Table 1-3.-Surface Colors of Some Common Metals

Duralumin

One of the first of the strong structural aluminum alloys developed is called Duralumin. With the development of a variety of different wrought-aluminum alloys, a numbering system was adopted. The digits indicate the major alloying element and the cold-worked or heat-treated condition of the metal. The alloy, originally called Duralumin, is now classified in the metal working industries as 2017-T. The letter T indicates that the metal is heat-treated.

Alclad

This is a protective covering that consists of a thin sheet of pure aluminum rolled onto the surface of an aluminum alloy during manufacture. Zinc chromate is a protective covering that can be applied to an aluminum surface as needed. Zinc chromate is also used as a primer on steel surfaces for a protective coating.

Monel

Monel is an alloy in which nickel is the major element. It contains from 64% to 68% nickel, about 30% copper, and small percentages of iron, manganese, and cobalt. Monel is harder and stronger than either nickel or copper and has high ductility. It resembles stainless steel in appearance and has many of its qualities. The strength, combined with a high resistance to corrosion, make Monel an acceptable substitute for steel in systems where corrosion resistance is the primary concern. Nuts, bolts, screws, and various fittings are made of Monel. This alloy can be worked cold and can be forged and welded. If worked in the temperature range between 1200°F and 1600°F, it becomes "hot short" or brittle.

K-Monel

This is a special type of alloy developed for greater strength and hardness than Monel. In strength, it is