Copper Silver Microstructure
Etchant - 172
Composition - A. 5 g ammonium persulfate 100 mL water
B. 5 g KCN 100 mL water
Procedure - Use a certified and tested hood—Can give off extremely poisonous hydrogen cyanide.
Precaution Also poisonous by ingestion as well as skin contact. Prepare 1 + 1 mixture of Solutions A and B just before use. (A mixture of 5 drops of each will cover the surface of a 1 in. dia mount.) Immerse 1–2 min.
Etchant - 173
Composition - 50 mL NH4 OH 10–30 mL H2 O2 (50 %)
Procedure - Immerse few seconds to a minute.
Etchant - 62
Composition - 1–5 g CrO3 100 mL HCl
Procedure - Use a certified and tested hood. Vary composition of reagent and aging of reagent after
mixing to suit alloy. Swab or immerse few seconds to a minute.