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 MSDS. Also review the COMMENTS and CONDITIONS Section for each etchant.

Recommended Etchants

Aluminum alloys		High carbon steel
Brasses and Bronzes		Stainless steel
Cast Iron		Tin alloys
Copper alloys		Zinc alloys
Low carbon steel		Ceramics

The following table lists the most commonly used etchants

Etchant	Composition	Conc.	Conditions	Comments
Kalling's No. 1	Distilled water CuCl2 Hydrochloric acid Ethanol	33 ml 1.5 grams 33 ml 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 Hydrochloric acid Ethanol	5 grams 100 ml 100 ml	Immersion etching at 20 degrees Celcius	For etching duplex 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 alloys - immersion for 10-20 seconds ; titanium alloys immersion for 10-20 seconds.
Kroll’s Reagent	Distilled water Nitric acid Hydrofluoric acid	92 ml 6 ml 2 ml	15 seconds	Excellent for titanium and alloys. Swab specimen up to 20 seconds.
Nital	Ethanol Nitric acid	100 ml 1-10 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 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.
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 and carbide.
Vilella’s Reagent	Glycerol Nitric acid Hydrochloric acid	45 ml 15 ml 30 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 (NH₄OH)	-	35%

Metallographic Etchants

Metallographic Etchants

Ordering on-line
Technical information
MSDS sheets

Brochures and catalogs

Metallography Support

COMMON ETCHANTS

Metallographic Etchants

Metallographic Etchants

Ordering on-line Technical information MSDS sheets

Brochures and catalogs

Metallography Support

COMMON ETCHANTS

Ordering on-line
Technical information
MSDS sheets