This gives hot dip the big advantage of being the lowest cost way to blue a gun. And for this low cost, we must admit, hot dip gives at least satisfactory results. It does protect the gun, if the owner does his her part, keeps the gun clean and oiled. But there are a couple disadvantages to hot dip blue, that to my way of thinking, pretty much completely wipes out its low cost advantage. Hot dip blue has earned an excellent reputation for its ability to cover and hide scratches, pits, and blemishes, in gun metal.
Hot dip looks like a coat of something painted on the gun metal.
Questions like this can make the gun a no sale, even at a give away price. My firm opinion on this comes from many years experience, buying and selling guns in the collector gun marketplace. Rust blue does not fill in number and letter markings. Rust blue never looks like a coating of something on the steel. It's been said about a beautiful oil finish on wood, the oil ain't on the wood, it's in the wood.