1、Designation: G 161 00 (Reapproved 2006)Standard Guide forCorrosion-Related Failure Analysis1This standard is issued under the fixed designation G 161; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A num
2、ber in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers key issues to be considered whenexamining metallic failures when corrosion is suspected aseither a major or minor causa
3、tive factor.1.2 Corrosion-related failures could include one or more ofthe following: change in surface appearance (for example,tarnish, rust, color change), pin hole leak, catastrophic struc-tural failure (for example, collapse, explosive rupture, implo-sive rupture, cracking), weld failure, loss o
4、f electrical continu-ity, and loss of functionality (for example, seizure, galling,spalling, swelling).1.3 Issues covered include overall failure site conditions,operating conditions at the time of failure, history of equipmentand its operation, corrosion product sampling, environmentalsampling, met
5、allurgical and electrochemical factors, morphol-ogy (mode) or failure, and by considering the preceding,deducing the cause(s) of corrosion failure.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this sta
6、ndard 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:2E3 Guide for Preparation of Metallographic SpecimensE 1459 Guide for Physical Evidence Labeling and RelatedDocumentationE 149
7、2 Practice for Receiving, Documenting, Storing, andRetrieving Evidence in a Forensic Science LaboratoryG1 Practice for Preparing, Cleaning, and Evaluating Cor-rosion Test SpecimensG46 Guide for Examination and Evaluation of PittingCorrosion3. Significance and Use3.1 This guide is intended to assist
8、those encounteringcorrosion or possible corrosion as a causative factor in a failureanalysis.3.2 This guide is not an absolute plan that will identify thecause of corrosion in all failure analyses.3.3 This guide is intended to help an investigator identifysignificant sources and types of corrosion i
9、nformation that maybe available for failure analysis.3.4 Appendix X1 contains a checklist that is intended toassist in corrosion-related failure evaluations.4. Organizing the Analysis4.1 Early recognition of corrosion as a factor in a failureanalysis is critical to any such investigation. Therefore,
10、 it isgenerally desirable to conduct the analysis as soon as possibleafter the apparent failure. It is always desirable to protect thephysical evidence until the analysis can begin. Much importantcorrosion information can be lost if a failure scene is altered orchanged before appropriate observation
11、s can be made.4.2 A written plan for the detailed analysis should beprepared. The plan may include methods of documentation(photographs before and during analysis, sketches, statements),responsibilities of parties, reporting needs, and scheduling.4.3 If the capability (corrosion knowledge and experi
12、ence)of in-house personnel and availability of resources are inad-equate to make the analysis in a timely manner, it may beexpedient to seek third party services.5. Failure Site Conditions5.1 When possible, an overall examination of the conditionsat a failure site prior to cleaning, moving, or sampl
13、ing debrisshould be conducted. Impressions as to physical arrangements,odors, colors, textures, and conditions of adjacent structurescan provide important clues as to active corrosion processes.5.2 Photographs or videotapes serve as documentation ofthe observations. Color photographs are preferable.
