ASTM G4-2001(2014) Standard Guide for Conducting Corrosion Tests in Field Applications《用现场设备进行腐蚀试验的标准指南》.pdf

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1、Designation: G4 01 (Reapproved 2014)Standard Guide forConducting Corrosion Tests in Field Applications1This standard is issued under the fixed designation G4; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revisio

2、n. 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 This guide covers procedures for conducting corrosiontests in plant equipment or systems under operating conditionsto evaluate the

3、 corrosion resistance of engineering materials. Itdoes not cover electrochemical methods for determining cor-rosion rates.1.1.1 While intended primarily for immersion tests, generalguidelines provided can be applicable for exposure of testspecimens in plant atmospheres, provided that placement andor

4、ientation of the test specimens is non-restrictive to aircirculation.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use.

5、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. See also 10.4.2.2. Referenced Documents2.1 ASTM Standards:2A262 Practices for Detecting Susceptibility to IntergranularA

6、ttack in Austenitic Stainless SteelsE3 Guide for Preparation of Metallographic SpecimensG1 Practice for Preparing, Cleaning, and Evaluating Corro-sion Test SpecimensG15 Terminology Relating to Corrosion and Corrosion Test-ing (Withdrawn 2010)3G16 Guide for Applying Statistics to Analysis of Corrosio

7、nDataG30 Practice for Making and Using U-Bend Stress-Corrosion Test SpecimensG36 Practice for Evaluating Stress-Corrosion-Cracking Re-sistance of Metals and Alloys in a Boiling MagnesiumChloride SolutionG37 Practice for Use of Mattssons Solution of pH 7.2 toEvaluate the Stress-Corrosion Cracking Sus

8、ceptibility ofCopper-Zinc AlloysG41 Practice for Determining Cracking Susceptibility ofMetals Exposed Under Stress to a Hot Salt EnvironmentG44 Practice for Exposure of Metals andAlloys byAlternateImmersion in Neutral 3.5 % Sodium Chloride SolutionG46 Guide for Examination and Evaluation of Pitting

9、Cor-rosionG47 Test Method for Determining Susceptibility to Stress-Corrosion Cracking of 2XXX and 7XXX AluminumAlloy ProductsG58 Practice for Preparation of Stress-Corrosion Test Speci-mens for WeldmentsG78 Guide for Crevice Corrosion Testing of Iron-Base andNickel-Base Stainless Alloys in Seawater

10、and OtherChloride-Containing Aqueous Environments2.2 NACE Standard:4RP0497 Field Corrosion Evaluation Using Metallic TestSpecimens3. Significance and UseNOTE 1This guide is consistent with NACE Standard RP0497.3.1 Observations and data derived from corrosion testingare used to determine the average

11、rate of corrosion or othertypes of attack, or both (see Terminology G15), that occurduring the exposure interval. The data may be used as part ofan evaluation of candidate materials of construction for use insimilar service or for replacement materials in existing facili-ties.3.2 The data developed

12、from in-plant tests may also be usedas guide lines to the behavior of existing plant materials for thepurpose of scheduling maintenance and repairs.3.3 Corrosion rate data derived from a single exposuregenerally do not provide information on corrosion rate change1This guide is under the jurisdiction

13、 of ASTM Committee G01 on Corrosion ofMetals and is the direct responsibility of Subcommittee G01.14 on Corrosion ofMetals in Construction Materials.Current edition approved Nov. 1, 2014. Published November 2014. Originallyapproved in 1968. Last previous edition approved in 2008 as G401 (2008). DOI:

14、10.1520/G0004-01R14.2For 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 last approved version of this histor

15、ical standard is referenced onwww.astm.org.4Available from NACE International (NACE), 1440 South Creek Dr., Houston,TX 77084-4906, http:/www.nace.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1versus time. Corrosion rates may inc

16、rease, decrease, or remainconstant, depending on the nature of the corrosion products andthe effects of incubation time required at the onset of pitting orcrevice corrosion.4. Limitations4.1 Metal specimens immersed in a specific liquid may notcorrode at the same rate or in the same manner as in equ

17、ipmentin which the metal acts as a heat transfer medium in heating orcooling the liquid. In certain services, the corrosion of heat-exchanger tubes may be quite different from that of the shell orheads. This phenomenon also occurs on specimens exposed ingas streams from which water or other corroden

