I have seen some stainless steel rifles that you can basically dunk in water, require no cleaning, etc and perform time after time. If SS is so good why are most weapons made of aluminum parts which is then anodized coated black? If you dunk these weapons in water will they rust? ThanksTheir is no such thing as a corrosion proof metal. It\'s just corrosion resistant. Some more than others. And regardless it\'s going to have to be cleaned. When it comes to parts being made out of aluminum instead of steel it boils down to basically weight. Weight saving is a big thing nowadays and while aluminum is up to 5X more expensive its also 3x lighter. Also most aluminum parts on firearms are either low or no stress. Any high stress parts such as the bolt, chamber and barrel has to be made from a steel. No getting around it as aluminum wears out from those types of stresses faster.Stainless Vs Aluminum PropThe components of guns that have to deal with the heaviest forces and pressures (receivers, barrels, bolts) are almost always some form of steel, not aluminum. Stainless steels are MORE EXPENSIVE, consequently other equally strong but less expensive steels is used and coated with a protective finish, like bluing or parkerization (steel cannot be anodized). Sometimes steel is chromed or nickel coated to look like stainless steel. Aluminum is used in frames and lower receivers and possibly other smaller parts, and in fact aluminum is actually MORE corrosion resistant than stainless steel. Generally the alternative material to aluminum these days is some form of polymer. For example, while sig sauer uses aluminum frames on their handguns, Glock uses polymer frames. Stainless steel used in guns will rust if you don\'t take care of it. Blued, parkerized, and other protective finished steels will not rust under most conditions if they are taken care of. Otherwise all the armies of the world would have very rusty guns.You may pick up as much as three or four MPH with a stainless prop. The reason is that aluminum props will flex a bit under power and decrease the pitch where SS props won\'t. The downside of a stainless prop is that if you hit something solid at speed, you will likely tear out your lower unit. I have owned a bunch of boats and never put a SS prop on any of them. It just wasn\'t worth the chance for that potential big repair bill. My advice? Have your aluminum prop rebuilt. It\'s fairly economical.Stainless steel will rust.. It does have small amounts of carbon in it It just takes longer... Than carbon steel to stain Aluminum works for low stress parts ... AR lowers, hand gun frames If the part is stressed or needs wear resistance it generally is made of tool or ordinance grade steel-carbon or stainlessOther related question