Metallographic Etch

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Metallographic Etch's Database File Material: Cast irons (Fe)

Type: Microetching Method: Chemical etching

Etchant (electrolyte): 50 ml cold-saturated (in distilled water) sodium thiosulfate solution and 1g potassiurn metabisulfite.

Procedure: Imersion at room temperature for 40-120 s.

Remarks: Color etching. Ferrite colored brown. Carbides, phosphides and nitrides remain white, nitrides remain white. Phosphorus rich areas outlined.

Reference: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 37.

Material: Cast irons (Fe) Type: Microetching Method: Chemical etching

Etchant (electrolyte): 3 g potassium metabisulfite, 1g sulfamic acid, 100 ml distilled water.

Procedure: Imersion at room temperature for 30-40 s.

Remarks: Color etching. Ferrite colored. Carbides, phosphides and nitrides remain white. Sulfides colored white. Phosphorus rich areas aoutlined.

Etchant (electrolyte): 3 g potassium metabisulfite and 10 g sodium thiosulfate, anhydrous, in 100 ml distilled water (use after 4 %-picral pre-etch).

Procedure: Pre-etch with 4 % picral, 1-2 min. Imersion at room temperature for 2 min (until surface turns bluish red).

Remarks: Color etching. Spectacular coloration of ferrite grains as a function of crystallographic orientation.

Etchant (electrolyte): 2 ml hydrochloric acid (35 %), 0.5 ml selenic acid and 100 ml ethyl alcohol (95 %).

Procedure: After polishing, immerse for 5-6 min. If pre-etching in 2 % nital, immersion time is shorter: 2-3 min at room temperature. Remarks: Color etching. Cementite colored red-bright. Ferrite remains bright. Phosphides and silicon colores blue-green.

Etchant (electrolyte): 1 g sodium molybdate in 100 ml distilled water; acidify to pH 2.5 to 3 with nitric acid (use after nital pre-etch).

Procedure: Pre-etch with 2 % nital. Immerse at room temperature for 30-45 s.

Remarks: Color etching. Phosphides and cementite colored yelow-orange. Sulfides remains light gray. Ferrite remains white.

Etchant (electrolyte): 1 g sodium molybdate and 100-500 mg ammonium bifluoride in 100 ml distilled water; acidify with nitric acid to

pH 2.5 to 3.5 (use after nital pre-etch).

Procedure: Pre-etch with 2 % nital. Immersion at room temperature for 30-45 s.

Remarks: Color etching. Phosphides and cementite colored blue-violet. Ferrite colored white-yellow.

Etchant (electrolyte): 100 ml reagent (240 g sodium thiosulfate, 24 g lead acetate and 30 g citric acid in 1000 ml distilled water (use after ammonium persulfate pre-etch)) plus 200 mg sodium nitrite.

Procedure: Pre-etch in 2 % nital. Immersion at room temperature until surface turns blue-violet.

Remarks: Color etching. Phosphides colored yellow-brown. Sulfides appear bright. All other phases colored blue--violet.

Etchant (electrolyte): 240 g sodium thiosulfate, 30 g citric acid and 20-25 g cadmium chloride in 1000 ml distilled water.

Procedure: Pre-etch in 2 % nital. Immersion at room temperature (after filtering sulfur particles) for 20-90 s.

Remarks: Color etching. After short immersion time (20-40 s), only ferrite is colored (red or violet). After longer immersion time, all phases are colored: phosphides, brown-orange; ferrite, yellow or light blue; cementite, red-violet or blue.

Material: Carbon steels, alloy steels, tool steels (Fe) Type: Microetching

Method: Chemical etching

Etchant (electrolyte): 1 g sodium metabisulfite; dilute to 100 ml with distilled water.

Procedure: Immersion at room temperature for 60-120 s.

Remarks: Color etching. Colors lath-type and plate-type martensite in Fe-C alloys.

Etchant (electrolyte): 30 g acetone sodium bisulfite; dilute to 100 ml with distilled water.

Procedure: Immersion at room temperature for up to 120 s. Remarks: Color etching. Colors the martensite in Fe-C alloys. Reference: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 47.

Etchant (electrolyte): 50 ml cold-saturated (in distilled water) sodium thiosulfate solution and 1g potassiurn metabisulfite.

Procedure: Irnmersion at room temperature for 40-120 s.

Remarks: Color etching. Colors pearlite and hardened structures of unlloyed steels. Ferrite colored brown-black (dark red-dark violet), carbides, phosphides and nitrides remain white.

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Etchant (electrolyte): 50 ml cold-saturated (distilled water) sodium thiosulfate solution and 5 g thiosulfate.

Procedure: Immersion at room temperature. Etching time depends on kind of steel.

Remarks: Color etching. For Mn, Mn-C, Mn-Cr steels. Epsilon martensite remains white; alpha martensite is colored black. Gama iron is colored gray.

Etchant (electrolyte): 3 g potassium metabisultite in 100 ml distilled water.

Procedure: Immersion at room temperature for 2-3 min. Remarks: Color etching. Colors ferrite grains. Reveals banded structures. Used in carbon and alloy steels.

Etchant (electrolyte): 3 g potassium metabisulfite, 1g sulfamic acid, 100 ml distilled water.

Procedure: Immersion at room temperature for 30-120 s. Remarks: Color etching. For carbon, alloy and manganese steels. Colors ferrite grains. Carbides and phosphides remain white.

Etchant (electrolyte): 3 g potassium metabisulfite and 10 g sodium thiosulfate, anhydrous, in 100 ml distilled water (use after 4 %-picral pre-etch).

Procedure: Pre-etch with 4 % picral for 1-2 min. Immersion at room temperature for 2 min.

Remarks: Color etching. For carbon, alloy and Fe-Mn (5-18 % Mn) steels.

Reveals Chemical and physical heterogeneity, ferrite grains, carbides, nitrides, phosphides remain white. Immerse 4-5 min for "line" etching. Reference: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 47.

Etchant (electrolyte): Stock solution: 1:5 v/v hydrochloric acid (35 %) and distilled water, 100 ml of the stock solution plus 0.5-1 g potassium metabisulfite.

