ASTM E407-07(2015)e1

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: E407 − 07 (Reapproved 2015)
Standard Practice for
Microetching Metals and Alloys
This standard is issued under the fixed designation E407; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
ε NOTE—Originally approved date was editorially corrected to 1970 in footnote 1 in January 2016.
1. Scope 3.2.2 vapor-deposition interference layer method— a tech-
nique for producing enhanced contrast between microstructural
1.1 This practice covers chemical solutions and procedures
constituents, usually in color, by thin films formed by vacuum
to be used in etching metals and alloys for microscopic
deposition of a dielectric compound (such as ZnTe, ZnSe,
examination. Safety precautions and miscellaneous informa-
TiO , ZnS or ZnO) with a known index of refraction, generally
tion are also included.
due to light interference effects (also known as the “Pepperhoff
1.2 This standard does not purport to address all of the
method”).
safety concerns, if any, associated with its use. It is the
4. Summary of Practice
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
4.1 Table 1 is an alphabetical listing of the metals (includ-
bility of regulatory limitations prior to use. For specific
ing rare earths) and their alloys for which etching information
cautionary statements, see 6.1 and Table 2.
is available. For each metal and alloy, one or more etchant
numbers and their corresponding use is indicated. Alloys are
2. Referenced Documents
listed as a group or series when one or more etchants are
common to the group or series. Specific alloys are listed only
2.1 ASTM Standards:
when necessary. When more than one etchant number is given
D1193 Specification for Reagent Water
for a particular use, they are usually given in order of
E7 Terminology Relating to Metallography
preference. The numbers of electrolytic etchants are italicized
E2014 Guide on Metallographic Laboratory Safety
to differentiate them from nonelectrolytic etchants.
3. Terminology
4.2 Table 2 is a numerical listing of all the etchants refer-
enced in Table 1and includes the composition and general
3.1 Definitions:
3.1.1 For definition of terms used in this standard, see procedure to be followed for each etchant.
Terminology E7.
4.3 To use the tables, look up the metal or alloy of interest
3.2 Definitions of Terms Specific to This Standard:
in Table 1 and note the etchant numbers corresponding to the
3.2.1 tint etch—an immersion etchant that produces color
results desired. The etchant composition and procedure is then
contrast, often selective to a particular constituent in the
located in Table 2corresponding to the etchant number.
microstructure, due to a thin oxide, sulfide, molybdate, chro-
4.4 If the common name of an etchant is known (Marble’s,
mate or elemental selenium film on the polished surface that
Vilella’s, etc.), and it is desired to know the composition,
reveals the structure due to variations in light interference
Table 3contains an alphabetical listing of etchant names, each
effects as a function of the film thickness (also called a ''stain
coded with a number corresponding to the etchant composition
etch”).
given in Table 2.
5. Significance and Use
This practice is under the jurisdiction of ASTM Committee E04 on Metallog-
5.1 This practice lists recommended methods and solutions
raphy and is the direct responsibility of Subcommittee E04.01 on Specimen
for the etching of specimens for metallographic examination.
Preparation.
Solutions are listed to highlight phases present in most major
Current edition approved June 1, 2015. Published September 2015. Originally
ɛ1
approved in 1970. Last previous edition approved in 2007 as E407–07 . DOI:
alloy systems.
10.1520/E0407-07R15E01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6. Safety Precautions
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
6.1 Before using or mixing any chemicals, all product labels
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. and pertinent Material Safety Data Sheets (MSDS) should be
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
E407 − 07 (2015)
read and understood concerning all of the hazards and safety 6.2.7 When working with HF always be sure to wear the
precautions to be observed. Users should be aware of the type appropriate gloves, eye protection and apron. Buying HF at the
of hazards involved in the use of all chemicals used, including lowest useable concentration will significantly reduce risk.
those hazards that are immediate, long-term, visible, invisible, Additionally, it is recommended that a calcium gluconate
and with or without odors. See Guide E2014 on Metallographic cream or other appropriate HF neutralizing agent be available
Laboratory Safety for additional information on; Chemical for use if direct skin contact of the etchant occurs.
