Standard Practice for Microetching Metals and Alloys

1 Designation: E 407 99 Standard Practice forMicroetching Metals and Alloys1 This 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 indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or Standard has been approved for use by agencies of the Department of This Practice covers chemical solutions and proceduresto be used in etching Metals and Alloys for microscopicexamination. Safety precautions and miscellaneous informa-tion are also 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 safety and health practices and determine the applica-bility of regulatory limitations prior to specificcautionary statements, Referenced Standards:D 1193 Specification for Reagent Water2E7 Terminology Relating to Metallography33.

2 For definition of terms used in this Standard , of Terms Specific to This etch an immersion etchant that produces colorcontrast, often selective to a particular constituent in themicrostructure, 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 a88stainetch ). interference layer method a tech-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 Pepperhoffmethod ).4. Summary of 1is an alphabetical listing of the Metals (includingrare earths) and their Alloys for which etching information isavailable.

3 For each metal and alloy, one or more etchantnumbers and their corresponding use is indicated. Alloys arelisted as a group 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 areitalicizedto differentiate them from nonelectrolytic 2is a numerical listing of all the etchantsreferenced inTable 1and includes the composition and generalprocedure to be followed for each To use the tables, look up the metal or alloy of interestinTable 1and note the etchant numbers corresponding to theresults desired. The etchant composition and procedure is thenlocated inTable 2corresponding to the etchant If the common name of an etchant is known (Marble s,Vilella s, etc.), and it is desired to know the composition,Table3contains an alphabetical listing of etchant names, each codedwith a number corresponding to the etchant composition giveninTable Significance and This Practice lists recommended methods and solutionsfor the etching of specimens for metallographic are listed to highlight phases present in most majoralloy Safety 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.

4 Users should be aware of the typeof hazards involved in the use of all chemicals used, includingthose hazards that are immediate, long-term, visible, invisible,and with or without Consult the product labels and MSDSs for recommen-dations concerning proper protective Practice is under the jurisdiction of ASTM Committee E-4 on Metallog-raphy and is the direct responsibility of Subcommittee on Sampling,Specimen Preparation, and edition approved October 10, 1999. Published November Book of ASTM Standards, Vol Book of ASTM Standards, Vol ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United : This Standard has either been superseded and replaced by a new version or ASTM International ( ) for the latest information Copyright by ASTM Int'l (all rights reserved); Mon Apr 6 16:23:56 EDT 2015 Downloaded/printed by(USP) Universidade de Sao Paulo ((USP) Universidade de Sao Paulo) pursuant to License Agreement.

5 No further reproductions 1 Etchants for MetalsNOTE1 Electrolytic etchants Base:Pure Al1a, 2, 3general structure4, 5grain structure under polarized light1bgrain boundaries and slip lines1000 series1a, 3, 2general structure4, 5grain structure under polarized light6, 7phase identifications2000 series3, 2, 1ageneral structure8a, 6, 7phase identifications3000 series3, 1ageneral structure4, 5grain structure under polarized light8a, 6, 7phase identifications4000 series3, 1ageneral structure5000 series3, 1a, 2, 6, 8ageneral structure4, 5grain structure under polarized light6000 series3, 1a, 2, 6, 8a, 222general structure4, 5grain structure under polarized light1a, 2, 7, 6, 8aphase identifications7000 series3, 1a, 2general structure4, 5grain structure under polarized light3b, 6phase identificationsBeryllium Base:Pure Be9, 10general structure via polarized lightBe alloys11general structureChromium Base:12,13cgeneral structureCobalt Base:Pure Co14, 15, 16, 17general structureHard-facing and tool metals18, 19, 20general structureHigh-temperature alloys20, 18, 16, 21, 22b, 24, 25general structure19phase identificationColumbium Base(see niobium base)Copper Base.

6 Pure Cu26, 27, 28, 29, 30, 31d, 32, 33, 34b, 35,general structure36, 37, 38, 39, 40, 41, 42,8b, 210, 21543, 28chemical polish and etchCu-Al (aluminum bronze)44, 31d, 34b, 35, 36, 37, 38, 39, 40,general structure45, 215Cu-Be46, 41, 45general structureCu-Cr41general structureCu-Mn41general structureCu-Ni34, 47, 48, 40, 49, 50general structureCu-Si41general structureCu-Sn (tin bronze)51, 52general structureAdmiralty metal8bgeneral structureGilding metalCartridge brassFree-cutting brassNickel silver31d, 32, 33, 41, 42, 49general structureCu alloys26, 27, 28, 29, 30, 44, 41, 31d, 32, 33,general structure34b, 35, 36, 37, 38, 39, 210, 21553, 43, 28,49chemical polish and etch42,49, 210darkens beta in alpha-beta brass54etching of cold worked brassDysprosium Base:55, 56general structureErbium Base:55, 56general structureE407 992 Copyright by ASTM Int'l (all rights reserved); Mon Apr 6 16:23:56 EDT 2015 Downloaded/printed by(USP) Universidade de Sao Paulo ((USP) Universidade de Sao Paulo) pursuant to License Agreement.

