MUELLER Alloy 4640 (formerly MBCo Alloy 203) is a classic marine alloy known as Naval Brass. It contains nominally 0.75% tin which has made it the most widely used marine alloy. It is suitable for both salt and fresh water applications. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fatigue. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Cu-366. Producer or source: Mueller Brass Company.