Why etching is done in metallographic tests to reveal the microstructure of a specimen under the optical microscope by achieving contrast in the microstructure. To remove the deformations from grinding and obtain a surface that is highly reflective. To determine the type and rate of corrosion. All of these?
Answers
Etching Is a Chemical or Electrolytic Process Used after Metallographic Grinding and Polishing Procedures. Etching Enhances the Contrast on Surfaces in Order to Visualize the Microstructure or Macrostructure.Etching is used to reveal the microstructure of the metal through selective chemical attack. It also removes the thin, highly deformed layer introduced during grinding and polishing. ... The rate of etching is affected by crystallographic orientation, the phase present and the stability of the region.Since the grain boundaries are attacked at a greater rate than the proper grain due to higher energy content of the grain boundaries. ... Etching occurs when the acid or base is contacted with specimen surface because of the difference in rate of attack of the various phases present and their orientation