Safety, Electrolytic Polishing/Etching and Laboratory 6.2.8 The EPA states that human studies have clearly
Ventilation/Fume Hoods. established that inhaled chromium (VI) is a human carcinogen,
6.1.1 Consult the product labels and MSDSs for recommen- resulting in an increased risk of lung cancer. Animal studies
have shown chromium (VI) to cause lung tumors via inhalation
dations concerning proper protective clothing.
exposure. Therefore, when working with Cr(VI) compounds
6.1.2 All chemicals are potentially dangerous. All persons
such as K Cr O and CrO always use a certified and tested
using any etchants should be thoroughly familiar with all of the
2 2 7 3
fume hood. Additional information can be obtained at the EPA
chemicals involved and the proper procedure for handling,
website .
mixing, and disposing of each chemical, as well as any
6.2.9 For safety in transportation, picric acid is distributed
combinations of those chemicals. This includes being familiar
by the manufacturer wet with greater than 30% water. Care
with the federal, state, and local regulations governing the
must be taken to keep it moist because dry picric acid is shock
handling, storage, and disposal of these chemical etchants.
sensitive and highly explosive especially when it is combined
6.2 Some basic suggestions for the handling and disposing
with metals such as copper, lead, zinc, and iron. It will also
of etchants and their ingredients are as follows:
react with alkaline materials including plaster and concrete to
6.2.1 When pouring, mixing, or etching, always use the
form explosive compounds. It should be purchased in small
proper protective equipment, (glasses, gloves, apron, etc.) and
quantities suitable for use in six to twelve months and checked
it is strongly recommended to always work under a certified
periodically for lack of hydration. Distilled water may be
and tested fume hood. This is imperative with etchants that
added to maintain hydration, It must only be stored in plastic or
give off noxious odors or toxic vapors that may accumulate or
glass bottles with nonmetallic lids. If dried particles are noted
become explosive. In particular, note that solutions containing
on or near the lid, submerge the bottle in water to re-hydrate
perchloric acid must be used in an exclusive hood equipped
them before opening. It is recommended that any bottle of
with a wash down feature to avoid accumulation of explosive
picric acid that appears dry or is of unknown vintage not be
perchlorates. See Guide E2014 on Metallographic Laboratory
opened and that proper emergency personnel be notified.
Safety for additional information on safety precautions for
6.2.10 Wipe up or flush any and all spills, no matter how
electrolytes containing perchloric acid.
minute in nature.
6.2.2 No single type of glove will protect against all
6.2.11 Properly dispose of all solutions that are not identi-
possible hazards. Therefore, a glove must be carefully selected
fied by composition and concentration.
and used to ensure that it will provide the needed protection for
6.2.12 Store, handle and dispose of chemicals according to
the specific etchant being used. In some instances it may be
the manufacturer’s recommendations. Observe printed cau-
necessary to wear more than one pair of gloves to provide
tions on reagent bottles.
proper protection. Information describing the appropriate glove
6.2.13 Information pertaining to the toxicity, hazards, and
may be obtained by consulting the MSDS for the chemical
working precautions of the chemicals, solvents, acids, bases,
being used. If that does not provide enough detailed
etc. being used (such as material safety data sheets, MSDS)
information, contact the chemical manufacturer directly.
should be available for rapid consultation. A selection of useful
Additionally, one can contact the glove manufacturer or, if
books on this subject is given in Refs. (1-11) .
available, consult the manufacturers glove chart. If the chemi-
6.2.14 Facilities which routinely use chemical etchants
cal is not listed or if chemical mixtures are being used, contact
should have an employee safety training program to insure the
the glove manufacturer for a recommendation.
employees have the knowledge to properly handle chemical
6.2.3 Use proper devices (glass or plastic) for weighing,
etchants.
mixing, containing, and storage of solutions. A number of
6.2.15 When working with etchants always know where the
etchants generate fumes or vapors and should only be stored in
nearest safety shower, eye-wash station, and emergency tele-
properly vented containers. Storage of fuming etchants in
phone are located.
sealed or non-vented containers may create an explosion
7. Miscellaneous Information
hazard.
