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Etchant Composition Conc. Conditions Comments
ASTM No. 30 Ammonia
Hydrogen Peroxide (3%)
DI Water
62.5 ml
125 ml
62.5 ml
 

Mix Ammonia and water before adding peroxide. Must be used fresh. Swab 5-45 seconds

 

For etching copper, copper alloys and copper-silver alloys.
Adler Etchant  

Copper ammonium chloride
Hydrochloric acid
Ferric chloride, hydrated
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
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.
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.
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.

 

 

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.

 

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