A number in parentheses indicates the year of last reapproval. A superscript 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. Scope 1. Safety precautions and miscellaneous information are also included. 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.
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You are on page 1of 22 Search inside document Standard Practice for Microetching Metals and Alloys1 This standard is issued under the fixed designation E; 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 Department of Defense. Scope 1. Safety precautions and miscellaneous information are also included.
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. Terminology 3. Current edition approved May 1, Published May Originally approved in Last previous edition approved in as E DOI: Summary of Practice 4. 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. The etchant composition and procedure is then located in Table 2corresponding to the etchant number. Solutions are listed to highlight phases present in most major alloy systems.
No further reproductions authorized. E 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. 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. 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 E on Metallographic Laboratory Safety for additional information on safety precautions for electrolytes containing perchloric acid..
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.
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. 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. 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. Animal studies have shown chromium VI to cause lung tumors via inhalation exposure. Additional information can be obtained at the EPA website3.
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. Observe printed cautions on reagent bottles. A selection of useful books on this subject is given in Refs. Miscellaneous Information 7. Unless otherwise indicated, it is intended that all reagents 3 The boldface numbers in parentheses refer to the list of references at the end of this standard.
E 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.
Experience has shown that the quality of tap water varies significantly and can adversely affect some etchants. Some of these etchants will not work at all if water is not present. 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. 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, NH4 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. 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 suitable dielectric compound with the desired index of refraction is heated under a vacuum until it evaporates. A vacuum level of 1. Slowly evaporate the lumps and observe the surface of the specimen. It may be helpful to place the specimen on a small piece of white paper. As the film thickness increases, the surface and the paper will become colored with the color sequence changing in the order yellow, green, red, purple, violet, blue, silvery blue.
Stop the evaporation when the color is purple to violet, although in some cases, thinner films with green or red colors have produced good results. Precision and Bias 8. Keywords 9. NOTE 2Electrolytic etchants are italicized.
Tozil Immerse about 15 s. Brown discoloration will form at edges of specimen. Immerse few seconds to a few minutes. Precaution—Properly discard before solution attains a dark orange color. Pure Mgadtm, 74a,74a,74a,,, 74a,awtm,, 74a, 1d,,, 74a, 1d,, 98c, a general structure stain-free polish-etch general structure general structure phase identi?
ASTM E407 - 07(2015)E1
ASTM E407-07 Standard Practice for Microetching Metals and Alloys