Common Etchants Reference Guide
Comprehensive quick reference guide to common etching reagents and their applications for metallographic sample preparation. Includes both PACE Technologies pre-mixed solutions and other commonly used etchants in practice.
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Get a comprehensive printable reference guide with common etchants organized by material type, including compositions, applications, and etching times. Includes both PACE Technologies products and other widely used etchants.
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Note: Etchants marked with (Available from PACE Technologies) are available as pre-mixed solutions. Other etchants are commonly used in practice and can be prepared in-house.
Carbon Steel / Low Alloy Steel
2% Nital
(Available from PACE Technologies)Composition: Ethanol, HNO₃ (2%)
Application: General purpose, reveals ferrite grain boundaries and pearlite. Ideal for softer steels.
Time: 5-30 seconds
3% Nital
(Available from PACE Technologies)Composition: Ethanol, HNO₃ (3%)
Application: Standard concentration for most carbon steels. Most commonly used.
Time: 5-30 seconds
Picral
(Available from PACE Technologies)Composition: Ethanol, Picric acid (2-4g/100ml)
Application: Reveals cementite and pearlite, does not attack ferrite boundaries. Superior for pearlite structures.
Time: 10-60 seconds
Sodium Metabisulfite (10%)
Composition: Na₂S₂O₅ (10g), Water (100ml)
Application: For revealing prior austenite grain boundaries in quenched and tempered steels
Time: 10-30 seconds
Stainless Steel
Vilella's Reagent
(Available from PACE Technologies)Composition: Picric Acid (1g), HCl (5ml), Ethanol (100ml)
Application: General purpose, most versatile for stainless steel. Works well for most grades.
Time: 5-30 seconds
Adler's Etchant
(Available from PACE Technologies)Composition: Cu(NH₄)Cl₂ (9g), HCl (150ml), FeCl₃ (45g), DI Water (75ml)
Application: 300 series austenitic stainless steels and superalloys
Time: 5-30 seconds
Aqua Regia
Composition: 3 parts HCl : 1 part HNO₃
Application: For austenitic stainless steels. Very aggressive - reveals grain boundaries and twin boundaries. Handle in fume hood.
Time: 5-15 seconds
Aluminum & Aluminum Alloys
Keller's Reagent
(Available from PACE Technologies)Composition: DI Water (190ml), HNO₃ (5ml), HCl (3ml), HF (2ml)
Application: Standard etchant for aluminum and aluminum alloys. Reveals grain boundaries and precipitates. Most common.
Time: 10-30 seconds
Tucker's Reagent
Composition: HCl (45ml), HNO₃ (15ml), HF (15ml), Water (25ml)
Application: For revealing grain structure in aluminum alloys, especially heat-treated materials
Time: 15-45 seconds
Nickel Alloys
Inconel Etchant
(Available from PACE Technologies)Composition: Multiple Solutions (HNO₃, HCl, H₂O₂)
Application: Macro etch for nickel alloys including Inconel. Use fresh solution only.
Time: 10-30 seconds
Glyceregia
Composition: HCl (15ml), Glycerol (10ml), HNO₃ (5ml)
Application: For nickel-based superalloys. Reveals gamma prime and other phases. Excellent for superalloys.
Time: 10-30 seconds
Safety Guidelines
- Always work in a well-ventilated area or fume hood
- Wear appropriate PPE (gloves, goggles, lab coat)
- Handle acids and corrosive chemicals with extreme care
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