Procedure: 100 cc etchants + 2 g ammonium bifluoride + 1 g potassium metabisulfite. Immersion at room temperature for 5-8 s. Remarks: Color etching. For carbon, alloy and tool steels. Martensite is colored blue. Bainite is colored red.

Etchant (electrolyte): 2 ml hydrochloric acid (35 %), 0.5 ml selenic acid and 100 ml ethyl alcohol (95 %).

Procedure: After polishing, immersion at room temperature for 5-6

min. After nital pre-etching, immerse for shorter time 2-3 min. Remarks: Color etching. For carbon and tool steels. Carbides colored red to blue. Colors nitrided zone in nitriding steels. Ferrite remains bright.

Etchant (electrolyte): 1 g sodium molybdate and 100-500 mg ammonium bifluoride in 100 ml distilled water; acidify with nitric acid to pH 2.5 to 3.5 (use after nital pre-etch).

Procedure: Pre-etch in nital. Immersion at room temperature for 30-60 s.

Remarks: Color etching. For carbon and alloy, steels and some tool steels. Carbides colored brown-violet. Ferrite colored white-yellow, depending on the amount of ammonium bifluoride.

Etchant (electrolyte): 100 ml reagent (240 g sodium thiosulfate, 24 g lead acetate and 30 g citric acid in 1000 ml distilled water (use after ammonium persulfate pre-etch)) plus 200 mg sodium nitrite.

Procedure: Pre-etch in 2 % nital. Immersion at room temperature until specimen surface turns blue-violet.

Remarks: Color etching. For carbon and alloy steels and some tool steels. Sulfides in free-cutting steels colored white. All other phases colored blue-violet.

Etchant (electrolyte): 240 g sodium thiosulfate, 30 g citric acid and 20-25 g cadmium chloride in 1000 ml distilled water.

Procedure: Pre-etch in 2 % nital. Immersion at room temperature (after filtering sulfur particles) for 20-90 s.

Remarks: Color etching. For carbon and alloy steels. Sulfides remain bright. Other phases colored: ferrite, yellow or light blue; carbides, red-violet-blue.

Material: Stainless steels (Fe) Type: Microetching

Etchant (electrolyte): For step 1 (pre-etching): 25 ml nitric acid and 75 ml ethyl alcohol (95 %), for step 2: 15 to 35 g sodium metabisulfite; dilute to 100 ml with distilled water.

Procedure: Step 1: Pre-etch with 25 ml HNO3 + 75 ml ethyl alcohol by immersion for approx 10 s. (Caution: HNO3 and ethyl alcohol are dangerous at this concentration.) Step 2: Etch with 15 to 35 g sodium metabisulfite diluted to 100 ml with distilled water. Immersion at room temperature for 2 min or until polished surface turns bluish red. Remarks: Color etching. Tint etchant for Fe-Ni alloys from 5-25 % Ni. Colors martensite packets of different orientations to different colors. Reveals the substructure of lath-type martensite.

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and 0.5-1 g ammoniurn bifluoride in 100 ml distilled water. Procedure: Immersion at room temperature until coloration is obtained.

Remarks: Color etching. Etching of ferritic and martensitic stainless steel. General color etching for microstructure of ferritic and martensitic stainless steels. Reveals delta ferrite.

Etchant (electrolyte): Stock solution: 1:5 v/v hydrochloric acis (35 %) and distilled water, 100 ml of the stock or stock solution: 1:2 or 1:1 or 1:0.5 v/v hydrochloric acid (35 %) and distilled water. 100 ml of stock solution plus 0.6-1 g potassium metabisuifite. Optional addition of 1 -3 g ferric chloride or 1 g cupric chloride or 2-10 g ammonium bifluoride solution plus 0.5-1 g potassium metabisulfite.

Procedure: Immersion at room temperature for 30-120 s. Keep specimen moving during etching. When good coloration is not produced and when etching heat-resisting steels, use reagent (stock solution: 1:2 or 1:1 or 1:0.5 v/v hydrochloric acid (35 %) and distilled water, 100 ml of stock solution plus 0.6-1 g potassium metabisulfite. Optional addtions of 1-3 g ferric chloride or 1 g cupric chloride or 2-10 g ammonium bifluoride) (1:1 or 1:0.5) and a longer etching time. Remarks: Color etching. Etching of austenitic stainless steels. Colors the austenitic matrix, leaving carbides and nitrides white (uncolored). Reference: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 62.

Etchant (electrolyte): Stock solution: 1:5 v/v hydrochloric acis (35 %) and distilled water, 100 ml of the stock.

Procedure: 100 cc of etchant (electrolyte) + 2 g ammonium bifluoride + 1 g potassium metabisulfite. Immersion at room temperature (22 + 5 C) for 5-8 s.

Remarks: Color etching. Etching of martensitic stainless steel. Colors martensite blue in martensitic and austenitic stainless steel.

Etchant (electrolyte): 5-10 ml hydrochloric acid (35 %), 1- 3 ml selenic acid and and 100 ml ethyl alcohol (95 %).

Procedure: Immersion at room temperature until coloration is obtained.

Remarks: Color etching. Color etching of ferritic, austenitic and martensitic stainless steels.

Etchant (electrolyte): 20-30 ml hydrochloric acid (35 %), 1-3 ml selenic acid and 100 ml ethyl alcohol (95 %).

Procedure: Clean and wet specimen. Immerse at room temperature for 1-4 min.

Remarks: Color etching. Etching of stainless steels. Colors carbides and gamma- prime phase in and heat-resisting steels.

Etchant (electrolyte): 20 g ammonium bifluoride and 0.5 g potassium metabisulfite in 100 ml distilled water.

Procedure: Immersion at room temperature. Etching time is 1-2 min. Remarks: Color etching. Etching of austenitic stainless steels and welds. Reveals delta ferrite in welds.

Material: Heat-resisting steels and alloys (Fe) Type: Microetching

Etchant (electrolyte): Stock solution: 1:2 or 1:1 or 1:0.5 v/v hydrochloric acid (35 %) and distilled water. 100 ml of stock solution plus 0.6-1 g potassium metabisuifite. Optional addition of 1-3 g ferric chloride or 1 g cupric chloride or 2-10 g ammonium bifluoride. Procedure: Immersion at room temperature for 60-150 s. Keep specimen moving during etching. When good coloration is not produced, use 1:1 or 1:0.5, and a longer etching time.

