The easiest way to understand how a metal polish works is to think of it as liquid sandpaper. A polish is generally comprised of an abrasive dust suspended in a liquid to form a slurry or a paste. The liquid constituent acts as a lubricant. Different abrasive dusts are used depending upon the intended substrate to be polished. These dusts are selected based on their particle size and on their hardness.
To this abrasive action, some polishes include chemical compounds—mild acids or bases—that are intended to chemically dissolve the most common forms of oxidation specific to the target metals.
Additionally, to preserve the just-polished, chemically clean surface from immediate re-oxidation, most polishes include various forms of wax emulsions in the formulations.
Depending upon the type of metal, different polishes are more appropriate.
Polishes for Aluminum:
Fresh-machined aluminum parts—wheels, billet parts, sheetmetal skins—have a natural beauty. Unfortunately, raw aluminum also has a natural characteristic of growing an aluminum oxide coating when exposed to air. This oxide layer is porous and when other contaminants are present, this oxide layer grows with a mottled appearance and is very difficult to remove.
The finest and easiest-to-use aluminum polish we have seen yet is a product called “Heavy Metal.” This cleaner is comprised of an abrasive dust carried in a solvent into which a wax emulsion is dissolved. The product is water-thin making it easy to apply. Through the abrasive action, lubricated by the presence of the solvent, the oxide layer is effectively removed. The abrasive and oxide residues are wiped away leaving behind the wax layer to protect the surface from immediate re-establishment of the oxide layer.
Polishes for Stainless Steel:
Note that most so-called “Stainless Steel Cleaners” are actually degreasers rather than polishes as we have defined them above. They are primarily intended to remove kitchen grease and fingerprints from the grained stainless steel finishes found on so many kitchen appliances.
A true polish for stainless steel is essentially of the same composition as used for aluminum—just with a harder abrasive dust in the matrix.
Polishes for Brass, Copper & Silver:
Due to the chemically active nature of these metals in the presence of moisture and their penchant for growing the various forms of oxidation (silver tarnish, copper patina), these polishes, in addition to the ever-present abrasive dust, generally contain a chemical constituent that will dissolve these oxides.