alkaline-acid pickling of Inconel, (I don't know if it was ever meant for steel) this Kickapoo juice is hotter than a pistol, as just a dangerous. I don't recommend anyone using it, for reference only. 

steel tank, 180 degrees F
NaOH - 18 ounces
sodium carbonate - 18 ounces
KMnO4 - 7 - 11 ounces
Water 1 gallon 

acid pickling solution
wooden tank (I'm not kidding, this is OLD) 180 degrees F
66 degree baume H2SO4 16 ounces
Sodium Nitrate 8 ounces
copper sulphate or copper nitrate 1.5 ounces water 1 gallon. 

It's these kinds of solutions which make me glad that there are now proprietary solutions around.