1、Designation: E 407 07Standard Practice forMicroetching Metals and Alloys1This standard is issued under the fixed designation E 407; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses
2、indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This practice covers chemical solutions and proceduresto be used in etching
3、 metals and alloys for microscopicexamination. Safety precautions and miscellaneous informa-tion are also included.1.2 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 standard to establish appro-priate
4、safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificcautionary statements, see 6.1 and Table 2.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterE7 Terminology Relating to MetallographyE 2014 Guide on Metallo
5、graphic Laboratory Safety3. Terminology3.1 Definitions:3.1.1 For definition of terms used in this standard, seeTerminology E7.3.2 Definitions of Terms Specific to This Standard:3.2.1 tint etchan immersion etchant that produces colorcontrast, often selective to a particular constituent in themicrostr
6、ucture, due to a thin oxide, sulfide, molybdate, chro-mate or elemental selenium film on the polished surface thatreveals the structure due to variations in light interferenceeffects as a function of the film thickness (also called a 88stainetch”).3.2.2 vapor-deposition interference layer method a t
7、ech-nique for producing enhanced contrast between microstructuralconstituents, usually in color, by thin films formed by vacuumdeposition of a dielectric compound (such as ZnTe, ZnSe,TiO2, ZnS or ZnO) with a known index of refraction, generallydue to light interference effects (also known as the “Pe
8、pperhoffmethod”).4. Summary of Practice4.1 Table 1 is an alphabetical listing of the metals (includ-ing rare earths) and their alloys for which etching informationis available. For each metal and alloy, one or more etchantnumbers and their corresponding use is indicated. Alloys arelisted as a group
9、or series when one or more etchants arecommon to the group or series. Specific alloys are listed onlywhen necessary. When more than one etchant number is givenfor a particular use, they are usually given in order ofpreference. The numbers of electrolytic etchants are italicizedto differentiate them
10、from nonelectrolytic etchants.4.2 Table 2 is a numerical listing of all the etchants refer-enced in Table 1and includes the composition and generalprocedure to be followed for each etchant.4.3 To use the tables, look up the metal or alloy of interestin Table 1 and note the etchant numbers correspond
11、ing to theresults desired. The etchant composition and procedure is thenlocated in Table 2corresponding to the etchant number.4.4 If the common name of an etchant is known (Marbles,Vilellas, etc.), and it is desired to know the composition,Table 3contains an alphabetical listing of etchant names, ea
12、chcoded with a number corresponding to the etchant compositiongiven in Table 2.5. Significance and Use5.1 This practice lists recommended methods and solutionsfor the etching of specimens for metallographic examination.Solutions are listed to highlight phases present in most majoralloy systems.6. Sa
13、fety Precautions6.1 Before using or mixing any chemicals, all product labelsand pertinent Material Safety Data Sheets (MSDS) should beread and understood concerning all of the hazards and safetyprecautions to be observed. Users should be aware of the typeof hazards involved in the use of all chemica
14、ls used, includingthose hazards that are immediate, long-term, visible, invisible,1This practice is under the jurisdiction of ASTM Committee E04 on Metallog-raphy and is the direct responsibility of Subcommittee E04.01 on SpecimenPreparation.Current edition approved May 1, 2007. Published May 2007.
