1、Designation: G28 02 (Reapproved 2015)Standard Test Methods forDetecting Susceptibility to Intergranular Corrosion inWrought, Nickel-Rich, Chromium-Bearing Alloys1This standard is issued under the fixed designation G28; the number immediately following the designation indicates the year of originalad
2、option 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.This standard has been approved for use by agencies of the U.S. Department of Defe
3、nse.1. Scope1.1 These test methods cover two tests as follows:1.1.1 Method A, Ferric Sulfate-Sulfuric Acid Test (Sections310, inclusive)This test method describes the procedurefor conducting the boiling ferric sulfate50 % sulfuric acidtest which measures the susceptibility of certain nickel-rich,chr
4、omium-bearing alloys to intergranular corrosion (see Ter-minology G15), which may be encountered in certain serviceenvironments. The uniform corrosion rate obtained by this testmethod, which is a function of minor variations in alloycomposition, may easily mask the intergranular corrosioncomponents
5、of the overall corrosion rate on alloys N10276,N06022, N06059, and N06455.1.1.2 Method B, Mixed Acid-Oxidizing Salt Test (Sections1118, inclusive)This test method describes the procedurefor conducting a boiling 23 % sulfuric + 1.2 % hydrochlo-ric+1% ferric chloride+1% cupric chloride test whichmeasu
6、res the susceptibility of certain nickel-rich, chromium-bearing alloys to display a step function increase in corrosionrate when there are high levels of grain boundary precipitation.1.2 The purpose of these two test methods is to detectsusceptibility to intergranular corrosion as influenced by vari
7、a-tions in processing or composition, or both. Materials shown tobe susceptible may or may not be intergranularly corroded inother environments. This must be established independently byspecific tests or by service experience.1.3 This standard does not purport to address all of thesafety concerns, i
8、f 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. Warning statementsare given in 5.1.1, 5.1.3, 5.1.9, 13.1.1, and 13.1.11.2. Referenced Do
9、cuments2.1 ASTM Standards:2A262 Practices for Detecting Susceptibility to IntergranularAttack in Austenitic Stainless SteelsD1193 Specification for Reagent WaterG15 Terminology Relating to Corrosion and Corrosion Test-ing (Withdrawn 2010)3METHOD AFerric SulfateSulfuric Acid Test3. Significance and U
10、se3.1 The boiling ferric sulfate-sulfuric acid test may beapplied to the following alloys in the wrought condition:Alloy Testing Time, hN06007 120N06022 24N06030 120N06059 24N06200 24N06455 24N06600 24N06625 120N06686 24N06985 120N08020 120N08367 24N08800 120N08825A120N10276 24AWhile the ferric sulf
11、ate-sulfuric acid test does detect susceptibility to inter-granular corrosion in Alloy N08825, the boiling 65 % nitric acid test, PracticesA262, Practice C, for detecting susceptibility to intergranular corrosion in stainlesssteels is more sensitive and should be used if the intended service is nitr
12、ic acid.3.2 This test method may be used to evaluate as-receivedmaterial and to evaluate the effects of subsequent heat treat-ments. In the case of nickel-rich, chromium-bearing alloys, thetest method may be applied to wrought and weldments ofproducts. The test method is not applicable to cast produ
13、cts.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 Tests.Current edition approved Nov. 1, 2015. Published November 2015. Originallyapproved in 1971. Last previous edition appro
14、ved in 2008 as G2802 (2008). DOI:10.1520/G0028-02R15.2For 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 onthe ASTM website.3The las
15、t approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Apparatus4.1 The apparatus (Note 1) is illustrated in Fig. 1.4.1.1 Allihn or Soxhlet Condenser, 4-bulb,4wit
16、h a 45/50ground-glass joint, overall length about 330 mm, condensingsection about 240 mm.4.1.2 Erlenmeyer Flask, 1-L, with a 45/50 ground-glassjoint. The ground-glass opening shall be 40 mm wide.4.1.3 Glass Cradle (Fig. 2)To pass through the ground-glass joint on the Erlenmeyer flask, the width of t
17、he cradleshould not exceed 40 mm and the front-to-back distance mustbe such that the cradle will fit the 40-mm diameter opening. Itshould have three or four holes to increase circulation of thetest solution around the specimen (Note 2).NOTE 1Substitution for this equipment may not be used. Thecold-f
18、inger type of standard Erlenmeyer flask may not be used.NOTE 2Other equivalent means of specimen support, such as glasshooks or stirrups, may also be used.4.1.4 Boiling Chips,5or some other boiling aids must beused to prevent bumping.4.1.5 Silicone Grease, (for example, stopcock grease) isrecommende
