface is regarded as sufficient specification of crevicegeometry to assess relative crevice corro
18、sion susceptibility.4.3 The relative performance of alloys in ferric chloridesolution tests has been correlated to performance in certain realenvironments, such as natural seawater at ambient temperature(3) and strongly oxidizing, low pH, chloride containing envi-ronments (4), but several exceptions
19、 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 corrosion in chloride-containing environ-ments. No statement can be made about resistance of alloys inenvironments that do not contai
20、n 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 degree of corro-sion damage that occurs during testing will generally be greaterthan that in natural environments in any similar
21、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 significantly influence results.Therefore, grinding and pickling of the specimen will meanthat the results may not be representative of
22、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 passivation after grinding or pickling issufficient to minimize these differences (8).4.4.4 The procedures in Methods C, D, E and F formea
23、suring critical pitting corrosion temperature and criticalcrevice corrosion temperature have no bias because the valuesare defined only in terms of these test methods.5. Apparatus5.1 GlasswareMethods A, B, C, D, E, and F provide anoption to use either wide mouth flasks or suitable sized testtubes. C
24、ondensers 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 Erlenmeyer flasks can be used. The mouth of the flask shallhave a diameter of about 40 mm (1.6 in.) to allo
25、w 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 (described below), the test tubelength shall be about 300 mm (about 12 in.); otherwise, thelength can be abo
26、ut 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 coldfinger-type (see, for example, Practices A 262, Practice C) orAllihn type condensers having straight tube end
27、s or taperedground joints. Straight end condensers can be inserted througha bored rubber stopper. Likewise, a simple U tube condensercan be fashioned.NOTE 2The use of ground joint condensers requires that the mouth ofthe flask have a corresponding joint.5.1.3.2 U Tube Condensers, fitted through hole
28、s 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 watch glass. Also, flasks as wellas test tubes can be covered with loosely fitted stoppers orplastic or par
29、affin type wraps.NOTE 3Venting 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 using test tubes is that specimensupports are not required. However, placement of the specimendoes create t
30、he possible opportunity for crevice corrosion tooccur along the edge.NOTE 4See 14.2 concerning edge attack.5.1.4.2 When using flasks, specimens can be supported oncradles or hooks. Cradles, such as those shown in Fig. 1,eliminate the necessity for drilling a support hole in the testspecimen. While t
31、he 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 multiple sites are possible with the cradle.NOTE 5A TFE-fluorocarbon cradle may be substituted for glass.5.1.4.
32、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 are 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 provid
33、ing constant temperature between 0C and85C 6 1C.5.3 Crevice FormersMethod B:5.3.1 Cylindrical 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
34、 cylinder for retention of the O-ring or rubber bands.Blocks can be machined from bar or rod stock.7The boldface numbers in parentheses refer to the list of references at the end ofthis standard.G480325.3.2 Fluorinated Elastomers O-rings, or Rubber Bands,(low sulfur (0.02 % max), two for each test s
35、pecimen.NOTE 6It is good practice to use all O-rings or all rubber bands in agiven test program.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
36、. 12 (38-mm (1.5-in.) long) andone No. 14 (51-mm (2-in.) long).NOTE 7Rubber bands or O-rings 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 T
37、FE-fluorocarbon segmented washers, each having anumber of grooves and plateaus, shall be used. The crevicedesign shown in Fig. 2 is one of a number of variations of themultiple crevice assembly that is in use and commerciallyavailable.85.4.2 Reuse of Multiple Crevice Assemblies, when as-sembled to t
38、he 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 corrosion product
39、s 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) fastener is re
40、quired 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 5.1.5.5 Tools and Instruments:5.5.1 A 6.35-mm (14-in.) torque limiting nut driver isrequired for assembly of the Me
41、thods D and F crevice testspecimen.5.5.2 Low Power Microscope, (for example, 203 magnifi-cation) for pit detection.5.5.3 Needle Point 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 speci
42、menmass to the nearest 0.0001 g.5.5.5 Camera (optional), to photographically record themode and extent of any localized corrosion.8The sole source of supply of the apparatus known to the committee at this timeis Metal Samples Co., Inc., P.O. Box 8, Route 1 Box 152, Munford, AL 36268. Ifyou are aware
43、 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 Cradles that Can Be Used to Support the SpecimenFIG. 2 TFE-fluorocarbon C
44、revice WashersG480336. Ferric 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 D 1193) (about 6 % FeCl3by mass). Filterthrough glass wool or filter paper to remove insoluble particlesif present.
45、6.2 For Methods C, D, E, 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 pHcontroll
46、ed 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 comparisons are to bemade.
47、 Unless end-grain pitting is an integral part of theevaluation, the proportion of end-grain surface to specimensurface should be kept as small as possible given the limita-tions of specimen sizes because of the susceptibility ofend-grain surfaces to pitting.NOTE 8The thickness of the specimen in Met
48、hod B can influence thetightness of the crevice and the test results.NOTE 9End-grain attack in Methods C, D, E, and F may not be asprevalent in a test in which low test temperatures are anticipated.7.2 When specimens are cut by shearing, the deformedmaterial should be removed by machining or grindin
49、g prior totesting unless the corrosion resistance of the sheared edges isbeing evaluated. It is good practice to remove deformed edgesto the thickness of the material.7.3 For Methods D and F, a sufficient hole should be drilledand chamfered in the center of the specimen to accommodatethe bolt and insulating sleeve used to attach the crevice device.7.4 All surfaces of the specimen should be polished to auniform finish. A120-grit abrasive paper has been found toprovide a satisfactory standard finish. Wet polishing is pre-ferred, but if dry polishing is use
