Etching
Etching is a process for revealing the structure of the material, common etching techniques include:
- Chemical
- Electrolytic
- Thermal
- Plasma
- Molten salt
- Magnetic
Common Etchants
There are a number of more common etching solutions. Several of them are listed in the folowing table.
Etchant |
Composition |
Conc. |
Conditions |
Comments |
Kalling's No. 1 |
Distilled water |
33 ml |
Immersion etching at 20 degrees Celcius |
For etching martensitic stainless steels. Martensite will be dark and the ferrite will be colored. |
Kalling's No. 2 |
CuCl2 |
5 grams |
Immersion etching at 20 degrees Celcius |
For etching duplex stainless steels and Ni-Cu alloys and superalloys. |
Kellers Etch |
Distilled water |
190 ml |
10-30 second immersion. Use only fresh etchant |
Excellent for aluminum and alloys - immersion for 10-20 seconds ; titanium alloys immersion for 10-20 seconds. |
Kroll’s Reagent |
Distilled water |
92 ml |
15 seconds |
Excellent for titanium and alloys. Swab specimen up to 20 seconds. |
Nital |
Ethanol |
100 ml |
Seconds to minutes |
Most common etchant for Fe, carbon and alloys steels and cast iron - Immerse sample up from seconds to minutes; Mn-Fe, MnNi, Mn-Cu, Mn-Co alloys - immersion up to a few minutes. |
Marble's Reagent |
CuSO4 |
10 grams |
Immerse or swab for |
For etching Ni, Ni-Cu and Ni-Fe alloys and superalloys. Add a few drops of H2SO4 to increase activity. |
Murakami's |
K3Fe(CN)6 |
10 grams |
Pre-mix KOH and water before adding |
Cr and alloys (use fresh and immerse); iron and steels reveals carbides; Mo and alloys uses fresh and immerse; Ni-Cu alloys for alpha phases use at 75 Celcius; W and alloys use fresh and immerse; WC-Co and complex sintered carbides. |
Picral |
Ethanol |
100 ml |
Seconds to minutes |
Recommended for microstructures containing ferrite and carbide. |
Vilella’s Reagent |
Glycerol |
45 ml |
Seconds to minutes |
Good for ferrite-carbide structures (tempered martensite) in iron and steel |
Etchant Database CD
For more specific etchants, PACE Technologies offers an CD etchant database containing over 2200 etchants.
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| Metallographic etchant and training CD | ||
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| Etchant database search result | Metallographic training basics | |
ETCHING PRODUCT DESCRIPTIONS
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ETCHING / SPECIMEN PREPARATION |
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Description |
Quantity |
Catalog Number |
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Etchant / Specimen preparation CD |
each |
CD-ETCH |
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