Remarks: Color etching. Etching of Fe-Ni and Co-base heat-resisting alloys. Colors the matrix. Leaves carbides and nitrides white (uncolored).

Etchant (electrolyte): Stock solution: 1:2 or 1:1 or 1:0.5 v/v hydrochloric acid (35 %) and distilled water. 100 ml of stock solution plus 0.6-1 g potassium metabisuifite. Optional addition of 1 -3 g ferric chloride or 1 g cupric chloride or 2-10 g ammonium bifluoride. Procedure: (1:1 + addition to 500 ml of 1-1.5 g ferric chloride). Immersion at room temperature for 60-150 s. Keep specimen moving during etching. When good coloration is not produced, use longer etching time.

Remarks: Color etching. Etching of Fe, Ni and Co base heat resisting alloys. Colors the matrix. Leaves carbidcs and nitrides white

(uncolored).

Etchant (electrolyte): Stock solution: 1:2 or 1:1 or 1:0.5 v/v hydrochloric acid (35 %) and distilled water. 100 ml of stock solution plus 0.6-1 g potassium metabisuifite. Optional addition of 1-3 g ferric chloride or 1 g cupric chloride or 2-10 g ammonium bifluoride. Procedure: (1:1 + addition of 100 ml of 2-10 g ammonium bifluoride). lmmersion at roorn temperature for 60-150 s. Keep specimen moving during etching. When good coloration is not produced, use a longer etching time.

Remarks: Color etching. Etching of Fe, Ni and Co base heat resisting alloys. Colors the matrix. Leaves carbidcs and nitrides white

(uncolored).

Etchant (electrolyte): 20-30 ml hydrochloric acid (35 %), 1-3 ml selenic acid and 100 ml ethyl alcohol (95 %).

Procedure: Clean and wet specimen. Immerse at room temperature for 1-4 min.

Remarks: Color etching. Etching of Fe, Ni and Co base heat-resisting alloys. Colors carbides and phase. Leaves the rnatrix white

(uncolored).

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Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 74.

Material: Aluminum alloys (Al) Type: Microetching

Etchant (electrolyte): 2-3 g sodium molybdate, 5 ml hydrochloric acid (35 %) and 1-2 g ammonium bifluoride in 100 ml destilled water. Procedure: Immersion at room temperature until color is obtained (depends on specimen's chemical compostion).

Remarks: Color etching. Slightly colors the CuAl2 phase. Al-Cu-Fe-Mn script colored blue; FeSiAl3 phase colored brown-blue; NiAl, or phase FeNiAl9 colored brown; aluminum matrix remains bright (uncolored). Reference: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 87.

Etchant (electrolyte): 200 g chromic acid, 20 g sodium sulfate, and 17 ml hydrochloric acid (35 %) in 1000 ml distilled water.

Procedure: Pre-etch:10 % NaOH followed by 50 % HNO3 in H2O. Rinse in water and immediately dip in etchant (electrolyte) for 1-5 s. Rinse and dry.

Remarks: Color etching. Coloring of the matrix grains, improves contrast and clearly outlines inclusions and insoluble particles. Reference: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 87.

Procedure: Immersion at room temperature for 5-30 s. Remarks: Color etching. Detects the susceptibility of wrought aluminum alloys to intergranular corrosion by black coloring of grain boundaries.

Etchant (electrolyte): 0.5 ml hydrofluoric acid plus 100 rnl distilled water.

Procedure: Immersion at room temperature. Time required for color metallography is longer than for usual etching (15-60 s).

Remarks: Color etching. In cast aluminum alloys having a high Ni and Fe content, strong coloration occurs: pure iron is colored green, pure nickel is colored gray-brown, FeNiAl9 intermetallic compound is colored blue-violet. The aluminum matrix remains uncolored.

Etchant (electrolyte): Acid mixture of 0.5 % hydrofluoric acid plus 1.5 % hydrochloric acid and 2.5 % nitric acid in aqueous solution. Procedure: Immersion at room temperature. Etching time approx 5-25 s.

Remarks: Color etching. Etching of cast aluminum alloys. Colors nickel-rich phases brown and heavily darkens the !vIg2Si phase. The aluminum matrix and silicon remain uncolorcd.

Etchant (electrolyte): 20 % sulfuric acid in aqueous solution. Procedure: Immersion for approx 30 s at 70 C (150 F).

Remarks: Color etching. Etching of cast aluminum alloys. Colors AI-Cu-Fe-Mn rich phases brown. Darkens the Mg2Si phase, outlines other phases, leaves the aluminum matrix uncolored.

Etchant (electrolyte): 10 % sodium hydroxide in aqueous solution. Procedure: Immersion for approx. 5 s at 70 C (150 F).

Remarks: Color etching. Etching of cast aluminum alloys. Colors CuAl2 and MglSi phases brown, outlines AI-Cu- Fe-Mn phase. Reference: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 87.

Material: Copper alloys (Cu) Type: Microetching

Etchant (electrolyte): 2 ml hydrochloric acid (35 %), 0.5 ml selenic acid and 300 ml ethyl alcohol (80-85 %) (use after ammonium persulfate pre-etch).

Procedure: Pre-etch in (A) 10 % amononium persulfate solution or (B) with ammonium persulfate/ammonia solution. Immerse at 24 ± 3 C (75.2 ± 37.4 F) and watch color change of specimen surface (yellow, orange, red, violet, blue and finally silvery bright). Etching should be interrupted when the surface turns violet-blue or blue. Reaching silvery bright color should be avoided.

Remarks: Color etching. Colors differently grains and twins in monophase alloys, leaves beta phase bright and contrasting with the colored alpha phase in alpha-beta brass. Iron or iron-rich phases remain bright, gamma phasc (CuBe) in beryllium copper is colored differently from alpha phase. In more complex brasses or bronzes, differential coloration enables the identification of different phases. Reference: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 96.

Etchant (electrolyte): 240 g sodium thiosulfate, 24 g lead acetate and 30 g citric acid in 1000 ml distilled water (use after ammonium persulfate pre-etch).

