Because of the possible harsh effects on teeth the took out phosphoric acid in colas a couple of years ago, it's not as effective as it once was. People are still cleaning toilets with it though. The best rust removers are very good, I think most large hard ware type stores have an alternative. I have never had anything this rusty to get shiny again though. I have been looking for something that works and I can fill a big container with. If acids are used it needs to be rinsed off, even given a baking soda bath after. It can cause harm later on if not. The way we fuzz with quality lubricant, they once made a big point that machine oil had to be acid free. I'm noting down good rust removal products, and I know at least two of the more known brands are good.