I am wondering if the product metal rescue works? The company shows videos where you just soak something rusted in it and like magic it comes out rust free.

How true is that? Are there any other cheaper/viable solutions?

Also, how do you determine how "deep" rust is? I know that surface rust is rather obvious but some times I have trouble gauging if something is rusted through all the way, pitted etc.?

At $25 a gallon I am rather hesitant to buy this product.