I'm a welding instructor at the high school level. I'm going to collaborate with one of the science teachers to teach a class about welding and etching the weld samples. My students are going to make some fillet welds in a few tee joints. We are then going to cut sections out of them and sand the face smooth for the etching process. I would like to have some cracking of the welds or other discontinuities so they will show up in some of the sections. I have thought about using cast iron and welding it with a 6010 rod. We also have some high carbon tool steel that we might weld with something to get it to crack.

Are there any other metal and rod combinations that you could recommend that might cause some discontinuities we would see after the pieces are etched?

What is the best way to go about the etching process?

What kind of acid would be a good choice and what kind of metals would work on?

Are there any safety concerns other than what would be the obvious when handling acids? (Such as the acids reaction to various types of metals.)

I may find that I have more questions the further I get into this project. I personally have never done any etching and I'm trying to help the chemistry teacher figure out how to go about it.

Thank you for you help,
                                  Louis