Polishing refers to the various styles of mechanically enhancing or changing the surface of metal. With aluminum, polish finishes can maximize the effect of anodizing by reducing or eliminating extrusion die lines, traffic marks, scratches, and corrosion.
When involving aluminum, polishing should be done before parts undergo any other chemical processing such as chem film, anodize, hard anodize or Eternaprint.
There are two basic types of polish finishes - bright polish (also known as "buff"), and satin polish (also known as "brushed," "line grained," "scratch buff"). Different types of equipment have been developed to allow a range of part shapes and sizes to be polished in either of these two types of finishes, in varying degrees of quality.
While there are no military specifications governing polished finishes, Alcoa Aluminum has developed specs that have been widely adopted throughout the manufacturing and finishing industries, as follows:
To a large degree, the alloy and quality of the raw material when received for finishing determines or limits the results of polishing. Certain aluminum alloys have been developed to accept polishing extremely well, while others do not. Generally, the most common extrusion alloys can be successfully bright polished.
A major advantage of satin polishing is that it can eliminate or hide some surface damage. However, certain severe damage to raw material cannot be adequately removed by polishing, regardless of the method or alloy.
In all cases, metal finishing production must be scheduled so that polished parts are immediately finished with other processes or protected from corrosive humidity or rain.