Metallographic Etchants
COMMON ETCHANTS
CAUTION:Safety is very important when etching. Be sure to wear the appropriate protective clothing and observe all WARNINGS on chemical manufacuters SDS (Safety Data Sheets). 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 |
|---|---|---|---|---|
| Adler Etchant | Copper ammonium chloride Hydrochloric acid FeCl3 DI Water |
9 grams 150 ml 45 grams 75 ml |
Immersion is recommended for several seconds | For etching 300 series stainless steel and Hastelloy superalloys |
| Ammonium Persulfate Etchant | Ammonium Persulfate DI Water |
50 grams 245 ml |
Immersion is recommended for several seconds | For brasses, especially brasses containing Cobalt (250 ml) |
| Aluminum Al-NaOH Etchant | Sodium Hydroxide DI Water |
25 grams 245 ml |
Immersion is recommended for several seconds | For etching aluminum and aluminum alloys |
| ASTM No. 30 | Ammonia H2O2 (3%) DI Water |
62.5 ml 125 ml 62.5 ml |
Immersion etching at 20 degrees Celsius | Copper etchant (250 ml) |
| ASTM No. 97 | KOH DI Water |
187.5 grams Total 250 ml |
Immersion etching at 20 degrees Celsius | Iron, Nickel, Chromium alloys (250 ml) |
| ASTM No. 157 | CrO3 Hydrochloric Acid DI Water |
31.25 grams 187.5 ml 62.5 ml |
Immersion etching at 20 degrees Celsius | Hastelloy Etchant (250 ml) |
| Berahas Etchant | Na2S2O3 K2S2O5 DI Water |
25 grams 7.5 grams 250 ml |
Immersion etching at 20 degrees Celsius | Tool steel etchant - Colors ferrite, martensite, bainite, and pearlite. Cementite unaffected (250 ml) |
| Carpenters Stainless Steel Etch | FeCl3 CuCl2 Hydrochloric acid Nitric acid Ethanol |
8.5 grams 2.4 grams 122 ml 6 ml 122 ml |
Immersion etching at 20 degrees Celsius | For etching duplex and 300 series stainless steels |
| Copper No. 1 | Nitric Acid Distilled Water |
125 ml 125 ml |
Immersion or swabbing etch at 20 degrees Celsius | Copper and Brass (nitric acid and DI water) (250 ml) |
| Copper No. 2 | Hydrochloric acid Ferric Chloride Distilled Water |
50 ml 10 grams 200 ml |
Immersion or swabbing etch at 20 degrees Celsius | Copper and Brass (HCl and ferric chloride) (250 ml) |
| Copper Sulfate Passivation | Hydrochloric acid Ferric Chloride Distilled Water |
50 ml 10 grams 200 ml |
Immersion or swabbing etch at 20 degrees Celsius | Copper and Brass (HCl and ferric chloride) (250 ml) |
| Dichromate Etchant | K2Cr2O7 Sulfuric acid Saturated NaCl Distilled Water |
8.9 grams 36 ml 18 ml 445 ml |
Immersion etch at 20 degrees Celsius | Detection of free iron on the surface of austenitic stainless steels (500 ml) |
| Frys Reagent | Hydrochloric acid Copper Chloride Distilled Water Alcohol |
100 ml 12.5 grams 75 ml 65 ml |
Immersion etch at 20 degrees Celsius | Martensitic 400 series stainless steels (250 ml) |
| Inconel Etchant | Nitric Acid Hydrochloric acid H2O2 (30%) Distilled Water |
50 ml 75 ml 35 ml 90 ml |
Immersion or swabbing etch at 20 degrees Celsius | For etching Inconel-type alloys on NiCr and Ni-Fe-Cr basis |
| Kalling's No. 2 | CuCl2 Hydrochloric acid Ethanol |
5 grams 100 ml 100 ml |
Immersion or swabbing etch at 20 degrees Celsius | For etching duplex and 400 series stainless steels and Ni-Cu alloys and superalloys. |
| Kellers Etch | Distilled water Nitric acid Hydrochloric acid Hydrofluoric acid |
190 ml 5 ml 3 ml 2 ml |
10-30 second immersion. Use only fresh etchant | Excellent for aluminum and titanium alloys. |
