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Metallographic Etchants

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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
Aluminum alloys Brasses and Bronzes Cast Iron
Metallographic micrograph of aluminum Metallographic micrograph of Bronze Metallographic micrograph of cast iron
Ceramics Copper alloys Hastelloy and Nickel Superalloys
Metallographic micrograph of BeO Metallographic micrograph of copper Metallographic micrograph of low carbon steel
High carbon steel Stainless steel Tin alloys
Metallographic micrograph of high carbon steel Metallographic micrograph of stainless steel Metallographic micrograph of tin
Welding or Low carbon steels Zinc alloys
Metallographic micrograph of low carbon steel Metallographic micrograph of zinc
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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 & 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 & 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 & 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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