6.2.4 When mixing etchants, always add reagents to the
7.1 If you know the trade name of an alloy and need to
solvent unless specific instructions indicate otherwise.
know the composition to facilitate the use of Table 1, refer to
6.2.5 When etching, always avoid direct physical contact
a compilation such as Ref (12).
with the etchant and specimen; use devices such as tongs to
7.2 Reagent grade chemicals shall be used for all etchants.
hold the specimen (and tufts of cotton, if used).
Unless otherwise indicated, it is intended that all reagents
6.2.6 Methanol is a cumulative poison hazard. Where etha-
nol or methanol, or both are listed as alternates, ethanol is the
http://www.epa.gov/ttn/atw/hlthef/chromium.html
preferred solvent. Methanol should be used in a properly 4
The boldface numbers in parentheses refer to the list of references at the end
designed chemical fume hood. of this standard.
´1
E407 − 07 (2015)
conform to specifications of the Committee on Analytical 7.13 Tint etchants (13, 14-16) are always used by
Reagents of the American Chemical Society where such immersion, never by swabbing, as this would inhibit film
specifications are available. Other grades, such as United States formation. An extremely high quality polish is required as tint
Pharmacopeia (USP), may be used, provided it is first ascer- etchants will reveal remaining polishing damage even if it is
tained that the reagent is of sufficiently high purity to permit its not visible with bright field illumination. After polishing, the
use without detrimental effect. surface must be carefully cleaned. Use a polyethylene beaker
7.2.1 Unless otherwise indicated, references to water shall to contain the etchant if it contains fluorine ions (for example,
be understood to mean reagent water as defined by Type IV of etchants containing ammonium bifluoride, NH FHF). The
specification D1193. Experience has shown that the quality of specimen is placed in the solution using tongs, polished face
tap water varies significantly and can adversely affect some up. Gently agitate the solution while observing the polished
etchants. surface. After coloration begins, allow the solution to settle and
remain motionless. Remove the specimen from the etchant
7.3 Methanol is usually available only as absolute methanol.
when the surface is colored violet, rinse and dry. A light
When using this alcohol it is imperative that approximately 5
pre-etch with a general-purpose chemical etchant may lead to
volume % of water is added whenever an etchant composition
sharper delineation of the structure after tint etching.
calls for 95 % methanol. Some of these etchants will not work
at all if water is not present. 7.14 Specimens should be carefully cleaned before use of a
vapor-deposition interference film (“Pepperhoff”) method (13,
7.4 For conversion of small liquid measurements, there are
14-17). A light pre-etch, or a slight amount of polishing relief,
approximately 20 drops/mL.
may lead to sharper delination of the constituents after vapor
7.5 Etching should be carried out on a freshly polished
deposition. The deposition is conducted inside a vacuum
specimen.
evaporator of the type used to prepare replicas for electron
7.6 Gentle agitation of the specimen or solution during
microscopy. One or several small lumps of a suitable dielectric
immersion etching will result in a more uniform etch. compound with the desired index of refraction is heated under
a vacuum until it evaporates. A vacuum level of 1.3 to 0.013 Pa
7.7 The etching times given are only suggested starting
−3 −5
(10 to 10 mm Hg) is adequate and the polished surface
ranges and not absolute limits.
should be about 10–15 cm beneath the device that holds the
7.8 In electrolytic etching, d-c current is implied unless
dielectric compound. Slowly evaporate the lumps and observe
indicated otherwise.
the surface of the specimen. It may be helpful to place the
7.9 A good economical source of d-c current for small scale specimen on a small piece of white paper. As the film thickness
electrolytic etching is the standard 6-V lantern battery.
