ASTM G1-2003 Standard Practice for Preparing Cleaning and Evaluating Corrosion Test Specimens《腐蚀试样的制备、清洁处理和评定用标准实施规范》.pdf

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1、Designation:G103Standard Practice forPreparing, Cleaning, and Evaluating Corrosion TestSpecimens1This standard is issued under the fixed designation G 1; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revision. A

2、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 This practice covers suggested procedures for preparingbare, solid metal specimens for tests, for removing corrosionproducts after the

3、 test has been completed, and for evaluatingthe corrosion damage that has occurred. Emphasis is placed onprocedures related to the evaluation of corrosion by mass lossand pitting measurements. (WarningIn many cases thecorrosion product on the reactive metals titanium and zirco-nium is a hard and tig

4、htly bonded oxide that defies removal bychemical or ordinary mechanical means. In many such cases,corrosion rates are established by mass gain rather than massloss.)1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of th

5、e user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificprecautionary statements, see 1 and 7.2.2. Referenced Documents2.1 ASTM Standards:A 262 Practices for Detecting Susceptibility to Intergr

6、anu-lar Attack in Austenitic Stainless Steels2D 1193 Specification for Reagent Water3D 1384 Test Method for Corrosion Test for Engine Coolantsin Glassware4D 2776 Test Methods for Corrosivity of Water in the Ab-sence of Heat Transfer (Electrical Methods)5G15 Terminology Relating to Corrosion and Corr

7、osionTesting6G16 Guide forApplying Statistics toAnalysis of CorrosionData6G31 Practice for Laboratory Immersion Corrosion Testingof Metals6G33 Practice for Recording Data from Atmospheric Cor-rosion Tests of Metallic-Coated Steel Specimens6G46 Guide for Examination and Evaluation of PittingCorrosion

8、6G50 Practice for Conducting Atmospheric Corrosion Testson Metals6G78 Guide for Crevice Corrosion Testing of Iron Base andNickel-Base Stainless Alloys in Seawater and OtherChloride-Containing Aqueous Environments63. Terminology3.1 See Terminology G15for terms used in this practice.4. Significance an

9、d Use4.1 The procedures given are designed to remove corrosionproducts without significant removal of base metal. This allowsan accurate determination of the mass loss of the metal or alloythat occurred during exposure to the corrosive environment.4.2 These procedures, in some cases, may apply to me

10、talcoatings. However, possible effects from the substrate must beconsidered.5. Reagents and Materials5.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagen

11、ts of the American Chemical Society wheresuch specifications are available.7Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.5.2 Purity of WaterUnless otherwise indicated, ref

12、erencesto water shall be understood to mean reagent water as definedby Type IV of Specification D 1193.1This practice is under the jurisdiction of ASTM Committee G01 on Corrosionof Metals and is the direct responsibility of Subcommittee G01.05 on LaboratoryCorrosion Tests.Current edition approved Oc

13、tober 1, 2003. Published October 2003. Originallyapproved in 1967. Last previous edition approved in 1999 as G190(1999)e1.2Annual Book of ASTM Standards, Vol 01.03.3Annual Book of ASTM Standards, Vol 11.01.4Annual Book of ASTM Standards, Vol 15.05.5Discontinued, replaced by Guide G 96. See 1990 Annu

14、al Book of ASTMStandards, Vol 03.02.6Annual Book of ASTM Standards, Vol 03.02.7Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for Labora

15、toryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Methods for Preparing

16、 Specimens for Test6.1 For laboratory corrosion tests that simulate exposure toservice environments, a commercial surface, closely resem-bling the one that would be used in service, will yield the mostmeaningful results.6.2 It is desirable to mark specimens used in corrosion testswith a unique desig

17、nation during preparation. Several tech-niques may be used depending on the type of specimen andtest.6.2.1 Stencil or StampMost metallic specimens may bemarked by stenciling, that is, imprinting the designation codeinto the metal surface using hardened steel stencil stamps hitwith a hammer. The resu

18、lting imprint will be visible even aftersubstantial corrosion has occurred. However, this procedureintroduces localized strained regions and the possibility ofsuperficial iron contamination in the marked area.6.2.2 Electric engraving by means of a vibratory markingtool may be used when the extent of

19、 corrosion damage isknown to be small. However, this approach to marking is muchmore susceptible to having the marks lost as a result ofcorrosion damage during testing.6.2.3 Edge notching is especially applicable when extensivecorrosion and accumulation of corrosion products is antici-pated. Long te

