After sandblasting aluminium, varying applications such as chemical polishing or electrolytic polishing will increase the shine and brightness of the finished product making it more attractive and, in some cases, durable. Chemical polishing works by applying selective chemical agents that react with the aluminium to remove uneven surfaces, or scars and scratches from wear. It can also be used as an “etching” agent, often the first step in a coating process..
In electro chemical polishing more usually known as electropolishing the work piece is held in an electrolyte bath and an electric current passed through it which oxidises and dissolves the surface metal. The raised portions of the metal [hills,] caused by scratches, war of lumps are oxidised faster than the surrounding surface [valleys] so the net result is the surface is reduced to one [relatively] even field. Hover, at higher magnification, ups and downs and other minor irregularities can still be observed, However, to the human eye, the surface looks smooth.
If the aluminium product is destined for a coating treatment, such as galvanising or anodising to increase its weather or concision resistance or just to beauty the product, the small imperfections, invisible to the naked eye, form an ideal base for the coating to key into or adhere to.
In most reported literature at home and abroad, the aluminium surface polishing process can be summed up in no more than three stages: mechanical polishing, chemical polishing and electrochemical polishing.