Aluminum is the second most plentiful metal on earth and is one of the most widely used and inexpensive engineering materials. Aluminum's physical properties include good specific strength, high electrical and thermal conductivity, nonmagnetic behavior and excellent resistance to oxidation and corrosion. Like stainless steel, aluminum reacts with oxygen to form an extremely thin oxide layer that protects the underlying material from many corrosive environments.
Aluminum can be divided into two major categories: wrought and casting alloys. Casting alloys, known by three number designations (1xx, 2xx, 3xx, etc.), contain a high level of silicon. The silicon gives the casting alloys low melting points and good fluidity, yet prevents a desirable finish from aluminum polishing.
Wrought alloys, known by four number designations (1xxx, 2xxx, 3xxx, etc.), are shaped by plastic deformation and have significantly different compositions and microstructures from casting alloys. The polishing of wrought alloys produces desirable results. An electropolished wrought aluminum surface will exhibit an improved microsurface and will be free of surface contaminates. The surface will also exhibit a lustrous finish, however, not to the same degree as stainless steel.
To achieve a specific surface finish or highly lustrous finish (i.e. light or heat reflector), aluminum should be mechanically polished. Harrison Electropolishing can mechanically polish aluminum and certify a finish as low as 4 Ra micro-inch.