increases, the surface (and the paper) will become colored with
the color sequence changing in the order yellow, green, red,
7.10 In electrolytic etching, the specimen is the anode
purple, violet, blue, silvery blue. Stop the evaporation when the
unless indicated otherwise.
color is purple to violet, although in some cases, thinner films
7.11 Do not overlook the possibility of multiple etching
with green or red colors have produced good results.
with more than one so
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: E407 − 07 (Reapproved 2015) E407 − 07 (Reapproved 2015)
Standard Practice for
Microetching Metals and Alloys
This standard is issued under the fixed designation E407; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
ε NOTE—Originally approved date was editorially corrected to 1970 in footnote 1.
1. Scope
1.1 This practice covers chemical solutions and procedures to be used in etching metals and alloys for microscopic examination.
Safety precautions and miscellaneous information are also included.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use. For specific cautionary statements, see 6.1 and Table 2.
2. Referenced Documents
2.1 ASTM Standards:
D1193 Specification for Reagent Water
E7 Terminology Relating to Metallography
E2014 Guide on Metallographic Laboratory Safety
3. Terminology
3.1 Definitions:
3.1.1 For definition of terms used in this standard, see Terminology E7.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 tint etch—an immersion etchant that produces color contrast, often selective to a particular constituent in the
microstructure, due to a thin oxide, sulfide, molybdate, chromate or elemental selenium film on the polished surface that reveals
the structure due to variations in light interference effects as a function of the film thickness (also called a ''stain etch”).
3.2.2 vapor-deposition interference layer method— a technique for producing enhanced contrast between microstructural
constituents, usually in color, by thin films formed by vacuum deposition of a dielectric compound (such as ZnTe, ZnSe, TiO , ZnS
or ZnO) with a known index of refraction, generally due to light interference effects (also known as the “Pepperhoff method”).
4. Summary of Practice
4.1 Table 1 is an alphabetical listing of the metals (including rare earths) and their alloys for which etching information is
available. For each metal and alloy, one or more etchant numbers and their corresponding use is indicated. Alloys are listed as a
group or series when one or more etchants are common to the group or series. Specific alloys are listed only when necessary. When
more than one etchant number is given for a particular use, they are usually given in order of preference. The numbers of
electrolytic etchants are italicized to differentiate them from nonelectrolytic etchants.
4.2 Table 2 is a numerical listing of all the etchants referenced in Table 1and includes the composition and general procedure
to be followed for each etchant.
4.3 To use the tables, look up the metal or alloy of interest in Table 1 and note the etchant numbers corresponding to the results
desired. The etchant composition and procedure is then located in Table 2corresponding to the etchant number.
This practice is under the jurisdiction of ASTM Committee E04 on Metallography and is the direct responsibility of Subcommittee E04.01 on Specimen Preparation.
ɛ1
Current edition approved June 1, 2015. Published September 2015. Originally approved in 1999.1970. Last previous edition approved in 2007 as E407–07 . DOI:
10.1520/E0407-07R15.10.1520/E0407-07R15E01.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
´1
E407 − 07 (2015)
4.4 If the common name of an etchant is known (Marble’s, Vilella’s, etc.), and it is desired to know the composition,
Table 3contains an alphabetical listing of etchant names, each coded with a number corresponding to the etchant composition given
in Table 2.
5. Significance and Use
5.1 This practice lists recommended methods and solutions for the etching of specimens for metallographic examination.
Solutions are listed to highlight phases present in most major alloy systems.
6. Safety Precautions
6.1 Before using or mixing any chemicals, all product labels and pertinent Material Safety Data Sheets (MSDS) should be read
and understood concerning all of the hazards and safety precautions to be observed. Users should be aware of the type of hazards
involved in the use of all chemicals used, including those hazards that are immediate, long-term, visible, invisible, and with or
without odors. See Guide E2014 on Metallographic Laboratory Safety for additional information on; Chemical Safety, Electrolytic
Polishing/Etching and Laboratory Ventilation/Fume Hoods.