Procedure: Pre-etch in 10 % ammonium persulfate solution. Immerse at room temperature (24 ± 3 C) (75.2 ± 37.4 F) and watch color changes of specimen surface (red, violet, blue, silvery bright consutively). Copper and monophase alloys should be removed from the solution when the surface turns red or violet. Polyphase alloys must be removed before reaching silvery bright color.

Remarks: Color etching. In copper or monophase alloys, the matrix grains and twins (and sometimes inclusions and undissolved particles also) are differently colored. Polyphase alloys usually show violet, blue or green alpha phase, red, yellow, green or blue beta phase and white iron and iron rich particles. The gamma phase (CuBe) in beryllium-copper alloys will appear bright against the blue or violet matrix. Reference: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 96.

Procedure: Immersion at room temperature. Agitate slowly for 2-20 s. Rinse in water and dry. If necessary, repeat. Total etching time should

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be 1-5 min.

Remarks: Color etching. Differently colors matrix grains and twins, and greatly enhances Chemical contrast. Constituents and inclusions may or may not be colored.

Material: Titanium alloys (Ti) Type: Microetching

Etchant (electrolyte): 2-3 g sodium molybdate, 5 ml hydrochloric acid (35 %) and 1-2 g ammonium bifluoride in 100 ml destilled water. Procedure: Immersion at room temperature until specimen surface occurs.

Remarks: Color etching. Etching of as-cast titanium alloys.Titanium alpha matrix is colored blue or green. TiC is colored yellow or dark brown.

Etchant (electrolyte): 5 g ammonium bifluoride in 100 ml distilled water.

Procedure: For pure titanium, immersion at room temperature for a few sonds. Longer etching time required for titanium alloys. Remarks: Color etching. Titanium alpha grains and twins are differently colored according to their crystallographic orientation. sondary phases are evident by coloring.

Etchant (electrolyte): 3 g ammonium bifluoridie and 4 ml hydrochloric acid (25 %) in 100 ml distilled water.

Procedure: Immersion at room temperature for a few sonds. (To obtain good coloring, last polishing stage should be carried out in, or with, saturated solution of oxalic acid.).

Remarks: Color etching. Alpha titanium grains are differently colored. sondary alpha and alpha-prime and various intermetallic phases (such as Ti2Cu) remain white (uncolored) or are evident by coloring. Reference: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 111.

Method: Physical etching Etchnant: Thermal etching

Procedure: The specimen is polished and tinting removed from bakelite holder. Heating is done in a stainless steel or tungsten-filament basket in air. Basket temperature 1200 C (2192 F) approx. Specimen temperature approx. 400-600 C (752-1112 F). Time approx. 15-60 s. Air blowing improves both oxidation rate and time and specimen's temperature control.

Remarks: Color etching. Different coloring of the matrix and the various phases is obtained. In titanium-aluminides-based alloys, the TiAl matrix usually appears yellow and brown. The Ti3Al phase usually appears blue or green.

Material: Uranium alloys (U) Type: Microetching

Method: Electrolytic etching

Etchant (electrolyte): 420 cc glacial acetic acid, 50 g chromic acid, 60 cc water.

Procedure: Cathode: stainless steel, current density: 0.6-0.8 A/cm2, voltage: 35 V, time: 80 s, temperature: 20-25 C (68-77 F).

Remarks: Color etching. Electrolytic polishing with electrolyte. Reference: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 112.

Material: Uranium alloys (U) Type: Microetching

Etchant (electrolyte): 420 cc glacial acetic acid, 50 g chromic acid, 60 cc water.

Procedure: Cathode: stainless steel, current density: 0.2-0.5 A/cm2, voltage: 35 V, time: 10-15 s, temperature: 20-25 C (68-77 F). Remarks: Color etching. Electrolytic etching.

Material: Uranium alloys (U) Type: Micro etching

Method: Physical etching

Etchant (electrolyte): Oxidation in air.

Procedure: Temperature 100-200 C (212-392 F). Remarks: Color etching for uranium alloys.

Material: Silver (Ag) Type: Macroetching Method: Chemical etching

Etchant (electrolyte): 95 ml methanol (95 %), 10 ml nitric acid. Procedure: Several minutes.

Remarks: Pure Ag and low alloy Ag, grain contrast.

Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 37.

Material: Silver (Ag) Type: Microetching Method: Chemical etching

Etchant (electrolyte): 100 ml distilled water, 2-11 ml sulfuric acid, 2 g chromium (VI) oxide (concentration variable).

Procedure: Up to 1 min.

Remarks: Predominantly used for Ag alloys, especially Ag-Ni alloys and Ag-Mg-Ni alloys.

Etchant (electrolyte): 10 ml sulfuric acid, 100 ml saturated aqueous solution of potassium dichromate, 2 ml saturated aqueous solution of sodium chloride.

Procedure: Seconds to minutes, 1:9 dilution with distilled water. Possibly without sulfuric acid.

Remarks: Pure Ag and Ag alloys, Ag solders.

Material:Silver (Ag) Type: Microetching Method: Chemical etching

Etchant (electrolyte): A: 100 ml distilled water, 10 g amonium persulfate, B: 100 ml dest. water, 10 g potassium cyanide.

Procedure: 30 s to 2 min. Mix (A) and (B) before etching in proportion 1:1.

Remarks: Ag and low alloy Ag.

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Etchant (electrolyte): 100 ml amonia water, 5-10 g potassium cyanide.

Procedure: Several seconds.

Remarks: Pure Ag and Ag composites with other metals. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 39.

Etchant (electrolyte): 50 ml amonia water, 50 ml hydrogen peroxide (3 %).

Procedure: Up to 11 min. Use fresh!

Remarks: Pure Ag, Ag-Ni alloys, Ag-Pd alloys.

Etchant (electrolyte): 25 ml distilled water, 50 ml hydrogen peroxide (3 %), 25 ml amonia water.

Procedure: Up to 1 min. Use fresh!.

Remarks: Ag rich Ag-Cd alloys, Ag solders, Ag-Cu alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 39.