18、ts condense oncool surfaces. Such factors must be considered in both designand interpretation of plant tests.4.2 Effects caused by high velocity, abrasive ingredients,etc. (which may be emphasized in pipe elbows, pumps, etc.)may not be easily reproduced in simple corrosion tests.4.3 The behavior of

19、certain metals and alloys may beprofoundly influenced by the presence of dissolved oxygen. Itis essential that the test specimens be placed in locationsrepresentative of the degree of aeration normally encounteredin the process.4.4 Corrosion products from the test specimens may haveundesirable effec

20、ts on the process stream and should beevaluated before the test.4.5 Corrosion products from the plant equipment mayinfluence the corrosion of one or more of the test metals. Forexample, when aluminum specimens are exposed in copper-containing systems, corroding copper will exert an adverseeffect on

21、the corrosion of the aluminum. On the contrary,stainless steel specimens may have their corrosion resistanceenhanced by the presence of the oxidizing cupric ions.4.6 The accumulation of corrosion products can sometimeshave harmful effects. For example, copper corroding in inter-mediate strengths of

22、sulfuric acid will have its corrosion rateincreased as the cupric ion concentration in the acid increases.4.7 Tests covered by this guide are predominantly designedto investigate general corrosion; however, other forms ofcorrosion may be evaluated.4.7.1 Galvanic corrosion may be investigated by spec

23、ialdevices that couple one specimen to another in electricalcontact. It should be observed, however, that galvanic corro-sion can be greatly affected by the area ratios of the respectivemetals.4.7.2 Crevice or concentration cell corrosion may occurwhen the metal surface is partially blocked from the

24、 bulkliquid, as under a spacer. An accumulation of bulky corrosionproducts between specimens can promote localized corrosionof some alloys or affect the general corrosion rates of others.Such accumulation should be reported.4.7.3 Selective corrosion at the grain boundaries (forexample, intergranular

25、 corrosion of sensitized austenitic stain-less steels) will not be readily observable in mass lossmeasurements and often requires microscopic examination ofthe specimens after exposure.4.7.4 Parting or dealloying is a condition in which oneconstituent is selectively removed from an alloy, as in thed

26、ezincification of brass or the graphitic corrosion of cast iron.Close attention and a more sophisticated evaluation than asimple mass loss measurement are required to detect thisphenomenon.4.7.5 Pitting corrosion cannot be evaluated by mass loss. Itis possible to miss the phenomenon altogether when

27、usingsmall test specimens since the occurrence of pitting is often astatistical phenomenon and its incidence can be directly relatedto the area of metal exposed.4.7.6 Stress-corrosion cracking (SCC) may occur underconditions of tensile stress and it may or may not be visible tothe naked eye or on ca

28、sual inspection. A metallographicexamination (Practice E3) will confirm this mechanism ofattack. SCC usually occurs with no significant loss in mass ofthe test specimen, except in some refractory metals.4.7.7 A number of reactive metals, most notably titaniumand zirconium, develop strongly adherent

29、corrosion productfilms in corrosive environments. In many cases, there is noacceptable method to remove the film without removingsignificant uncorroded metal. In these cases, the extent ofcorrosion can best be measured as a mass gain rather than massloss.4.7.8 Some materials may suffer accelerated c

30、orrosion atliquid to atmospheric transition zones. The use of small testspecimens may not adequately cover this region.5. Test Specimen Design5.1 Before the size, shape, and finish of test specimens arespecified, the objectives of the test program should bedetermined, taking into consideration any r

31、estrictions thatmight dictate fabrication requirements. The duration, cost,confidence level, and expected results affect the choice of theshape, finish, and cost of the specimen.5.1.1 Test specimens are generally fabricated into disks orrectangular shapes. Other shapes such as balls, cylinders, andt

32、ubes are used, but to a much lesser extent.5.1.2 Disks are normally made by one of three methods: (1)by punching from sheet material, (2) by slicing from a bar, or(3) by trepanning by a lathe or mill. Punched disks are by farthe least expensive and should be considered if materialthickness is not a

33、limitation. Some of the positive characteris-tics of disks are: (1) the surface area can be minimized wherethere is restricted space, such as in pipeline applications, (2)disks can be made inexpensively if a polished or machinedsurface finish is not required, and (3) edge effects are mini-mized for

34、a given total surface area. Some negative character-istics are: (1) disks are very costly to fabricate if a ground finishand machined edges are required, (2) disks fabricated fromsheet material result in a considerable amount of scrapmaterial, and (3) disks sliced from a bar present a surfaceorienta

