Is spanking considered child abuse in Arizona?

My ex is trying to get me on child abuse charges for spanking our son. He’s 6 years old and gets into everything. I spank him as a form of punishment and I was raised the same way. I do not hurt him or leave marks. I think it’s the best way to teach him. His mother says all spanking is illegal and is child abuse. I live in Phoenix, what is the law here in Arizona regarding corporal punishment/spanking your child? I think she is using this as a way to take shared custody of our son from me and I want to know the law before I deal with her on this issue.