The problem with cleaning a dial using any acid or even Windex is that you strip away the top coat. Yes, there is the potential to make it look nice for a while, but removing the top coat will expose the dial to even worse elements and eventually ruin it completely. If you're gonna attempt to clean it, you should know it's gonna work and you should have a way to put a protective lacquer back over it after it dries. Otherwise, buy a new watch if you want a watch that looks like new.