14、 It is helpfulto include labels and indications of size, location, and orienta-tion in the photographs. Photographs before, during, and aftersampling are recommended.5.3 Sketches and drawings with notes as to detailed obser-vations can be beneficial for later evaluations. Locations ofsamples and pho
15、tographs may be shown.1This guide is under the jurisdiction of ASTM Committee G01 on Corrosion ofMetals and is the direct responsibility of Subcommittee G01.05 on LaboratoryCorrosion Tests.Current edition approved Nov. 1, 2006. Published January 2007. Originallyapproved in 1999. Last previous editio
16、n approved in 2000 as G 161 00.2For 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.1Copyright ASTM International,
17、 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.4 Interviews with those who were present or nearby whenthe failure occurred would be appropriate. Information on time,sights, sounds, and conditions can be gained during suchinterviews.6. Operating Conditions At T
18、ime of Failure6.1 Ascertain the operating conditions from operators logs,recorders, and data loggers (verify the accuracy of timerecords). Special attention should be given to the stability ofthe operating conditions, for example, were they stable orvariable. Conditions of corrosion concern could be
19、 tempera-ture, pressure, flow rate, velocity, process stream pH andchemical composition, time, and weather.6.2 Special attention should be given to out-of-specificationor other abnormal or unusual upset conditions.6.3 It may be necessary to plot or track operating conditionsfor an indefinite period
20、of time prior to the detection of failureto more clearly identify any unusual, contributory operatingconditions.6.4 If similar, parallel equipment at the same or otherlocation was operating at the time of the corrosion-relatedfailure, note the operating conditions as a reference point. Suchinformati
21、on could be useful in judging the normalcy of theoperating conditions associated with the failure.6.5 Corrosion monitoring instruments and coupons, ifpresent, should be examined to help document operatingconditions at the time of failure.7. Historical Information7.1 Historical information, when avai
22、lable, is extremelyuseful in understanding some situations. All of the types ofinformation noted may not be useful. Often in cases of olderequipment, historical information may be nearly impossible tofind because of lost files or retired personnel. Based on cost,time, and anticipated benefit, a judg
23、ement must be made as tothe effort one should expend in retrieving historical informa-tion.7.2 Useful details regarding original constructions mayinclude, but are not limited to, design drawings and specifica-tions, material specifications (composition, thermal treatments,surface treatments), joinin
24、g (bolts, rivets, welds, adhesives),and surface treatments (coatings, pickling, etching, anodizing,plating, peening, grinding, insulation, or refractories).7.3 Details regarding modifications made subsequent tooriginal fabrication and prior to the corrosion-related failuremay be extremely important
25、because they often reveal less-than-optimum field work. Modifications may have been madefor one or more reasons, including, but not limited to, problemswith original design, changed service requirements, correctedearlier failures, and correction of safety and environmentalconcerns. The same types of
26、 details suggested in 7.2 should beconsidered regarding modifications.7.4 Details regarding operating history may be important.Three types of operating information that may require docu-mentation are original design parameters, chronology of nomi-nal operating parameters, and anomalous operating par
27、ameters,including out-of-specification periods and significant down-time periods.7.5 Maintenance, cleaning, and repair histories may beimportant and should be documented.7.6 Changes in specification for, and sources of, process rawmaterials and supplies may be significant and should beevaluated.8. S
28、ampling8.1 Careful sampling is critical to the successful investiga-tion of corrosion-related failures. Sampling in corrosion inves-tigations is similar to that used in forensic investigations bycriminologists. Guide E 1459 and Practice E 1492 addressissues of labeling and documenting field evidence
29、. Thesestandards may provide useful guidance during sampling forcorrosion investigations.8.2 The written plan suggested in 4.2 should be supple-mented with a written sampling plan. The plan should specifya sample location, identification system, and method of collec-tion.8.3 Avoid contamination duri
30、ng sampling by using cleantools. Personnel should wear gloves to avoid fingerprints andpersonal contact.8.4 Sample containers should be clean and sealable toprotect samples from contamination and damage. The materialof sample containers should be selected carefully to avoidundesirable interaction wi
31、th samples. Each container should bedated and identified according to the sampling plan.8.5 Samples of corroded and uncorroded materials may beuseful in the identification of causative factors. Samples shouldbe as large as practical to give analysts sufficient material towork with and to protect cri
32、tical corroded areas from damageduring cutting and transporting. If failure initiation location isapparent, it should be sampled. When cutting samples, consid-eration should be given to temperature control and to theintroduction of cutting and cooling fluids that could alter thesurface and metallurg