15、Originallyapproved in 1999. Last previous edition approved in 1999 as E 407992For 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 ont
16、he ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.and with or without odors. See Guide E 2014 on Metallo-graphic Laboratory Safety for additional information on;Chemical Safety, Electrolytic Polishing/Etching and Labora
17、-tory Ventilation/Fume Hoods.6.1.1 Consult the product labels and MSDSs for recommen-dations concerning proper protective clothing.6.1.2 All chemicals are potentially dangerous. All personsusing any etchants should be thoroughly familiar with all of thechemicals involved and the proper procedure for
18、 handling,mixing, and disposing of each chemical, as well as anycombinations of those chemicals. This includes being familiarwith the federal, state, and local regulations governing thehandling, storage, and disposal of these chemical etchants.6.2 Some basic suggestions for the handling and disposin
19、gof etchants and their ingredients are as follows:6.2.1 When pouring, mixing, or etching, always use theproper protective equipment, (glasses, gloves, apron, etc.) andit is strongly recommended to always work under a certifiedand tested fume hood. This is imperative with etchants thatgive off noxiou
20、s odors or toxic vapors that may accumulate orbecome explosive. In particular, note that solutions containingperchloric acid must be used in an exclusive hood equippedwith a wash down feature to avoid accumulation of explosiveperchlorates. See Guide E 2014 on Metallographic LaboratorySafety for addi
21、tional information on safety precautions forelectrolytes containing perchloric acid6.2.2 No single type of glove will protect against allpossible hazards. Therefore, a glove must be carefully selectedand used to ensure that it will provide the needed protection forthe specific etchant being used. In
22、 some instances it may benecessary to wear more than one pair of gloves to provideproper protection. Information describing the appropriate glovemay be obtained by consulting the MSDS for the chemicalbeing used. If that does not provide enough detailed informa-tion, contact the chemical manufacturer
23、 directly. Additionally,one can contact the glove manufacturer or, if available, consultthe manufacturers glove chart. If the chemical is not listed or ifchemical mixtures are being used, contact the glove manufac-turer for a recommendation.6.2.3 Use proper devices (glass or plastic) for weighing,mi
24、xing, containing, and storage of solutions. A number ofetchants generate fumes or vapors and should only be stored inproperly vented containers. Storage of fuming etchants insealed or non-vented containers may create an explosionhazard.6.2.4 When mixing etchants, always add reagents to thesolvent un
25、less specific instructions indicate otherwise.6.2.5 When etching, always avoid direct physical contactwith the etchant and specimen; use devices such as tongs tohold the specimen (and tufts of cotton, if used).6.2.6 Methanol is a cumulative poison hazard. Where etha-nol or methanol, or both are list
26、ed as alternates, ethanol is thepreferred solvent. Methanol should be used in a properlydesigned chemical fume hood.6.2.7 When working with HF always be sure to wear theappropriate gloves, eye protection and apron. Buying HF at thelowest useable concentration will significantly reduce risk.Additiona
27、lly, it is recommended that a calcium gluconatecream or other appropriate HF neutralizing agent be availablefor use if direct skin contact of the etchant occurs.6.2.8 The EPA states that human studies have clearlyestablished that inhaled chromium (VI) is a human carcinogen,resulting in an increased
28、risk of lung cancer. Animal studieshave shown chromium (VI) to cause lung tumors via inhalationexposure. Therefore, when working with Cr(VI) compoundssuch as K2Cr2O7and CrO3always use a certified and testedfume hood. Additional information can be obtained at the EPAwebsite3.6.2.9 For safety in trans
29、portation, picric acid is distributedby the manufacturer wet with greater than 30% water. Caremust be taken to keep it moist because dry picric acid is shocksensitive and highly explosive especially when it is combinedwith metals such as copper, lead, zinc, and iron. It will alsoreact with alkaline
30、materials including plaster and concrete toform explosive compounds. It should be purchased in smallquantities suitable for use in six to twelve months and checkedperiodically for lack of hydration. Distilled water may beadded to maintain hydration, It must only be stored in plastic orglass bottles
31、with nonmetallic lids. If dried particles are notedon or near the lid, submerge the bottle in water to re-hydratethem before opening. It is recommended that any bottle ofpicric acid that appears dry or is of unknown vintage not beopened and that proper emergency personnel be notified.6.2.10 Wipe up
32、or flush any and all spills, no matter howminute in nature.6.2.11 Properly dispose of all solutions that are not identi-fied by composition and concentration.6.2.12 Store, handle and dispose of chemicals according tothe manufacturers recommendations. Observe printed cau-tions on reagent bottles.6.2.
33、13 Information pertaining to the toxicity, hazards, andworking precautions of the chemicals, solvents, acids, bases,etc. being used (such as material safety data sheets, MSDS)should be available for rapid consultation.Aselection of usefulbooks on this subject is given in Refs. (1-11)4.6.2.14 Facilit
34、ies which routinely use chemical etchantsshould have an employee safety training program to insure theemployees have the knowledge to properly handle chemicaletchants.6.2.15 When working with etchants always know where thenearest safety shower, eye-wash station, and emergency tele-phone are located.
