Common etchant for Stainless Steel 304L and Titanium Grade 2

Question

I have Stainless Steel welded to Titanium. I need a common etchant to etch both S.S. and $\ce{Ti}$ so that I can do further analysis (like SEM etc). Right now I'm etching Ti Side separately and S.S. side separately and doing analysis twice, once for each metal. The etchants I'm using are mentioned below:

1. $\ce{HNO3 + 3HCl}$ - for S.S. 304L
2. $5\%~\ce{HCl} + 6\%~\ce{HNO3} + 16\%~\ce{HF} + 74\%~\ce{H2O}$ - for $\ce{Ti}$

Is it possible to combine these two etchants to form a common etchant, or are there any standard etchants available to etch both S.S. and $\ce{Ti}$?

Answer 1

Common etchant for stainless steel is $\ce{FeCl3}$ with $\ce{HCl}$ (up to 3%) heated at 45°C.

The etching solution for $\ce{Ti}$ looks fine.

Answer 2

After several trials, we were able to come up with an etchant, which can etch both Stainless Steel (316L) and Titanium (Ti-6Al-4V) at the same time. We've used the same etchant for Aluminium (1xxx and 6xxx series) and got very good microstructures. The etchant comprises of equal parts of the following :

Ethanol + HCl + HNO$_{3}$ + HF

Note :

1. First mix the acids together (HCl + HNO$_{3}$ + HF) and then mix it with ethanol.
2. The reaction between alcohol and acid is very vigorous. So take precautions as necessary.
3. It takes around 5 minutes for ethanol to completely react with these acids. If you want a fast reaction, then use propanol or methanol instead of ethanol. The final solution should be clear and colorless.