Posted by Andrew Binz on March 04, 2010 at 14:42:44:
In Reply to: Duplex to carbon weld image contrast posted by D Wilkinson on March 02, 2010 at 09:19:42:
I've had good luck using nital and electrolytic 20% NaOH to generate micrographs of duplex to carbon steel welds. The key is to place the mount with the polished side down in the 20% NaOH solution, but off the bottom of the container, and place the electrode on the back of the duplex specimen. This means that if the specimen is mounted you need to drill a hole in the back. Be sure the electrode only touches the duplex portion of the specimen. Use nital to first etch the carbon steel side, then proceed to etch the duplex. I'm not sure if this will work for macroscopic etching, but it works great for microstructural examination/documentation. Refer to ASTM A 923-08 for more information.