COMMON ETCHANTS
CAUTION:Safety is very important when etching. Be sure to wear the appropriate protective clothing and observe all WARNINGS on chemical manufacuters MSDS. Also review the COMMENTS and CONDITIONS Section for each etchant.
Recommended Etchants
The following table lists the most commonly used etchants
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 |
Guide to Acid Concentrations
Acid / Base |
Specific gravity |
Concentration |
|
Nitric (HNO3) |
1.4 |
68-70% |
Hydrofluoric (HF) |
- |
40% |
Hydrochloric (HCl) |
- |
37-38% |
|
Ammonium Hydroxide |
- |
35% |