#Brass
Brasses are basically an alloy of copper and zinc usually with a predominance of copper. when brasses are in contact with corrosive conditions, for example, atmospheric salt or in salt water, they may dezincify (removal of the zinc phase) leaving a porous, spongy mass of copper. To prevent dezincification, an inhibitor is added to the brass. One such inhibitor is arsenic of which only a small proportion is employed. Brasses have numerous uses, decorative and purposeful. Marine uses include: valves, bearings, condenser tubes, etc. Alloying elements such as tin, aluminium and nickel are frequently employed to improve brasses.With these elements the strength and erosion resistance of brasses can be greatly improved.
# Bronze
Bronze is basically an alloy of copper and tin, but the term bronze is frequently used today to indicate a superior type of brass. It resists the corrosive effect ofsea water, has considerable resistance to wear, and is used for these reasons for many marine fittings. With the addition of other alloying elements, its range of uses becomes extensive Manganese in small amounts increases erosion resistance and forms manganese bronze (propeller brass). Phosphorus, used as a deoxidiser, prevents formation of troublesome tin oxides, improves strength and resistance to corrosion and provides an excellent hard, glassy bearing surface. Aluminium and zinc give aluminium bronze and gunmetal respectively, which are suitable materials for casting.
#Aluminium
This material is progressively supplanting other materials in use for specific items in the marine industry. It resists atmospheric corrosion and its specific gravity is about one-third that of steel. In the pure state its strength is low, but by alloying and by mechanical and thermal treatment its strength can be raised to equal and even surpas that of steel without great loss of ductility. In this form it is used extensively for structura work