Etchant (electrolyte): 100 ml distilled water, 2 g iron (III) chloride. Procedure: 5-30 s.

Remarks: Ag solders.

Etchant (electrolyte): 10 ml aqueous solution of sodium (10 %), 10 ml acqueous solution of potassium ferrocyanide (30%).

Procedure: 5-15 s. If attack too rapid dilute 50 % with. distilled water. Remarks: Ag-Mo alloys, Ag-W alloys, Ag-W carbides.

Material: Silver (Ag) Type: Microetching Method: Electrolytic etching

Etchant (electrolyte): 10 ml distilled water, 10 g citric acid.

Procedure: 6 V dc, Ag cathode. Possibly drops 2-3 drops nitric acid, time 15 s to 1 min.

Remarks: Ag alloys.

Material: Aluminium (Al) Type: Macroetching Method: Chemical etching

Etchant (electrolyte): 100 ml distilled water, 10-20 g sodium hydroxide.

Procedure: 5-15 min, 60-70 C (140-160 F). More concentrated solutions work also at room temperature.

Remarks: Suitable for most types of Al and Al alloys.

Etchant (electrolyte): 75 ml hydrochloric acid , 25 ml nitric acid, 5 ml hydrofluoric acid (40 %).

Procedure: Few seconds to minutes. Use fresh!. Possibly diluted with 25 ml distilled water. Rinse in warm water.

Remarks: Al alloys containing Cu, Mn, Si and Ti. Al cast alloys with high Si content.

Material: Aluminium (Al) Type: Macroetching Method: Microetching

Etchant (electrolyte): 90 ml distilled water, 15 ml hydrochloric acid, 10 ml hydrofluoric acid (40 %)(Flick's reagent).

Procedure: 5 s to 3 min.

Remarks: Al base materials in general. Pure Al, Cu-Al alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 40.

Etchant (electrolyte): 20 (50) ml distilled water, 20 (15) ml

hydrochloric acid, 20 (25) ml ntric acid, 5 (10) ml hydrofluoric acid (40 %) (concentration variable).

Procedure: 1-3 min.

Remarks: Al base matrials in general. Hig purity Al. Alloys of Mn, Al-Mg, Al-Mg-Mn and Al-Mg-Si. Grain size. Rolling direction. Welded joints. Also useful for microetching.

Etchant (electrolyte): 25 ml distilled water, 45 ml hydrochloric acid, 15 ml nitric acid, 15 ml hydrofluoric acid (40%).

Procedure: Few seconds to minute. Use fresh!

Remarks: High purity Al, Mn-Al, Si-Al, Mg-Al and Mg-Si-Al alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 40.

Etchant (electrolyte): 100 ml distilled water, 5.5 ml sulfuric acid. Procedure: Few seconds to minute.

Remarks: Surface imperfections of pure Al.

Material: Aluminium (Al) Type: Microetching Method: Chemical etching

Etchant (electrolyte): 100 ml distilled water, 0.5 ml hydrofluoric acid (40 %). If necessary, increase of hydrofluoric acid to 10 ml.

Procedure: 10-60 s, minutes to 1 h. Alternative polishing and etching. Remarks: For most types of Al and Al alloys. Grain boundaries, slip lines in high purity Al.

Etchant (electrolyte): 190 (190) ml distilled water, 5 (10) ml nitric acid, 3 (6) ml hydrochloric acid, 2 (4) ml hydrofluoric acid (40 %).

Procedure: 10-30 s. Use only fresh!.

Remarks: For most types of Al and Al alloys. Exception: Al alloys with high Si content.

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Etchant (electrolyte): 100 ml distilled water, 1-2 g sodium hydroxide. Procedure: A: 5-10 s, possibly at 50 C (120 F). Use only fresh!. Rinse in mixture: 95 ml distilled water, 5 ml ntric acid, B: Etch 15 min, rinse in water approx. 10 min.

Remarks: Pure Al, Allloys of Cy-Al, Mg-Si-Al, Mg-Al, and Zn-Al. If etching times are short, Al2Cu is not colored. For shrink etching. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 42.

Etchant (electrolyte): 100 ml distilled water, 0.5-25 g sodium hydroxide, 1g zinc chloride.

Procedure: Few seconds to minutes. Remarks: For most types of Al and Al alloys.

Etchant (electrolyte): 75 ml distilled water, 25 ml nitric acid. Procedure: 40 s, 70 C (160 F).

Remarks: For most of AL and Al alloys, especially those containing Cu.

Etchant (electrolyte): 92 ml distilled water, 6 ml nitric acid, 2 ml hydrofluoric acid (40 %).

Procedure: 15 s.

Remarks: Especially for Cu-Al alliys (also useful in macroetching). Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 42.

Etchant (electrolyte): 80 ml distilled water, 20 ml sulfuric acid. Procedure: 30 s to 3 min, 70 C (160 F).

Remarks: Differentiantion of intermediate phases in Al with high contents of Cu, Mn, Mg, Fe, Be, Ti, Fe3Al.

Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 42

Etchant (electrolyte): 100 ml distilled water, 9 g phosphoric acid (crystal).

Procedure: 30 min.

Remarks: Detection of susceptibility to intercrystaline corrosion of Al-Mg alloys. Distinct grain boundaries in corrosion sensitive alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 42.

Etchant (electrolyte): 100 ml distilled water, 9 g phosphoric acid (crystal).

Procedure: Anneal sample to 100 C (212 F) and slow cool before etching.

Remarks: Precipitates of beta Al8Mg5 or Mg2, respectively. Shows strain in Al-Mg base alloys.

Etchant (electrolyte): 25 (50) ml methanol (95%), 25 (30) ml nitric acid, 25 (20) ml hydrofluoric acid (40 %).

Procedure: 10-60 s.

Remarks: Pure Al, Al-Mg and Al-Mg-Si alloys. Etch figures. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 42.

Etchant (electrolyte): 60 ml distilled water, 10 g sodium hydroxide, 5 g potassium ferricyanide.

Procedure: 2 min.

Remarks: Precipitates, grain boundaries, Al-Si and Al-Cu alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 42.

