ASTM E340
Full Name
ASTM E340 – Standard Practice for Macroetching Metals and Alloys
Scope
ASTM E340 is a standard practice used to prepare and examine the macroscopic structure of metals and alloys. Macroetching involves chemically or electrolytically etching the surface of a material to reveal its grain structure, porosity, segregation, and other defects.
Etching reagents:
- Chemical etchants: acidic or alkaline solutions that dissolve specific constituents of the material.
- Electrolytic etchants: solutions that use an electric current to selectively remove material from the surface.
Etching techniques:
- Immersion etching: the specimen is completely immersed in the etching solution.
- Spot etching: a small area of the specimen is exposed to the etching solution using a cotton swab or brush.
- Electrolytic etching: the specimen is connected to the negative terminal of a power supply and immersed in an electrolytic solution.
Examination:
- Visual inspection: the etched surface is examined using a magnifying glass or low-power microscope.
- Photography: the etched surface is photographed to document the microstructure.
Applications – macroetching is used in various industries, including:
- Manufacturing: quality control, materials selection, and process monitoring.
- Research and development: material characterization and failure analysis.
- Construction: inspection of structural components and materials.
Resources
Keywords
macroetching; metals; alloys; standard practice; surface preparation; etching reagents; chemical etchants; electrolytic etchants; immersion etching; spot etching; electrolytic etching; examination; visual inspection; photography; quality control; material selection; process monitoring; research and development; manufacturing; construction; inspection; structural components; materials; surface defects; grain structure; porosity; segregation; failure analysis; testing services; ASTM E340