The gas tank cleaning and coating kit I bought years ago used phosphoric acid as the cleaner. Overnight it cleaned and etched my Harley tank inside pretty well. It's not a strong acid as it's also a main ingredient in most soft drinks. Since it's pretty benign it might be worth a try for parts cleaning.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.