Metallographic 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.

ETCHING SAFETY

Recommended Etchants

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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)