Stainless Steel Etchants
Etching stainless steels can be somewhat difficult due to the anti-corrosive nature of stainless steel. Austenitic or 300 series stainless steels typically have higher chrome as well as a significant amount of nickel (e.g. 304 stainless steel - 18% chrome, 8% nickel) which makes them harder to etch. Martensitic or 400 series stainless steels are easier to machine, however, they are not as corrosion resistant so they are easier to etch.
Sample Preparation: Stainless steels must be properly prepared to reveal the true metallographic microstructure. A number of recommended procedures can be found at the following links:
http://www.metallographic.com/Procedures/Stainless%20Steel%20Description.htm
http://www.metallographic.com/Brochures/Met-Manual-2b.pdf
CAUTION: Safety is very important when etching. Be sure to wear the appropriate protective clothing and observe all WARNINGS on chemical manufacturers SDS (Safety Data Sheets). Also review COMMENTS Section for each etchant.
|
Etchant |
Conc. |
Conditions |
Comments |
Adlers 300 Series |
45 grans 9 grams 150 ml 75 ml |
Immerse for several seconds. | A very effective etchant for 300 series, austenitic, duplex stainless steels |
Carpenter 300 Series |
8.5 grans 2.4 grams 122 ml 122 ml 6 ml |
Immerse for several seconds. | A nice etchant for 300 series, austenitic, duplex stainless steels |
| Kalling' No. 2 Cupric chloride Hydrochloric acid Alcohol |
12 grams 20 ml 225 ml |
Immerse or swab - seconds to minutes | For 400 series or martensitic stainless steel |
|
Modified Murakami's |
|
1 second to several minutes by immersion or swabbing |
Mix potassium hydroxide into water before adding K3Fe(CN)6. |
|
Hydrochloric acid |
20-30 ml |
Immerse at room temperature for 1-4 minutes |
Color etching. Colors carbides and gamma prime phase in heat resisting steels |
|
Ammonium bifluoride |
20 grams |
Immersion at room temperature for 1-2 minutes |
Color etching. Etching of austenitic stainless steel and welds. Reveals delta ferrite in welds. |
 |
431 Stainless Steel, etched with Modified Murakami's, Mag. 400X (DIC) |