6.1.1 Consult the product labels and MSDSs for recommendations concerning proper protective clothing.
6.1.2 All chemicals are potentially dangerous. All persons using any etchants should be thoroughly familiar with all of the
chemicals involved and the proper procedure for handling, mixing, and disposing of each chemical, as well as any combinations
of those chemicals. This includes being familiar with the federal, state, and local regulations governing the handling, storage, and
disposal of these chemical etchants.
6.2 Some basic suggestions for the handling and disposing of etchants and their ingredients are as follows:
6.2.1 When pouring, mixing, or etching, always use the proper protective equipment, (glasses, gloves, apron, etc.) and it is
strongly recommended to always work under a certified and tested fume hood. This is imperative with etchants that give off
noxious odors or toxic vapors that may accumulate or become explosive. In particular, note that solutions containing perchloric
acid must be used in an exclusive hood equipped with a wash down feature to avoid accumulation of explosive perchlorates. See
Guide E2014 on Metallographic Laboratory Safety for additional information on safety precautions for electrolytes containing
perchloric acid.
6.2.2 No single type of glove will protect against all possible hazards. Therefore, a glove must be carefully selected and used
to ensure that it will provide the needed protection for the specific etchant being used. In some instances it may be necessary to
wear more than one pair of gloves to provide proper protection. Information describing the appropriate glove may be obtained by
consulting the MSDS for the chemical being used. If that does not provide enough detailed information, contact the chemical
manufacturer directly. Additionally, one can contact the glove manufacturer or, if available, consult the manufacturers glove chart.
If the chemical is not listed or if chemical mixtures are being used, contact the glove manufacturer for a recommendation.
6.2.3 Use proper devices (glass or plastic) for weighing, mixing, containing, and storage of solutions. A number of etchants
generate fumes or vapors and should only be stored in properly vented containers. Storage of fuming etchants in sealed or
non-vented containers may create an explosion hazard.
6.2.4 When mixing etchants, always add reagents to the solvent unless specific instructions indicate otherwise.
6.2.5 When etching, always avoid direct physical contact with the etchant and specimen; use devices such as tongs to hold the
specimen (and tufts of cotton, if used).
6.2.6 Methanol is a cumulative poison hazard. Where ethanol or methanol, or both are listed as alternates, ethanol is the
preferred solvent. Methanol should be used in a properly designed chemical fume hood.
6.2.7 When working with HF always be sure to wear the appropriate gloves, eye protection and apron. Buying HF at the lowest
useable concentration will significantly reduce risk. Additionally, it is recommended that a calcium gluconate cream or other
appropriate HF neutralizing agent be available for use if direct skin contact of the etchant occurs.
6.2.8 The EPA states that human studies have clearly established that inhaled chromium (VI) is a human carcinogen, resulting
in an increased risk of lung cancer. Animal studies have shown chromium (VI) to cause lung tumors via inhalation exposure.
Therefore, when working with Cr(VI) compounds such as K Cr O and CrO always use a certified and tested fume hood.
2 2 7 3
Additional information can be obtained at the EPA website .
6.2.9 For safety in transportation, picric acid is distributed by the manufacturer wet with greater than 30% water. Care must be
taken to keep it moist because dry picric acid is shock sensitive and highly explosive especially when it is combined with metals
such as copper, lead, zinc, and iron. It will also react with alkaline materials including plaster and concrete to form explosive
compounds. It should be purchased in small quantities suitable for use in six to twelve months and checked periodically for lack
of hydration. Distilled water may be added to maintain hydration, It must only be stored in plastic or glass bottles with nonmetallic
lids. If dried particles are noted on or near the lid, submerge the bottle in water to re-hydrate them before opening. It is
recommended that any bottle of picric acid that appears dry or is of unknown vintage not be opened and that proper emergency
personnel be notified.