Material: Aluminium (Al) Type: Microetching Method: Electro etching

Etchant (electrolyte): 90 ml distilled water, 10 ml phosphoric acid. Procedure: A: 1-3 min, 50 C (120 F), B: Electrolytic, 5-10 s, 1-8 V dc, stainless steel cathode.

Remarks: Pure Al, Al-Cu, Al-Mn, Al-Mg, Al-Mg-Si alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 43.

Material: Aluminium (Al) Type: Microetching Method: Electro etching

Etchant (electrolyte): 200 ml distilled water, 10 ml fluoboric acid (35 %).

Procedure: 1-2 min, 20-40 V dc. Do not wipe during rinsing. Cathode and anode fixtures should be made of high purity Al, Pb, or stainless steel.

Remarks: Pure Al, Al-Zn, Al-Mn, Al-Mg-Si, Al-Zn-Mg, Al-Mn-Mg alloys. View in polarized light.

Material: Gold (Au), platinum (Pt), palladium (Pd) Type: Macroetching

Etchant (electrolyte): 66 ml hydrochloric acid, 34 ml nitric acid. Procedure: Few minutes. Use hot and fresh!.

Remarks: Au, Pt alloys and Pd alloys.

Material: Ruthenium (Ru), osmium (Os), rhodium (Rh) Type: Macroetching

Etchant (electrolyte): 50 ml lactic acid (90 %) or hydrochloric acid, 20 ml nitric acid, 30 ml hydrofluoric acid (40 %).

Procedure: Few minutes.

Remarks: Ru and Ru alloys, Os and Os alloys, Rh and Rh alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p.43.

Material: Platinum (Pt) Type: Macroetching Method: Electro etching

Etchant (electrolyte): 80 ml saturated aqueous solution of sodium chloride, 20 ml hydrochloric acid.

Procedure: Few minutes. 6 V dc, Pt cathode. Remarks: Pt and Pt alloys.

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Material: Pure gold (Au), palladium (Pd) and rhodium (Rh) Type: Microetching

Etchant (electrolyte): 40 (1) ml nitric acid, 60 (10) ml hydrochloric acid.

Procedure: Few seconds to 1 min. May require heating. Use only fresh!.

Remarks: Pure Au and Pd. Au-Pd, Pd alloys with more than 90 % concentration of precious metals. Rh alloys.

Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p.44.

Material: Palladium (Pd), gold (Au) and platinum (Pt) Type: Microetching

Etchant (electrolyte): 100 ml distilled water, 10 g potassium cyanide. Procedure: 30 s to 2 min.

Remarks: Au alloys with less thn 90 % content of precious metals. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 45.

Material: Palladium (Pd), gold (Au) and platinum (Pt) Type:: Microetching

Etchant (electrolyte): 100 ml distilled water, 10 g ammonium persulfate.

Procedure: 30 s to 2 min.

Remarks: For Au alloys with high content of precious metals. White gold. Pd and Pt alloys.

Reference: G.Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 45.

Material: Au-Cu-Ag alloys (Au) Type: Microetching

Etchant (electrolyte): 100 ml distilled water, 100 ml hydrogen peroxide (3 %), iron (III) chloride.

Procedure: Few seconds to minutes. Remarks: For Au-Cu-Ag alloys.

Material: Gold (Au), palladium (Pd), platinum (Pt) Type: Microetching

Etchant (electrolyte): 30 (50) ml distilled water, 25 (100) ml hydrochloric acid, 5 (10) ml nitric acid.

Procedure: 1-5 min. Use hot.!. Remove precipitate of gold chloride with ammonia water.

Remarks: Pure Pt and Pd. Au alloys. Proportions in parentheses especially useful for Pt.

Material: Gold (Au), palladium (Pd), platinum (Pt) Type: Microetching

Etchant (electrolyte): 100 ml hydrochloric acid, 1-5 g chromium (VI) oxide.

Procedure: Seconds to minutes.

Remarks: Pure Au and Au-rich alloys. Pd and Pd alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 45.

Material: Osmium (Os) Type: Microetching Method: Chemical etching

Etchant (electrolyte): 150 ml distilled water, 3.5 g potassium ferricyanide, 1g sodium hydroxide.

Remarks: Os and Os-W alloys.

Material: Ruthenium (Ru) Type: Microetching Method: Chemical etching

Etchant (electrolyte): 80 ml distilled water, 20 ml hydrochloric acid, 1 ml hydrogen peroxide (3 %).

Remarks: Ru rich alloys and Ru-Mo alloys.

Material: Platinum (Pt), gold (Au) Type: Microetching

Etchant (electrolyte): 100 ml distilled water, 5 g potassium cyanide. Procedure: 1- 2 min, 1-5 V ac, 0.5-1.5 A/cm2, Pt cathode.

Remarks: Pt and Pt alloys, Au and Au alloys.

Material: Rhodium (Rh), platinum (Pt), iridium (Ir) Type: Microetching

Etchant (electrolyte): 65 ml distilled water, 20 ml hydrochloric acid, 25 g sodium chloride.

Procedure: 25 s, 10 V ac, 1 min, 1.5 V ac, 1-2 min, 20 V ac, 1 min, 6 V ac, 1 min, 5-20 V ac, graphite or Pt cathode.

Remarks: Rh bse alloys, Pt-10% Rh alloys, Ir alloys, pure Pt and Pt alloys, Ru base alloys.

Material: Osmium (Os), palladium (Pd), iridium (Ir) Type: Microetching

Etchant (electrolyte): 90 ml ethanol (96 %), 10 ml hydrochloric acid. Procedure: 90 s, 10 V dc., graphite cathode.

Remarks: Os base alloys, pure Pd and Pd alloys, Pt-Au alloys, Ir. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 45.

Material: Iridium (Ir) Type: Microetching Method: Electrolytic etching

Etchant (electrolyte): 90 ml distilled water, 5-10 ml hydrochloric acid. Procedure: 30 min to 3 h, 0.1 A/cm2, graphite or Pt cathode. Remarks: Iridium

Material: Platium (Pt), rhodium (Rh), iridium (Ir) Type: Microetching

Etchant (electrolyte): 80 ml distilled water, 20 ml sulfuric acid. Procedure: Up to 1h. 1-5 V ac, 0.05-0.2 A/cm2, graphite cathode. Remarks: Pt alloys, Rh, Ir.

