Aluminum is a metal that weakens slightly on the surface. By mechanical polishing, it is easy to eliminate this superficial oxidation and give the object brightness comparable to that of chromium. The aesthetics is thus improved, the element is highlighted and in a sustainable way.
For safety, wear gloves to hold the room and glasses and a dust mask. Work outdoors or in a well-ventilated room.
Hold the part firmly when applying it to the disc, without exerting too much pressure. In freehand polishing, determine the best angle of attack to prevent the disc from fading.
If in everyday life, many objects can be polished, it is especially in the context of the renovation of old vehicles that this process is used. In the 60s, many elements hubcaps were aluminum. There were also more massive parts, such as the rocker covers or depression bells of the famous SU carburetor equipping many British cars, for decades, from the Bentley to the Mini. The chemical mechanical polishing equipment parts come as very useful there.
The polishing set
Several retailers (ALP Diffusion for example), market kits including:
- Three sanding discs 110 mm: gray sisal for brushing, a cotton brown stitched for refining, a pink cotton free for brightening.
- Three abrasive dough loaves: gray, brown and pink to be used respectively with each disc color.
- A conical drill bit to be mounted on a drill.
The conical tip with several stages is fixed by simply screwing on the central hole of a disk flange. Its cylindrical part is clamped in the chuck of a drill with a minimum power of 700 W, rotating at 3000 rpm.
To polish a fairly massive piece such as the SU bells, the drill is held in an eye mount bracket (Wolfcraft type). The discs are necessarily used in the order – gray, brown, pink – and must be “formed” when they are new by rotating them on a piece of flat iron. A dough roll, applied a few seconds on the heated wafer, allows garnishing it with abrasive material. If the dough goes to dust, repeat the previous operation.
Then bring the piece against the sisal disc passed to the blue paste and move it laterally in cross passes without parking in the same place. Continue similarly with the brown and pink discs garnished with the corresponding pasta.
The first disc removes deep scratches and gives a brilliant appearance, the second removes the microrayures left by the previous and the third brings the final brilliance. When the disc is black, dirty and smooth, clean it with a wire brush, while leaving it rotating.
The drill with its disk is then moved obliquely on the piece, here a shell. This light element is held fixed by screwing it temporarily on a piece of wood.