20、rm atmospheric tests and sea water immersiontests on steel alloys are examples where this approach isapplicable. It is necessary to develop a code system when usingedge notches.6.2.4 Drilled holes may also be used to identify specimenswhen extensive metal loss, accumulation of corrosion products,or

21、heavy scaling is anticipated. Drilled holes may be simplerand less costly than edge notching. A code system must bedeveloped when using drilled holes. Punched holes should notbe used as they introduce residual strain.6.2.5 When it is undesirable to deform the surface ofspecimens after preparation pr

22、ocedures, for example, whentesting coated surfaces, tags may be used for specimen identi-fication. A metal or plastic wire can be used to attach the tag tothe specimen and the specimen identification can be stampedon the tag. It is important to ensure that neither the tag nor thewire will corrode or

23、 degrade in the test environment. It is alsoimportant to be sure that there are no galvanic interactionsbetween the tag, wire, and specimen.6.3 For more searching tests of either the metal or theenvironment, standard surface finishes may be preferred. Asuitable procedure might be:6.3.1 Degrease in a

24、n organic solvent or hot alkaline cleaner.(See also Practice G31.)NOTE 1Hot alkalies and chlorinated solvents may attack some metals.NOTE 2Ultrasonic cleaning may be beneficial in both pre-test andpost-test cleaning procedures.6.3.2 Pickle in an appropriate solution if oxides or tarnishare present.

25、In some cases the chemical cleaners described inSection 6 will suffice.NOTE 3Pickling may cause localized corrosion on some materials.6.3.3 Abrade with a slurry of an appropriate abrasive or withan abrasive paper (see Practices A 262 and Test MethodD 1384). The edges as well as the faces of the spec

26、imensshould be abraded to remove burrs.6.3.4 Rinse thoroughly, hot air dry, and store in desiccator.6.4 When specimen preparation changes the metallurgicalcondition of the metal, other methods should be chosen or themetallurgical condition must be corrected by subsequent treat-ment. For example, she

27、aring a specimen to size will cold workand may possibly fracture the edges. Edges should be ma-chined.6.5 The clean, dry specimens should be measured andweighed. Dimensions determined to the third significant figureand mass determined to the fifth significant figure are sug-gested. When more signifi

28、cant figures are available on themeasuring instruments, they should be recorded.7. Methods for Cleaning After Testing7.1 Corrosion product removal procedures can be dividedinto three general categories: mechanical, chemical, and elec-trolytic.7.1.1 An ideal procedure should remove only corrosionprod

29、ucts and not result in removal of any base metal. Todetermine the mass loss of the base metal when removingcorrosion products, replicate uncorroded control specimensshould be cleaned by the same procedure being used on the testspecimen. By weighing the control specimen before and aftercleaning, the

30、extent of metal loss resulting from cleaning canbe utilized to correct the corrosion mass loss.NOTE 4It is desirable to scrape samples of corrosion products beforeusing any chemical techniques to remove them. These scrapings can thenbe subjected to various forms of analyses, including perhaps X-rayd

31、iffraction to determine crystal forms as well as chemical analyses to lookfor specific corrodants, such as chlorides. All of the chemical techniquesthat are discussed in Section 7 tend to destroy the corrosion products andthereby lose the information contained in these corrosion products. Caremay be

32、 required so that uncorroded metal is not removed with thecorrosion products.7.1.2 The procedure given in 7.1.1 may not be reliable whenheavily corroded specimens are to be cleaned. The applicationof replicate cleaning procedures to specimens with corrodedsurfaces will often, even in the absence of

33、corrosion products,result in continuing mass losses. This is because a corrodedsurface, particularly of a multiphase alloy, is often moresusceptible than a freshly machined or polished surface tocorrosion by the cleaning procedure. In such cases, thefollowing method of determining the mass loss due

34、to thecleaning procedure is preferred.7.1.2.1 The cleaning procedure should be repeated on speci-mens several times. The mass loss should be determined aftereach cleaning by weighing the specimen.7.1.2.2 The mass loss should be graphed as a function of thenumber of equal cleaning cycles as shown in

35、Fig. 1. Two lineswill be obtained: AB and BC. The latter will correspond tocorrosion of the metal after removal of corrosion products. Themass loss due to corrosion will correspond approximately topoint B.7.1.2.3 To minimize uncertainty associated with corrosionof the metal by the cleaning method, a

