Tin allows can be difficult to prepare because it is very soft and distortion to the microstucture can easily occur. If not removed this distorted layer hides the true microstructure. In addition, if any excessive heat occurs during preparation the microstructure can also be masked by surface recrystallized. Proper preparation requires minimizing damage. For tin and tin alloys, alternating between polishing and etching is often required in order to remove the damaged microstructure. The recommended etchant is 2% nital (2 ml nitric acid in 100 ml methanol or ethanol); etch for only a few seconds before repolishing.
SECTIONINGTin-Antimony-Copper (hard tin), 100X, 2% nital etchant for 2 seconds |
Tin-bismuth alloy, 200x, etchant 2% Nital |
CAUTION:Safety is very important when etching. Be sure to wear the appropriate protective clothing and observe all WARNINGS on chemical manufacuters SDS (Safety Data Sheets). Also review the COMMENTS and CONDITIONS Section for each etchant.