The ingredient in all these rust busters is phosphoric acid. You can get the straight stuff from auto body supplies. The gel in the commercial stuff is to make it stay wetted on the surface longer.
The phosphoric acid in Coke and many other soft drinks is for the taste. Ummmm, so good and refreshing.
Wonder if it cleans out rust in the body? What else? How about teeth and bones? Which is higher on the activity chart, phosphorus or calcium? Are there any natural food with high concentrations of phosphoric acid? What does the body do with the excess phosphate?
I don't know the answers to these questions. I'm just a retired electrical
engineer, but I'm thinking I should know the answers.