35、7. Miscellaneous Information7.1 If you know the trade name of an alloy and need toknow the composition to facilitate the use of Table 1, refer toa compilation such as Ref (12).7.2 Reagent grade chemicals shall be used for all etchants.Unless otherwise indicated, it is intended that all reagentsconfo
36、rm to specifications of the Committee on AnalyticalReagents of the American Chemical Society where suchspecifications are available. Other grades, such as United States3http:/www.epa.gov/ttn/atw/hlthef/chromium.html4The boldface numbers in parentheses refer to the list of references at the endof thi
37、s standard.E407072Pharmacopeia (USP), may be used, provided it is first ascer-tained that the reagent is of sufficiently high purity to permit itsuse without detrimental effect.7.2.1 Unless otherwise indicated, references to water shallbe understood to mean reagent water as defined by Type IV ofspec
38、ification D 1193. Experience has shown that the quality oftap water varies significantly and can adversely affect someetchants.7.3 Methanol is usually available only as absolute methanol.When using this alcohol it is imperative that approximately 5volume % of water is added whenever an etchant compo
39、sitioncalls for 95 % methanol. Some of these etchants will not workat all if water is not present.7.4 For conversion of small liquid measurements, there areapproximately 20 drops/mL.7.5 Etching should be carried out on a freshly polishedspecimen.7.6 Gentle agitation of the specimen or solution durin
40、gimmersion etching will result in a more uniform etch.7.7 The etching times given are only suggested startingranges and not absolute limits.7.8 In electrolytic etching, d-c current is implied unlessindicated otherwise.7.9 Agood economical source of d-c current for small scaleelectrolytic etching is
41、the standard 6-V lantern battery.7.10 In electrolytic etching, the specimen is the anodeunless indicated otherwise.7.11 Do not overlook the possibility of multiple etchingwith more than one solution in order to fully develop thestructure of the specimen.7.12 Microscope objectives can be ruined by ex
42、posure tohydrofluoric acid fumes from etchant residue inadvertently lefton the specimen. This problem is very common when thespecimen or mounting media contain porosity and when themounting material (such as Bakelite) does not bond tightly tothe specimen resulting in seepage along the edges of thesp
43、ecimen. In all cases, extreme care should be taken to removeall traces of the etchant by thorough washing and completedrying of the specimen before placing it on the microscopestage.7.13 Tint etchants (13, 14-16) are always used by immer-sion, never by swabbing, as this would inhibit film formation.
44、An extremely high quality polish is required as tint etchantswill reveal remaining polishing damage even if it is not visiblewith bright field illumination.After polishing, the surface mustbe carefully cleaned. Use a polyethylene beaker to contain theetchant if it contains fluorine ions (for example
45、, etchantscontaining ammonium bifluoride, NH4FHF). The specimen isplaced in the solution using tongs, polished face up. Gentlyagitate the solution while observing the polished surface. Aftercoloration begins, allow the solution to settle and remainmotionless. Remove the specimen from the etchant whe
46、n thesurface is colored violet, rinse and dry. A light pre-etch with ageneral-purpose chemical etchant may lead to sharper delinea-tion of the structure after tint etching.7.14 Specimens should be carefully cleaned before use of avapor-deposition interference film (“Pepperhoff”) method (13,14-17). A
47、 light pre-etch, or a slight amount of polishing relief,may lead to sharper delination of the constituents after vapordeposition. The deposition is conducted inside a vacuumevaporator of the type used to prepare replicas for electronmicroscopy. One or several small lumps of a suitable dielectriccomp
48、ound with the desired index of refraction is heated undera vacuum until it evaporates.Avacuum level of 1.3 to 0.013 Pa(103to 105mm Hg) is adequate and the polished surfaceshould be about 1015 cm beneath the device that holds thedielectric compound. Slowly evaporate the lumps and observethe surface o
49、f the specimen. It may be helpful to place thespecimen on a small piece of white paper.As the film thicknessincreases, the surface (and the paper) will become colored withthe color sequence changing in the order yellow, green, red,purple, violet, blue, silvery blue. Stop the evaporation when thecolor is purple to violet, although in some cases, thinner filmswith green or red colors have produced good results.7.15 Metals Handbook (18) provides additional advice onetching solutions and techniques for various alloys.8. Precision and Bias8.1 It is not possible to specify the preci