33、ical conditions. Because of the solubilityin water of many corrosion products, samples must be pro-tected from extraneous moisture.8.6 Corrosion products and deposits should be given specialsampling treatment because they are often key elements inunderstanding the failure. Care should be used in the
34、 selectionof tools for collecting these samples. Nonmetallic tools areoften preferred because they present less chance for contami-nation of the sample or for damaging critical corroded surfaces.When there is insufficient corrosion product or deposit for easyfield sampling, care should be used when
35、handling material sothat subsequent laboratory sampling may be conducted. Be-cause of the solubility in water of many corrosion products,samples must be protected from extraneous moisture.8.7 Process stream samples may be desirable. The mostuseful process stream samples are those taken from the fail
36、urelocation as soon after the event as possible. Delayed or typicalG 161 00 (2006)2process stream samples are less useful because there is noassurance that they represent the conditions at failure.8.8 Special sampling procedures may be required whenmicrobiological factors are suspected of being invo
37、lved. Be-fore taking such samples, consult ASTM STP 1232 for guid-ance (1).38.9 Care should be taken during sampling to protect anyfracture surfaces from becoming damaged. If partial reassem-bly is necessary, maintain an air gap between mating fracturesurfaces. Bringing fracture surfaces together co
38、uld eliminatevery valuable information.9. Evaluation of Samples9.1 Compositions of samples of materials (including fasten-ers and weld beads), process streams, deposits, and corrosionproducts should be determined using appropriate analyticaltools and techniques.9.2 Metallic samples (including fasten
39、ers and weld beads)should be evaluated for metallurgical condition and structure.This evaluation may involve mechanical and physical propertytests, metallographic examination of cross sections, and corro-sion tests.9.2.1 Selection of mechanical and physical property testsshould consider the influenc
40、e of service temperature and timeon the properties being evaluated.9.2.2 Selection of metallographic examination techniquesshould consider the influence of service temperature and timeon the metallurgical structures being examined.9.2.3 Corrosion testing of affected material may be neces-sary to ide
41、ntify metallurgical and environmental factors asso-ciated with the failure. Selection of corrosion tests shouldconsider the suspected type of failure, the materials involved,and the suspected environment.9.2.4 In some cases it may be necessary to remove corrosionproducts to permit evaluation. The gu
42、idance of Practice G1can be used to remove corrosion products with minimaldamage to the metal sample.9.3 Metallic samples are often subdivided into specimenssuitable for laboratory evaluation. The location and orientationof each specimen must be documented by one or more of thefollowing: photographs
43、, drawings, or written descriptions.Each specimen should be labelled to aid in identifying itsoriginal location within the sample.9.4 Failure locations, such as pits, fracture surfaces, crev-ices, and generally attacked surfaces, should be examined, andmeasurements should be made to document surface
44、 chemistry,pit depths, crack dimensions, and metal losses and other modesof attack. These examinations often require the use of lightmicroscopes, scanning electron microscopes (including energydispersive x-ray spectrometers (EDS), and other instruments.In some cases, cross sections from corroded are
45、as may requireexamination (see Methods E3) to relate corrosion extent andmorphology (for example, intergranular or transgranular) tometallurgical structure . In cases involving fracture, fracto-graphic examination is recommended.10. Assessment of Corrosion-Related Failure10.1 Assessment involves the
46、 evaluation of observationsfrom the failure location, operational information, materialsevaluations, examinations of failure samples, and expert opin-ions.10.2 Incorrect or out-of-specification materials, processstreams, and operating conditions should be noted and de-scribed.10.3 Unusual or unexpec
47、ted species in corrosion products ordeposits should be noted and described.10.4 The type and extent of corrosion should be noted. Theextent of corrosion may be determined by measurements andcalculations of general corrosion rate, pitting penetration (seeGuide G46), or crack growth rate. It may also
48、be useful tocompare these rates with expected rates from the literature orexperience. Rate discrepancies should be investigated (forexample, by laboratory simulations). This information will beuseful in judging the suitability of particular materials.10.5 From these observations and findings, the in
49、vestigatorshould be able to identify the one or more causative factor(s)involved in the failure. In many cases, more than one factorwill be suggested as having played a role in the failure.References to similar or related corrosion-related failures areoften useful (2-8). The investigator may provide explanationsand rationales for suggested corrective actions.11. Report11.1 General description of corrosion-related failure.11.2 Operating conditions at time of failure.11.3 Historical information.11.4 Samples taken including photographs.11.5 Evaluations conducted.11.6 Results of evalua
