Stainless steels-Color etching

Material: Stainless steels
Type: Micro
Method: Chemical etching
Etchant (electrolyte): Stock solution: 1:5 v/v hydrochloric acis (35%) and distilled water, 100 ml of the stock or stock solution: 1:2 or 1:1 or 1:0.5 v/v hydrochloric acid (35%) and distilled water. 100 ml of stock solution plus 0.6-1 g potassium metabisuifite. Optional addition of 1 -3 g ferric chloride or 1 g cupric chloride or 2-10 g ammonium bifluoride solution plus 0.5-1 g potassium metabisulfite.
Procedure: Immersion at room temperature for 30-120 s. Keep specimen moving during etching. When good coloration is not produced and when etching heat-resisting steels, use reagent (stock solution: 1:2 or 1:1 or 1:0.5 v/v hydrochloric acid (35%) and distilled water, 100 ml of stock solution plus 0.6-1 g potassium metabisulfite. Optional addtions of 1-3 g ferric chloride or 1 g cupric chloride or 2-10 g ammonium bifluoride) (1:1 or 1:0.5) and a longer etching time.
Note: Color etching. Etching of austenitic stainless steels. Colors the austenitic matrix, leaving carbides and nitrides white (uncolored).
Source: E. Beraha and B. Sphigler, Color Metallography, American Society for Metals (ASM), Metals Park, Ohio 440073, USA, 1977. p. 62.







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