Etchants

MetPrep Ltd are delighted to be able to publish a range of standard etchants.

Our intention is to offer a more comprehensive range of preparation parameters that will enable you to improve your own preparation techniques.

We will also attempt to include any etchants that you would be happy to recommend. Please send the details to Metprep Ltd.

Where water is advised please note that this refers to distilled water in all cases.

Carbon Steels.

Macro Etch	10% Nital 10ml Nitric Acid 90ml Methanol	Versatile macro etch for Iron & Steel. Carburized and Decarburized areas as well as segregation.
Micro Etch	Nital - 1 10ml Nitric Acid 90-99ml Methanol	Most common etchant for Iron, Carbon and Alloy Steels & Cast Irons. Reveals alpha grain boundaries and constituents. The 2% solution is the most common. Use by immersion for up to 60 seconds or by swabbing. The 5-10% solution is used for high-alloy steels.
Micro Etch	Picral 2-4g Picric Acid 100ml Ethanol	Generally used for Iron and heat treated Steels. Recommended for pearlite, marteniste and bainite structures. Use by immersion or swabbing.
Micro Etch	Vilella's Reagent 1g Picric Acid 5ml HCl 100ml Ethanol	General structure of low alloy steels. Reveals prior austenite grain boundaries and bainitic structures.

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Stainless Steels.

Macro Etch	Marble's Reagent 50ml HCl 25ml Saturated aequous solution of Copper(II) Sulphate	Used for revealing general structure.
Micro Etch	Acid Ferric Chloride 10 g Ferric Chloride 30 ml HCl 120 ml Water	Swab etch to reveal general microstructure.
Micro Etch	Kallings Solution 2 g Cupric Chloride 40-80ml Methanol 40ml Water 40ml Hydrochloric Acid	Ferrite and Martensite are darkened. Austenite appears light and carbides are unaffected.
Micro Etch	45ml Glycerol 15ml Nitric Acid 30ml Hydrochloric Acid	For stainless steels with high Cr content. Also Cr-Ni Cast steels.

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Tool Steels.

Micro Etch	Sodium Picrate 1g Sodium Picrate 100ml Water - use boiling	Iron Tungstide is quickly darkened, Iron-Tungsten Carbide is slowly darkened and cementite is unaffected.
Micro Etch	Methanol Regia 5 ml Nitric Acid 10 ml HCl 100ml Methanol	General microstructure.

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Titanium Alloys.

Macro Etch	50ml HCl (1.19) 50ml Water	For differentiation of alpha and beta Titanium.
Macro Etch	30ml HCl (1.19) 10ml HF 10ml Nitric Acid 50ml Water	General purpose macro etch for all Titanium alloys.
Micro Etch	Kroll's Reagent 2ml HF 10ml Nitric Acid 88ml Water	Useful etchant for most Ti based materials, especially Ti-Al-V alloys.
Micro Etch	15ml Hydrogen Peroxide 10ml Aqueous solution of Potassium Hydroxide 80ml Water	Swab etch for Titanium, Ferro-Ti, Ti-Al-V-Sn alloys. Alpha Ti is attacked, beta Ti is left unchanged.

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Copper Alloys.

Macro Etch	50ml Nitric Acid (1.40) 50ml Water	Macro etch for most Copper and Brasses. For grains and cracks.
Micro Etch	5g Iron (III) Nitrate 25ml HCl 70ml Water	General purpose etchant that reveals grain boundaries. Use by immersion.

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Aluminium Alloys.

Macro Etch	Mixed Acids 5ml HF 20ml Nitric Acid 20ml HCl 60ml Water	Useful macro etch for most Al based materials. Reveals grain size, rolling directions and welded joints. - De-smut in 35% Nitric Acid afterwards.
Micro Etch	Keller's Reagent 2.5 ml Nitric Acid 1.5 ml HCl 1 ml HF 95 ml Water	Most common etchant for Al & Al Alloys, except high Si alloys. Swab etch 10 - 20 seconds.

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Nickel Alloys.

Macro Etch	10g Copper Sulphate 50ml HCl 50ml Ethanol 50ml Water	Versatile macro etch for Nickel & Nickel based Alloys. May reveal grain structure in Superalloys.
Micro Etch	Kalling's 2g Copper Chloride 40ml HCl 40-80ml Ethanol	Useful etchant for superalloys and stainles steels as well as Ni-Cu alloys. Good for grain structure. Generally used as swab etch.

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Magnesium Alloys.

Macro Etch	Mixed Acids 5ml HF 20ml Nitric Acid 20ml HCl 60ml Water	Useful macro etch for most Mg based materials.
Micro Etch	Acetic Picral 100g Picric Acid 200ml Methanol 800ml Acetic Acid 800 ml Water	For general structure, reveals grain boundaries and twins. - This solution must be allowed to age for 24 hours
Micro Etch	Citric Acid 10g Citric Acid 90 ml Water	General structure.
Micro Etch	Acetic Picral 2ml Nitric Acid 98ml Methanol	General structure, particularly good for Zr containing alloys.

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Molybdemum & Tungsten.

Micro Etch

36g Sodium Hydroxide 36g Potassium Ferricyanide 100ml Water

Immersion etch for 10secs

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Niobium/ Tantalum Alloys.

Micro Etch	5ml HF 95ml Nitric Acid	Useful etch for Niobium.
Micro Etch	60 ml HF 20ml Nitric Acid 20ml Glycerol	General structure for Niobium.
Micro Etch	50ml HF 10g Ammounium Fluoride	For Tantalum. A much shorted etching time is required when the reagent is hot.