Here is a prime example of why you should not use chemicals to clean coins. The images below are two separate 1912 Austria 2 Heller coins. One has it’s original patina and the other someone dumped in muriatic acid. Why do I know it was muriatic acid? The third image is a useless coin I dipped in muriatic acid to see what it would do.
As you can see, the coins turn a dull and ugly pinkish color. The muriatic acid works instantly, so there is no way you can use this chemical to clean your coins without these results. This just further reinforces the fact that you should not clean your coins with chemicals.