ALUMINUM ALLOYS FOR CHEMICAL AND LOW TEMPERATURE CARGOES

Although the range of commercially available aluminum alloys is extensive, the list of characteristics desirable in a ship tank or container narrows the choice of alloy to a fairly short list for most applications. The features looked for are principally: 1) compatibility of the metal with the intended contents, i.e., good resistance to corrosion; 2) a satisfactory combination of strength and ductility for the avoidance of notch brittleness and to allow forming operations to be carried out if necessary; 3) good weldability and minimal mismatch between weld and parent metal strengths; 4) resistance to stress corrosion. When a cargo has to be carried at a temperature much different from room temperature, an additional consideration arises; the material properties may vary markedly over the temperature range of interest and the usual practice is to design for the worst possible combination of strength and service conditions. In the case of low temperature tanks, for example, the room temperature strength governs the design. Most applications of aluminum are at room or sub-zero temperatures so that paper concentrates to a large extent on these material properties appropriate to such applications.