36、 method should bechosen to provide the lowest slope (near to horizontal) of lineBC.G10327.1.3 Repeated treatment may be required for completeremoval of corrosion products. Removal can often be con-firmed by examination with a low power microscope (forexample, 73 to 303). This is particularly useful

37、with pittedsurfaces when corrosion products may accumulate in pits. Thisrepeated treatment may also be necessary because of therequirements of 7.1.2.1. Following the final treatment, thespecimens should be thoroughly rinsed and immediately dried.7.1.4 All cleaning solutions shall be prepared with wa

38、terand reagent grade chemicals.7.2 Chemical procedures involve immersion of the corro-sion test specimen in a specific solution that is designed toremove the corrosion products with minimal dissolution of anybase metal. Several procedures are listed in Table A1.1. Thechoice of chemical procedure to

39、be used is partly a matter oftrial and error to establish the most effective method for aspecific metal and type of corrosion product scale.(WarningThese methods may be hazardous to personnel).7.2.1 Chemical cleaning is often preceded by light brushing(non metallic bristle) or ultrasonic cleaning of

40、 the test speci-men to remove loose, bulky corrosion products.7.2.2 Intermittent removal of specimens from the cleaningsolution for light brushing or ultrasonic cleaning can oftenfacilitate the removal of tightly adherent corrosion products.7.2.3 Chemical cleaning is often followed by light brushing

41、or ultrasonic cleaning in reagent water to remove looseproducts.7.3 Electrolytic cleaning can also be utilized for removal ofcorrosion products. Several useful methods for corrosion testspecimens of iron, cast iron, or steel are given in Table A2.1.7.3.1 Electrolytic cleaning should be preceded by b

42、rushingor ultrasonic cleaning of the test specimen to remove loose,bulky corrosion products. Brushing or ultrasonic cleaningshould also follow the electrolytic cleaning to remove anyloose slime or deposits. This will help to minimize anyredeposition of metal from reducible corrosion products thatwou

43、ld reduce the apparent mass loss.7.4 Mechanical procedures can include scraping, scrubbing,brushing, ultrasonic cleaning, mechanical shocking, and im-pact blasting (for example, grit blasting, water-jet blasting, andso forth). These methods are often utilized to remove heavilyencrusted corrosion pro

44、ducts. Scrubbing with a nonmetallicbristle brush and a mild abrasive-distilled water slurry can alsobe used to remove corrosion products.7.4.1 Vigorous mechanical cleaning may result in the re-moval of some base metal; therefore, care should be exercised.These should be used only when other methods

45、fail to provideadequate removal of corrosion products. As with other meth-ods, correction for metal loss due to the cleaning method isrecommended. The mechanical forces used in cleaning shouldbe held as nearly constant as possible.8. Assessment of Corrosion Damage8.1 The initial total surface area o

46、f the specimen (makingcorrections for the areas associated with mounting holes) andthe mass lost during the test are determined. The averagecorrosion rate may then be obtained as follows:Corrosion Rate 5 K 3 W!/A 3 T 3 D! (1)where:K = a constant (see 8.1.2),T = time of exposure in hours,A = area in

47、cm2,W = mass loss in grams, andD = density in g/cm3(see Appendix X1).8.1.1 Corrosion rates are not necessarily constant with timeof exposure. See Practice G31for further guidance.8.1.2 Many different units are used to express corrosionrates. Using the units in 7.1 for T, A, W, and D, the corrosionra

48、te can be calculated in a variety of units with the followingappropriate value of K:Corrosion Rate Units DesiredConstant (K) in CorrosionRate Equationmils per year (mpy) 3.45 3 106inches per year (ipy) 3.45 3 103inches per month (ipm) 2.87 3 102millimetres per year (mm/y) 8.76 3 104micrometres per y

49、ear (um/y) 8.76 3 107picometres per second (pm/s) 2.78 3 106grams per square meter per hour (g/m2h) 1.00 3 1043 Dmilligrams per square decimeter per day (mdd) 2.40 3 1063 Dmicrograms per square meter per second (g/m2s) 2.78 3 1063 DNOTE 5If desired, these constants may also be used to convertcorrosion rates from one set of units to another. To convert a corrosion ratein units X to a rate in units Y, multiply by KY/KX; for example:15 mpy 5 15 3 2.78 3 106!/3.45 3 106! pm/s (2)8.1.3 In the case of sacrificial alloy coatings for which thereis preferential corrosion of a comp