35、tion that can result in extensive end-grain attack. Usinga bar is undesirable unless end-grain effects are to be evaluated.5.2 Rectangular specimens are fabricated by eitherpunching, shearing, or saw cutting. Punched disk shapedspecimens are the most economical if the quantity is suffi-ciently high

36、to justify the initial die cost. Fabrication is moreG4 01 (2014)2cost-effective for rectangular specimens than for disks whenground finished and machined sides are required, and they canbe made using very few shop tools. In some cases, rectangularspecimens are more awkward to mount.5.3 Material avai

37、lability and machinability also affect thecost of producing all types of specimens. Before the shape andsize are specified, the corrosion engineer should determine thecharacteristics of the proposed materials.6. Test Specimens6.1 The size and shape of test specimens are influenced byseveral factors

38、and cannot be rigidly defined. Sufficient thick-ness should be employed to minimize the possibility ofperforation of the specimen during the test exposure. The sizeof the specimen should be as large as can be convenientlyhandled, the limitation being imposed by the capacity of theavailable analytica

39、l balance and by the problem of effectingentry into operating equipment.6.2 A convenient size for a standard corrosion disk shapedspecimen is 38 mm (1.5 in.) in diameter and 3 mm (0.125 in.)in thickness with an 11 mm (0.438 in.) hole in the center of theround specimen. This size was arrived at as be

40、ing the maxi-mum size that could easily effect entry through a normal 38mm nozzle. However, it is also convenient for larger sizenozzle entries as well as for laboratory corrosion testing. Aconvenient standard specimen for spool-type racks measures25 by 50 by 3 mm (1 by 2 by 0.125 in.) or 50 by 50 b

41、y 3 mm(2 by 2 by 0.125 in.). A round specimen of 53 by 3 mm (2 by0.125 in.) or 55 by 1.5 mm (2 by 0.062 in.) is sometimesemployed. These last three measure about 0.005 dm2in surfacearea.6.3 Other sizes, shapes, and thicknesses of specimens can beused for special purposes or to comply with the design

42、 of aspecial type of corrosion rack. Special designs should bereduced to a few in number in preliminary tests; special designsshould be employed to consider the effect of such factors ofequipment construction and assembly as heat treatment,welding, soldering, and cold-working or other mechanicalstre

43、ssing.6.4 Since welding is a principal method of fabricatingequipment, welded specimens should be included as much aspossible in the test programs.6.4.1 Aside from the effects of residual stresses, the mainitems of interest in a welded specimen are the corrosionresistance of the weld bead and the he

44、at affected zone.Galvanic effects between weld metal and base metal can alsobe evaluated. The weld and heat affected zone regions arerelatively small; therefore, welded specimens should be madeslightly larger than the normal non-welded specimens whenpossible, for example, 50 by 75 mm (2 by 3 in.). T

45、he optimummethod of welding corrosion test specimens is to join the twohalves using a single vee or double vee groove with fullpenetration and multiple passes. Double vee joint preparationis used for very thick samples. Machining the weld flush isoptional, depending on how closely the sample will be

46、 exam-ined afterward (see Practice G58).6.4.2 The welding process and number of passes influencethe heat input and, consequently, the width and location of theheat affected zone. For example, gas tungsten arc welding haslower heat input than oxygen fuel welding and causes anarrower heat affected zon

47、e, which is also closer to the weldbead.7. Preparation of Test Specimens7.1 Controversy exists as to whether the test specimen edgesshould be machined. The cold-worked area caused by shearingor punching operations can provide valuable information onalloy susceptibility to stress corrosion cracking.

48、Also, theability to compare information among specimens of differentmaterials can be affected by the amount of cold work per-formed on the material. Therefore, the decision to machine andto test specimens with/without the residual stresses associatedwith cold work should be made on a case-to-case ba

49、sis.7.1.1 The depth of cold work associated with punching andshearing operations typically extends back from the cut edge toa distance equal to the specimen thickness. Removal of thecold worked areas can be performed by grinding or carefulmachining the specimen edges.7.1.2 Ideally, the surface finish of the specimen shouldreplicate that of the surface finish of the material to be used forequipment fabrication. However, this is often difficult becausethe finish on materials varies between mills, between sheet andplate and even between heat treatments. The mill scale and theamount o