Sweet Iron is made from black iron and copper, creating a metal that promotes acceptance and taste in the horse's mouth. Sweet iron will slowly oxidize and rusts. The oxidation has a sweet taste that horses like and which encourages salivation. This metal will almost always discolor. The cheeks and all the joints of the bits are made from stainless steel and will not rust. This is a metal that is highly appreciated by so many horses.  Sweet iron should be wiped dry after every use.