19、d for the ground-glass joint.4.1.6 Electrically Heated Hot Plate, or equivalent to pro-vide heat for continuous boiling of the solution.4.1.7 Analytical Balance, capable of weighing to the nearest0.001 g.5. Test Solution5.1 Prepare 600 mL of 50 % (49.4 to 50.9 %) solution asfollows:5.1.1 WarningProt
20、ect the eyes and use rubber gloves forhandling acid. Place the test flask under a hood.5.1.2 First, measure 400 mL of Type IV reagent water(Specification D1193) in a 500-mL graduate and pour into theflask.5.1.3 Then measure 236 mL of reagent-grade sulfuric acid(H2SO4) of a concentration which must b
21、e in the range from95.0 to 98.0 weight percent in a 250-mL graduate.Add the acidslowly to the water in the flask to avoid boiling by the heatevolved (Note 3). Externally cooling the flask with waterduring the mixing will also reduce overheating.NOTE 3Loss of vapor results in concentration of the aci
22、d.5.1.4 Weigh 25 g of reagent grade ferric sulfate (containsabout 75 % Fe2(SO4)3(Note 4) and add to the H2SO4solution. A trip balance may be used.NOTE 4Ferritic sulfate is a specific additive that establishes andcontrols the corrosion potential. Substitutions are not permitted.5.1.5 Add boiling chip
23、s.5.1.6 Lubricate the ground glass of the condenser joint withsilicone grease.5.1.7 Cover the flask with the condenser and circulatecooling water.5.1.8 Boil the solution until all ferric sulfate is dissolved.5.1.9 WarningIt has been reported that violent boilingcan occur resulting in acid spills. It
24、 is important to ensure thatthe concentration of acid does not increase and that an adequatenumber of boiling chips (which are resistant to attack by thetest solution) are present.56. Test Specimens6.1 A specimen having a total surface area of 5 to 20 cm2isrecommended.6.2 The intent is to test a spe
25、cimen representing as nearly aspossible the material as used in service. The specimens shouldbe cut to represent the grain flow direction that will see service,for example, specimens should not contain cross-sectionalareas unless it is the intent of the test to evaluate these. Onlysuch surface finis
26、hing should be performed as is required toremove foreign material and obtain a standard, uniform finishas specified in 6.4. For very heavy sections, specimens shouldbe maintained to represent the appropriate surface whilemaintaining reasonable specimen size for convenience intesting. Ordinarily, rem
27、oval of more material than necessarywill have little influence on the test results. However, in thespecial case of surface decarburization or of carburization (thelatter is sometimes encountered in tubing when lubricants orbinders containing carbonaceous materials are employed), itmay be possible by
28、 heavy grinding or machining to remove theaffected layer completely. Such treatment of test specimens isnot permissible, except in tests undertaken to demonstrate suchsurface effects.6.3 When specimens are cut by shearing, the deformedmaterial must be removed by machining or grinding to a depthequal
29、 to the thickness of the specimen to remove cold workedmetal.6.4 All surfaces of the specimen, including edges, should befinished using wet No. 80-grit or dry No. 120-grit abrasivepaper. If dry abrasive paper is used, polish slowly to avoidoverheating. Sand blasting should not be used.6.5 Residual o
30、xide scale has been observed to cause spuri-ous specimen activation in the test solution. Therefore, theformation of oxide scale in stamped codes must be prevented,and all traces of oxide scale formed during heat treatment mustbe thoroughly removed prior to stamping identification codes.6.6 The spec
31、imen dimensions should be measured includingthe edges and inner surfaces of any holes and the total exposedarea calculated.6.7 The specimen should then be degreased using suitablenonchlorinated agents such as soap and acetone, dried, andthen weighed to the nearest 0.001 g.7. Procedure7.1 Place the s
32、pecimen in the glass cradle, remove thecondenser, immerse the cradle by means of a hook in the4To avoid frequent chipping of the drip-tip of the condenser during handling, themodified condenser described by Streicher, M. A., and Sweet, A. J., Corrosion,Vol25, 1969, pp. 1, has been found suitable for
33、 this use.5The sole source of supply of the apparatus known to the committee at this timeis amphoteric alundum Hengar Boiling Granules, available from Hengar Company,a division of Henry Troemner, LLC, 201 Wolf Drive, Thorofare, NJ 08086. If youare aware of alternative suppliers, please provide this
34、information to ASTMInternational Headquarters. Your comments will receive careful consideration at ameeting of the responsible technical committee,1which you may attend.G28 02 (2015)2FIG. 1 Apparatus for Ferric Sulfate-Sulfuric Acid TestG28 02 (2015)3FIG. 2 Glass CradleG28 02 (2015)4actively boiling
