Aluminum Characteristics
Aluminum is a light-weight metal with a bright silvery
luster. Small amounts of other metals are added to
aluminum to make harder alloys for most uses. Its
affinity for oxygen makes it resistant to corrosion and
attack by most chemicals. Most aluminum used in visible
parts of appliances is lacquered or otherwise coated,
anodized or painted.
Aluminum reacts with air to grow its own thin oxide
coating very fast. This hard, dark gray coating protects
the metal. It's found on all bare aluminum surfaces,
including utensils which, if rubbed on a counter or range
top, or other material, makes a dark gray mark. If washed
off the outside of the pan, it quickly forms again. A
commercial process, called "anodizing", thickens this coat
and often colors it. Anodizing does not rub off. A special
anodizing process produces a very hard, dark gray finish
on professional type cookware.