7 No further reproductions 1 ContinuedMetalEtchantsUsesGadolinium Base:55, 56, 57general structureGermanium Base:58, 59, 60general structureGold Base:Pure Au61, 62general structure63chemical polish and etchAu alloys64b, 62general structure63chemical polish and etch>90 % noble metals61general structure<90 % noble metals65general structureHafnium base:66,67, 68, 69, 70general structure71grain structure under polarized light72chemical polish and etchHolmium Base:55, 56general structureIridium Base:73cgeneral structureIron Base:Pure Fe74agrain boundaries75substructure210colors ferrite grainsFe + C76, 74a, 77, 78, 79general structureand74a, 77, 31a, 223ferrite grain boundariesFe + <1C + <4 % additions80, 81, 82prior austenitic grain boundaries in martensitic andbainitic steels78, 222auntempered martensite31b, 78carbides and phosphides (matrix darkened, carbidesand phosphides remain bright)83cementite attacked rapidly, sustenite less, ferrite andiron phosphide least84overheating and burning85stains carbides86chemical polish-etch210, 211colors ferrite213, 214colors carbides216colors lath martensite in low-carbon high-alloy grades222bfor dual phase steels.

8 Reveals pearlite, darkensmartensite and outlines austeniteFe + 4 12 Cr80, 87, 88, 89, 90, 91, 79, 210general structure86chemical polish-etchFe + 12 30 Cr + <6 Ni (400 Series)80, 87, 88, 89, 34, 40, 92,93, 94, 95, 91, 226general structure96, 97, 98signs phase31ccarbides86chemical polish-etch219grain boundary etch220darkens delta ferriteFe + 12 20 Cr + 4 10 Ni + <7 %80,31c, 89, 99, 100, 91general structureother elements (controlled trans-31ccarbidesformation, precipitation harden-86chemical polish-etching, stainless maraging Alloys )220darkens delta ferriteFe + 15 30 Cr + 6 40 Ni + <5 %13b, 89, 87, 88,83a, 80, 94, 95, 91,general structureother elements (300 Series)101, 212, 221, 22613a, 102, 31c, 48c, 213carbides and sensitizationand48, 96, 97, 98stains sigma phaseFe + 16 25 Cr + 3 6 Ni + 5 10103, 104, 98delineates sigma phase andMn (200 series)103, 104welds of dissimilar metals86chemical polish-etch219grain boundary etch (no twins)220darkens delta ferriteHigh temperature89, 25, 105, 106,97, 212, 221general structure107,108, 213g8precipitate86chemical polish-etchNonstainless maraging steels109, 89, 99, 100, 221general structure83bgrain boundaries86chemical polish-etchE407 993 Copyright by ASTM Int'l (all rights reserved); Mon Apr 6 16:23:56 EDT 2015 Downloaded/printed by(USP) Universidade de Sao Paulo ((USP) Universidade de Sao Paulo) pursuant to License Agreement.

9 No further reproductions 1 ContinuedMetalEtchantsUsesTool steels74a, 80, 14general structure110grain boundaries in tempered tool steel210, 211colors ferrite, lower alloy grades214, 214colors cementite224, 225carbides attacked and coloredSuperalloys86, 87, 94, 221, 226general etch111general structure111g8depletionLead Base:Pure Pb57, 112general structure113for alternate polishing and etchingPb + <2 Sb114, 115, 57, 74bgeneral structure113for alternate polishing and etchingPb + >2 Sb114, 57, 74bgeneral structure113for alternate polishing and etchingPb + Ca112general structure113for alternate polishing and etchingPb alloys116, 117bgeneral structureBabbitt74bgeneral structureMagnesium Base:Pure Mg118, 119, 74a, 120, 121, 122general structure123stain-free polish-etchMg-Mn119, 74a, 124, 122general structureMg-Al, Mg-Al-Zn (Al + Zn <5 %)118, 119, 74a, 125, 124,123, 122general structure120, 125, 126, 127phase identification124, 126, 127grain structureMg-Al, Mg-Al-Zn (Al + Zn >5 %)118, 119, 74a, 125, 124, 121, 122general structure120, 125, 126, 127phase identificationMg-Zn-Zr118, 119, 74a, 1d, 128, 124, 126,general structureand127, 121, 122Mg-Zn-Th-Zr120, 121phase identificationMg-Th-Zr118, 119, 74a, 1d, 124, 127, 121, 122general structureandMg-Rare Earth-Zr120, 121phase identificationMolybdenum Base:98c, 129, 130,131general structureAs cast132achemical polish prior to etchingNickel Base.

10 Pure Ni and high Ni alloys133, 134, 47, 135, 136, 25, 108, 31cgeneral structure137grain boundary sulfidationNi-Ag38, 138, 50, 139general structureNi-Al50, 140, 141,142, 89, 143general structureNi-Cr144, 50,83, 134, 145, 98, 146, 147,13ageneral structureNi-Cu38, 138, 50, 133, 140, 25,134, 47,general structure48b, 94,108,34Ni-Fe50, 140, 141,83, 134, 148, 40, 107, 149general structure74e, 25, 150orientation pittingNi-Mn74egeneral structureNi-Mo143general structureNi-Ti143, 151, 50, 133general structureNi-Zn152general structureSuperalloys94, 105, 138, 153, 12, 87, 89, 212, 226general structure25, 94grain size107, 111,13areveals microstructural inhomogeneity133grain boundary sulfidation154fine precipitation structure19b, 155, 156differential matrix and nonmetallic staining22afor passive Alloys (for example, UNS Alloy N06625)157specific for UNS Alloy N10004107submicroscopic structure in aged super- Alloys particu-larly for electron microscopy.