35、 solution (Fig. 1), and immediately replace thecondenser. A fresh solution should be used for each test.7.2 Mark the liquid level on the flask with wax crayon toprovide a check on vapor loss which would result in concen-tration of the acid. If there is an appreciable change in the level(a 0.5-cm or
36、more drop), repeat the test with fresh solution andwith a fresh specimen or a reground specimen.7.3 Continue immersion of the specimen for the length oftime specified in Section 3, then remove the specimen, rinse inwater and acetone, and dry.7.4 Weigh the specimen and subtract this mass from theorig
37、inal mass.7.5 Intermediate weighing is not necessary, except as notedin 7.7. The tests can be run without interruption. However, ifpreliminary results are desired, the specimen can be removed atany time for weighing.7.6 Replacement of acid is not necessary during the testperiods.7.7 If the corrosion
38、 rate is extraordinarily high in MethodA,as evidenced by a change in color (green) of the solution,additional ferric sulfate must be added during the test. Theamount of ferric sulfate that must be added, if the total massloss of all specimens exceeds2gasindicated by an interme-diate weight, is 10 g
39、for each1gofdissolved alloy. This doesnot apply to Method B.7.8 In Method A, several specimens of the same alloy maybe tested simultaneously. The number (3 or 4) is limited onlyby the number of glass cradles that can be fitted into the flaskand the consumption of ferric sulfate. Only one sample shou
40、ldbe tested in a flask for Method B.7.9 During testing, there is some deposition of iron oxideson the upper part for the flask. This can be readily removedafter test completion by boiling a solution of 10 % hydrochlo-ric acid (HCl) in the flask.8. Calculation and Interpretation of Results8.1 Calcula
41、tionMeasure the effect of the acid solution onthe mat.Corrosion Rate 5 K 3W!/A 3T 3D! (1)where:K = a constant (see 8.1.1),T = time of exposure, h, to the nearest 0.01 h,A = area, cm2, to the nearest 0.01 cm2,W = mass loss, g, to the nearest 0.001 g, andD = density, g/cm3(see 8.1.2).8.1.1 Many differ
42、ent units are used to express corrosionrates. Using the above units for T, A, W, and D, the corrosionrate can be calculated in a variety of units with the followingappropriate value of K:Corrosion Rate Units DesiredConstant K in Corrosion RateEquationAmils per year (mpy) 3.45 106inches per year (ipy
43、) 3.45 103inches per month (ipm) 2.87 102millimetres per year (mm/Y) 8.76 104micrometres per year (m/y) 8.76 107picometres per second (pm/s) 2.78 106grams per square metre-hour (g/m2-h) 1.00 104DBmilligrams per square decimetre-day (mdd) 2.40 106DBmicrograms per square metre-second (g/m2-s) 2.78 106
44、DBAIf desired, these constants may also be used to convert corrosion rates from oneset of units to another. To convert a corrosion rate in units X toarateinunitsY,multiply by KY/KX. For example:15 mpy5 153fs2.783106d/s3.453106dg pm/s512.1 pm/sBDensity is not needed to calculate the corrosion rate in
45、 these units. The densityin the constant K cancels out the density in the corrosion rate equation.8.1.2UNS Designation Density, g/cm3N06007 8.31N06022 8.69N06030 8.22N06059 8.80N06200 8.50N06455 8.64N06600 8.41N06625 8.44N06686 8.73N06985 8.31N08020 8.05N08367 8.06N08800 8.03N08825 8.14N10276 8.878.
46、2 Interpretation of ResultsThe presence of intergranularcorrosion is usually determined by comparing the calculatedcorrosion rate to that for properly annealed material. Even inthe absence of intergranular corrosion, the rate of general orgrain-face corrosion of properly annealed material will varyf
47、rom one alloy to another. These differences are demonstratedin Refs (1-7).68.3 As an alternative or in addition to calculating a corro-sion rate from mass loss data, metallographic examination maybe used to evaluate the degree of intergranular corrosion. Thedepth of attack considered acceptable shal
48、l be determinedbetween buyer and seller.9. Report9.1 Record the test procedure used, specimen size andsurface preparation, time of test, temperature, and mass loss.9.2 Report following information:9.2.1 Alloy number and heat number,9.2.2 Chemical composition and thermal treatment,9.2.3 Test method u
49、sed, and9.2.4 Calculated corrosion rate in units desired.10. Precision and Bias710.1 The precision of the procedure in Test Method A ofTest Methods G28 was determined in an interlaboratory testprogram with six laboratories running duplicate tests of threeheat treatments of a single material. Precision consists of6The boldface numbers in parentheses refer to a list of references at the end ofthis standard.7Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:G01-1002.G28 0