| Klemm's Reagent | Sodium thiosulfate solution Potassium metabisulfite |
250 ml Saturated 5 grams |
Etch for a few seconds to minutes | For etching alpha-beta brass, bonze, tin, cast iron phosphides, ferrite, martensite, retained austenite, zinc and steel temper embrittlement. |
| Klemm's 2 Reagent | Sodium thiosulfate solution Potassium metabisulfite |
250 ml Saturated 25 grams |
Etch for a few seconds to minutes at 40°C | Stain or tint etch for etching cast iron, copper and tin. |
| Kroll’s Reagent | Distilled water Nitric acid Hydrofluoric acid |
92 ml 6 ml 2 ml |
Swab specimen up to 20 seconds |
Excellent for titanium and alloys. |
| Nital | Ethanol Nitric acid |
100 ml 1-10 ml |
Immersion up to a few 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. |
| Marble's Reagent | CuSO4 Hydrochloric acid Water |
10 grams 50 ml 50 ml |
Immerse or swab for 5-60 seconds. | 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 KOH Water |
10 grams 10 grams 100 ml |
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 Celcius; W and alloys use fresh and immerse; WC-Co and complex sintered carbides. |
| Oberhoffers Reagent | FeCl3 SnCl2 Hydrochloric acid DI Water Ethanol |
7.2 grams 0.12 grams 10 ml 120 ml 120 ml |
Immersion or swabbing etch at 20 degrees Celsius | Steels and special steels, Fe-enriched areas appear dark (250 ml) |
| Picral | Ethanol Picric acid |
100 ml 2-4 grams |
Seconds to minutes Do not let etchant crystallize or dry –explosive |
Recommended for microstructures containing ferrite, carbide, pearlite, martensite and bainite. Also useful for magnetic alloys, cast iron, high alloy stainless steels and magnesium. |
| Ralphs Etchant | FeCl3 CuCl2 Hydrochloric acid D.I. Water Alcohol |
4.4 grams 1.25 grams 62.5 ml 62.5 ml 125 ml |
Immersion or swabbing etch at 20 degrees Celsius | Ferritic stainless steels (250 ml) |
| Schantz Etchant | FeCl3 Sulfuric acid Hydrochloric acid Nitric acid Acetic acid D.I. Water |
17 grams 10 ml 110 ml 30 ml 40 ml 55 ml |
Immersion or swabbing etch at 20 degrees Celsius | Nickel and cobalt alloys (250 ml) |
| Titanium Attack Polish | Colloidal Silica NH4OH H2O2 (30%) |
432 ml 43 ml 16 ml |
Used as a CMP polishing compound for titanium (500 ml) | |
| Vilella’s Reagent | Picric Acid Hydrochloric acid Ethanol |
1 gram 5 ml 100 ml |
Seconds to minutes | Good for ferrite-carbide structures (tempered martensite) in iron and steel |
| V2A Etchant |
Hydrochloric acid Nitric Acid Distilled Water |
119 ml 12 ml 119 ml |
Immersion or swabbing etch at 20 degrees Celsius | For etching austentic stainless steels |
| Waterless Kalling's | CuCl2 Hydrochloric acid Ethanol |
6.25 grams 125 ml 125 ml |
Immersion or swabbing etch at 20 degrees Celsius | For etching duplex and 400 series stainless steels and Ni-Cu alloys and superalloys. |
| Weck's Etchant | Ammonium Bifluoride
Hydrochloric acid Distilled water |
7.5 grams 10 ml 240 ml |
Immersion or swabbing etch at 20 degrees Celsius | Weck's tint etch for Ti and alloys. Alpha grains and twins colored according to orientation (250 ml) |
| Winsteard’s Reagent | Picric Acid Hydrochloric acid DI Water Surfactant Ethanol |
2 grams 5 drops 200 ml 5 ml 10 ml |
Immersion or swabbing etch at 20 degrees Celsius | Iron and nickel base alloys (250 ml) |
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