Chem humor
Now, I cannot claim any sort of mastery in chemistry, but I can only imagine these two hitting it off with their respective fields and discussing various chemicals, formulas, compounds, and their reactions. Because I am not a chemist or even a student, I was lazy and simply pulled the butanoic acid structure image straight from the net after looking for an appropriate compound that two robotic aliens would be interested in talking about.
The punchline is sulfuric acid, it's one that works... quite well on metals.