6.2.10 Wipe up or flush any and all spills, no matter how minute in nature.
http://www.epa.gov/ttn/atw/hlthef/chromium.html
´1
E407 − 07 (2015)
6.2.11 Properly dispose of all solutions that are not identified by composition and concentration.
6.2.12 Store, handle and dispose of chemicals according to the manufacturer’s recommendations. Observe printed cautions on
reagent bottles.
6.2.13 Information pertaining to the toxicity, hazards, and working precautions of the chemicals, solvents, acids, bases, etc.
being used (such as material safety data sheets, MSDS) should be available for rapid consultation. A selection of useful books on
this subject is given in Refs. (1-11) .
6.2.14 Facilities which routinely use chemical etchants should have an employee safety training program to insure the
employees have the knowledge to properly handle chemical etchants.
6.2.15 When working with etchants always know where the nearest safety shower, eye-wash station, and emergency telephone
are located.
7. Miscellaneous Information
7.1 If you know the trade name of an alloy and need to know the composition to facilitate the use of Table 1, refer to a
compilation such as Ref (12).
7.2 Reagent grade chemicals shall be used for all etchants. Unless otherwise indicated, it is intended that all reagents conform
to specifications of the Committee on Analytical Reagents of the American Chemical Society where such specifications are
available. Other grades, such as United States Pharmacopeia (USP), may be used, provided it is first ascertained that the reagent
is of sufficiently high purity to permit its use without detrimental effect.
7.2.1 Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by Type IV of
specification D1193. Experience has shown that the quality of tap water varies significantly and can adversely affect some etchants.
7.3 Methanol is usually available only as absolute methanol. When using this alcohol it is imperative that approximately 5
volume % of water is added whenever an etchant composition calls for 95 % methanol. Some of these etchants will not work at
all if water is not present.
7.4 For conversion of small liquid measurements, there are approximately 20 drops/mL.
7.5 Etching should be carried out on a freshly polished specimen.
7.6 Gentle agitation of the specimen or solution during immersion etching will result in a more uniform etch.
7.7 The etching times given are only suggested starting ranges and not absolute limits.
7.8 In electrolytic etching, d-c current is implied unless indicated otherwise.
7.9 A good economical source of d-c current for small scale electrolytic etching is the standard 6-V lantern battery.
7.10 In electrolytic etching, the specimen is the anode unless indicated otherwise.
7.11 Do not overlook the possibility of multiple etching with more than one solution in order to fully develop the structure of
the specimen.
7.12 Microscope objectives can be ruined by exposure to hydrofluoric acid fumes from etchant residue inadvertently left on the
specimen. This problem is very common when the specimen or mounting media contain porosity and when the mounting material
(such as Bakelite) does not bond tightly to the specimen resulting in seepage along the edges of the specimen. In all cases, extreme
care should be taken to remove all traces of the etchant by thorough washing and complete drying of the specimen before placing
it on the microscope stage.
7.13 Tint etchants (13, 14-16) are always used by immersion, never by swabbing, as this would inhibit film formation. An
extremely high quality polish is required as tint etchants will reveal remaining polishing damage even if it is not visible with bright
field illumination. After polishing, the surface must be carefully cleaned. Use a polyethylene beaker to contain the etchant if it
contains fluorine ions (for example, etchants containing ammonium bifluoride, NH FHF). The specimen is placed in the solution
using tongs, polished face up. Gently agitate the solution while observing the polished surface. After coloration begins, allow the
solution to settle and remain motionless. Remove the specimen from the etchant when the surface is colored violet, rinse and dry.
A light pre-etch with a general-purpose chemical etchant may lead to sharper delineation of the structure after tint etching.
7.14 Specimens should be carefully cleaned before use of a vapor-deposition interference film (“Pepperhoff”) method (13,
14-17). A light pre-etch, or a slight amount of polishing relief, may lead to sharper delination of the constituents after vapor
deposition. The deposition is conducted inside a vacuum evaporator of the type used to prepare replicas for electron microscopy.
One or several small lumps of a suit
...