Material: Beryllium (Be) Type: Macroetching Method: Chemical etching

Etchant (electrolyte): 90 ml distilled water, 10 ml hydrochloric acid, 4 g ammonium chloride.

Procedure: Few minutes. Immerse or swab.

Remarks: Technical types of Be. Especiallt with large grain size. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 46.

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Etchant (electrolyte): 90 ml distilled water, 10 ml hydrochloric acid, 2 g ammonium chloride, 2 g picric acid.

Procedure: Few minutes. Immerse or swab.

Remarks: Technical types of Be. Especially with large grain size. Low alloy Be.

Etchant (electrolyte): 25 ml sulfuric acid, 500 ml phosphoric acid, 59 g chromium (VI) oxide (possibly some distilled. water).

Procedure: Few seconds to minutes, 45 C (110 F), toxic. Remarks: Grain boundary etch.

Material: Beryllium (Be) Type: Microetching Method: Chemical etching

Etchant (electrolyte): 100 ml distilled water or ethanol (96 %), 2-10 ml hydrofluoric acid (40 %).

Procedure: Few seconds to minutes. Toxic. Remarks: Be alloys.

Etchant (electrolyte): 100 ml distilled water, 5 ml sulfuric acid. Procedure: 1-15 s.

Remarks: For most types of Be and Be alloys.

Etchant (electrolyte): 50 ml distilled water, 20 ml ammonia water, 3 ml hydrogen peroxide (30 %).

Procedure: Few seconds to minutes. Use only fresh. Remarks: Be-Ag and Be-Al-Ti alloys.

Etchant (electrolyte): 25 ml glycerol, 5 ml hydrofluoric acid (40 %), 3 ml nitric acid.

Procedure: Approx. 155 s. HF content may be raised to 15 ml. Toxic. Remarks: Be and Be alloys.

Etchant (electrolyte): 50 ml lactic acid (90 %), 50 ml nitric acid, 50 ml hydrochloric acid (40 %).

Procedure: Few seconds to minutes. Toxic. Remarks: Be-U, Be-Nb, Be-Y and Be-Zr alloys.

Etchant (electrolyte): 100 ml distilled water, 10 g oxalic acid. Procedure: 2 min. 16 min. Boiling.

Remarks: Precipitates, grain boundary.

Etchant (electrolyte): Saturated solution of copper (II) sulfate in distilled water.

Procedure: 30 s. Remarks: Precipitates.

Material: Beryllium (Be) Type: Microetching Method: Electrolytic etching

Etchant (electrolyte): 35 ml ethanol (96 %), 10 ml perchloric acid (10 %), 10 ml butyl glycol.

Procedure: 30-45 s, below 35 C (95 F), 50 V dc, stainless steel cathode.

Remarks: Be and Be alloys. Rapid attack. Toxic.

Etchant (electrolyte): 294 ml ehylene glycol, 4 ml hydrochloric acid, 2 ml nitric acid.

Procedure: 6 min, 30 C (85 F), 13-20 V dc, srainless steel cathode. Remarks: Be and Be alloys.

Etchant (electrolyte): 100 ml phosphoric acid, 30 ml glycerol, 30 ml ethanol (96 %), 2.5 ml sulfuric acid.

Procedure: 1 min, cool (10 C, 50 F), 25 V dc, stainless steel or Mo cathode.

Remarks: Be, grain boundary etch. Also used to increrase contrast in polarized light.

Material: Bismuth (Bi), antimony (Sb) Type: Macroetching

Etchant (electrolyte): A: 160 ml distilled water, 40 ml nitric acid, 30 ml glacial acetic acid, B: 400 ml distilled water, 1 ml galcial acetic acid. Procedure: First with A at 40 C (100 F). Repolish until surface has become bright. Repeat etching with B, 1-2 h.

Remarks: Sb-Pb, Bi-Sn alloys.

Etchant (electrolyte): A: 220 ml distilled water, 80 ml nitric acid, B: 300 ml distilled water, 45 g ammonium molybdate.

Procedure: Few seconds to minutes. Equal amounts of A and B are mixed before use.

Remarks: Technically pure Sb. Crystal arrangement. Sb-Bi alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 49.

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Etchant (electrolyte): 100 ml distilled water, 25 g citric acid, 10 g ammonium molybdate.

Procedure: Few seconds to minutes.

Remarks: Crystal arrangement. Casting imperfection in Sb and Bi. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 49.

Material: Bismuth (Bi), antimony (Sb) Type: Microetching

Etchant (electrolyte): 70 ml distilled water, 30 ml hydrochloric acid, 5 ml hydrogen peroxide (30 %).

Remarks: For pure and technically pure types of Sb. Low alloy Sb. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 49.

Material: Antimony (Sb) Type: Microetching Method: Chemical etching

Etchant (electrolyte): 30 ml glacial acetic acid, 10 ml hydrogen peroxide (30 %).

Procedure: Few seconds to minutes. Remarks: Sb and Sb alloys.

Etchant (electrolyte): 100 ml distilled water, 30 ml hydrochloric acid, 2 g iron (III) oxide.

Remarks: Sb and Sb alloys. Pb-Sb, Bi-Sn and Bi-Cd alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 49.

Etchant (electrolyte): 30 ml distilled water, 15 ml hydrochloric acid, 50 ml acqueous solution of sodium thiosulfate (16 %), 3 ml acqueous solution of chromium (Vi) oxide (Czichralski's reagent).

Procedure: Add chromium (VI) oxide shortly before use. Chromium (VI) oxide content can be raised.

Remarks: Sb alloys. Grain contrast etch. Toxic.

Etchant (electrolyte): 50 ml distilled water, 50 ml hydrochloric acid. Procedure: 1-10 min.

Remarks: Sb, Bi and their alloys.

Material: Bismuth (Bi) Type: Microetching Method: Chemical etching

Etchant (electrolyte): 95 ml ethanol (96 %), 5 ml nitric acid. Procedure: Few seconds to minutes.

Remarks: Bi-Sn eutectic, Bi-Cd alloys.

