All that I've noticed are stainless steel.
The brazing on the dhwhes is copper based but doesn't seem to be a problem. (it can plate onto the st st and make it look like it's made of copper, perhaps you saw that?)
Full strength spirits of salts doesn't burn if you wash it off skin quickly. It does fume less if you dilute it but I don't usually bother. You can pour some in and fill up with hot water which speeds it up - in a bucket minor spitting doesn't matter either. (Fully concentrated acid would be different.)
You're unlikely to get hold of Nitric acid cos you can make explosives with it rather easily. Drain cleaner Sulphuric acid is nasty stuff though, it dissolves clothes, legs etc but is less effective on scale.
Kamco FX-2 is Phosphoric acid based and slower/gentler but still works 100%.
