Etchant |
Composition |
Concentration |
Conditions |
Comments |
Kalling’s No:1 |
Distilled water CuCl2 |
33 ml |
Immersion etching at 20° C |
For etching martensitic stainless steels. Martensite will be dark and the ferrite will be coloured |
HCl |
1,5 grams |
Ethanol |
33 ml |
Kalling’s No:2 |
CuCl2 |
5 grams |
Immersion etching at 20° C |
For etching duplex stainless steels and Ni-Cu alloys and superalloys |
HCl |
100 ml |
Ethanol |
100 ml |
Kellers etch |
Distilled water |
190 ml |
10 –30 seconds immersion. Use only fresh etchant |
Excellent for aluminium and alloys immersion for 10 – 20 seconds; titanium alloys immersion for 10-20 seconds |
Nitric acid |
5 ml |
HCl |
3 ml |
HF |
2 ml |
Kroll’s Reagent |
Distilled water Nitric acid |
92 ml |
15 seconds |
Excellent for titanium and alloys. Swab specimen upto 20 seconds. |
HF |
6 ml |
|
2 ml |
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 upto a few minutes. |
Nitric acid |
1-10 ml |
Marbel’s Reagent |
CuSO4 |
10 grams |
Immerse or swab for 5-60 seconds |
For etching Ni, Ni-Cu and Ni-Fe alloys and superalloys. Add a few drops to H2SO4 to increase activity. |
HCl |
50 ml |
Water |
50 ml |
Murakami’s |
K3Fe(CN)6 |
10 grams |
Pre-mix KOH and water before adding K3Fe(CN)6 |
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°C; W and alloys use fresh and immerse; WC-Co and complex sintered carbides. |
KOH |
10 grams |
Water |
100 ml |
Picral |
Ethanol |
100 ml |
Seconds to minutes Do not let etchant crystallize or gry-expolisive |
Recommended for microstructures containing ferrite and carbides. |
Picric Acid |
2 – 4 grams |
Vilela’s Reagent |
Glycerol |
45 ml |
Seconds to minutes |
Good for ferrite- carbide structures (tempered martensite) in iron and steel. |
Nitric acid |
15 ml |
HCl |
30 ml |