Etchant (electrolyte): 100 (100) ml glycerol, 25 (9) ml nitric acid, 25 (9) ml glacial acetic acid. Procedure: Few seconds to minutes.

Remarks: Sb-Pb alloys.

Material: Bismuth (Bi) Type: Microetching Method: Chemical etching

Etchant (electrolyte): 100 ml distilled water, 5 g silver nitrate. Procedure: Few seconds to minutes.

Remarks: Bismuth

Material: Cadmium (Cd), thallium (Tl) Type: Microetching

Etchant (electrolyte): 98 ml ethanol (96 %), 2 ml nitric acid. Procedure: Few seconds to minutes.

Remarks: Cd and Cd alloys, Tl.

Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p.50.

Material: Cadmium (Cd), thallium (Tl) Type: Microetching

Etchant (electrolyte): 100 ml distilledwater, 10 g chromium (VI) oxide. Procedure: 1-10 min.

Remarks: Cd and solder alloys containing Cd. Tl. Toxic.

Reference: G.Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 50.

Material: Cadmium (Cd) Type: Microetching Method: Chemical etching

Etchant (electrolyte): 100 ml distilled water, 25 ml hydrochloric acid, 8 g iron (III) chloride.

Procedure: Few seconds to minutes. Remarks: Cd-Sn and Cd-Zn eutectics.

Material: Cadmium (Cd), thallium (Tl), indium (In) Type: Microetching

Etchant (electrolyte): 40 ml distilled water, 10 ml hydrochloric acid (40 %), 10 ml hydrogen peroxide (30 %).

Procedure: 5-10 s.

Remarks: Cd, In, Tl, In-Sb and In-As alloys.

Material: Indium (In) Method: Microetching Type: Chemical etching

Etchant (electrolyte): 100 ml ethanol (96 %), 5 ml hydrochloric acid, 1g picric acid.

Procedure: Few seconds to minutes. Remarks: In and In rich alloys.

Material: Cadmium (Cd), thallium (Tl Type: Microetching

Etchant (electrolyte): 100 ml distilled water, 200 ml glycerol, 200 ml phosphoric acid.

Procedure: 5-10 min, 8-9 V dc, Cd cathode. Remarks: Cd, In.

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Material: Cobalt (Co) Type: Macroetching Method: Chemical etching

Etchant (electrolyte): 50 ml distilled water, 50 ml hydrochloric acid. Procedure: 30-60 min, hot. Rinse in hot water.

Remarks: Co-Cr alloys, also Stellite.

Etchant (electrolyte): 100 ml distilled water, 10 ml nitric acid, 50 ml hydrochloric acid, 10 g iron (III) oxide.

Procedure: Swab. Rinse in warm water.

Remarks: Co-25Cr-10Ni-8W, Co-21Cr-20Ni, and Co-3Cr-3Mo-1Nb alloys, other stellites.

Etchant (electrolyte): 25 ml distilled water, 50 ml hydrochloric acid, 25 ml nitric acid.

Remarks: Co-Ni-Fe base alloys. High temperature alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 51.

Material: Cobalt (Co) Type: Microetching Method: Chemical etching

Etchant (electrolyte): 100 ml methanol (95 %), 1-100 ml nitric acid. Procedure: Few seconds to minutes. Toxic.

Remarks: Pure Co, Co-Fe alloys, WC-TiC-NbC-Co type cemented carbides.

Etchant (electrolyte): 15 ml distilled water, 15 ml glacial acetic acid, 60 ml hydrochloric acid, 15 ml nitric acid.

Procedure: 5-30 s. Wait at least 1 h before use. Toxic.

Remarks: Pure and low alloy Co. B alloys. Ti alloys, and Co-Mn alloys. WC-TiC-TaC-Co type cemented carbides. Grain boundary etch.

Etchant (electrolyte): 100 ml hydrochloric acid, 5 ml hydrogen peroxide (30 %).

Procedure: Few seconds. Use only fresh. Toxic.

Remarks: Wear resistant alloys. Alloys used for Co base cutting tools. Supperalloys.

Etchant (electrolyte): 100 ml distilled water, 20-30 g ammonium persulfate.

Remarks: Cemented carbides and other Co base alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 52.

Etchant (electrolyte): 100 ml distilled water, 10 g potassium hydroxide, 10 g potassium ferricyanide.

Procedure: Few seconds to minutes. Toxic.

Remarks: WC-TiC-TaC-Co and WC-NbC-Co type cemented carbides. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 52.

Etchant (electrolyte): 75 ml hydrochloric acid, 25 ml nitric acid. Procedure: Few seconds to minute. Use fresh only. Toxic. Remarks: WC-TiC-NbC-Co type cemented crabides. Co-Pt alloys. Reference: G. Petzow, Metallographic Etching, ASM (American Society for Metals), 1978, p. 52.

Etchant (electrolyte): 100 ml distilled water, 100 ml hydrochloric acid, 200 ml methanol (95 %), 5 ml nitric acid, 7g iron (III) chloride, 2 g copper (II) chloride.

Procedure: 10-15 s. Immerse or swab. Remarks: Co-Fe alloys. Magnetic alloys.

Etchant (electrolyte): 100 ml distilled water, 50 ml nitric acid. Procedure: 90 s.

Remarks: Co-Ga alloys.

Material: Cobalt (Co) Type: Microetching Method: Physical etching

Etchant (electrolyte): Hot etching in air. Procedure: 30 min, 400-450 C (750-850 F).

Remarks: WC-TiC-(Ta, Nb)C-Co tye cemented carbides. Carbide phase are easily distinguishable fom binder phase by differences in colors.

Etchant (electrolyte): 100 ml distilled water, 1 ml glacial acetic acid, 1 ml nitric acid.

Procedure: Few seconds. Remarks: Co-Sm alloys.

Material: Cobalt (Co) Type: Microetching Method: Electrolytic etching

Etchant (electrolyte): 100 ml distilled water, 3 g potassium hydroxide, 2 g sodium carbonate.

Procedure: 10 s, 3 V dc, stainless steel cathode. Increase of sodium carbonate content increase removal rate of WC phase. Deposit removed with diluted hydrochloric acid.

Remarks: Cemented carbides with Co binder phase.