Polishing Aluminum

By Sean Kelly

First, start by cleaning the surface you are going to polish using either soapy water, simple green, a wire brush, Scotchbrite pads or steel wool. Use whatever tool will most effectively remove impurities off of the surface of the metal.. The primary reason for doing this is to keep the equipment you will use later to polish clean. Dirty buffing wheels will scratch the surface and/or lead to a rough or bumpy shine.

Sand the surface with 220, 320, 600, 800, 1000, 1500, 2000 grit 3M Imperial Wetordry sandpaper. You can purchase this at most industrial supply stores, some auto parts stores, and most reliably an auto-body paint supply store. They come in packs of 5 sheets, each about 8 inches square. You will use more of the lower grit per square area than the higher grit. For reference, what is referred to as the low grit range is 40-400 grit, medium grit range is 420-800 grit, and high grit rangfe is 1000-3000 grit. You don't have to use all 3 of the steps, just sand until there are no visible scratch lines. Using an ultra-high grit or multiple grits in each range is optional, but not necessary. A pack of 3M sandpaper contains 5 8x8" square pieces of sandpaper. You will consume much more sandpaper in the lower grit range than the higher ranges, so buy accordingly. Each pack ranges in the four to five dollar range.

Next, obtain the buffing wheels. Lowes, The Home Depot, and Ace Hardware typically carry a wide assortment of wheels and accessories for metal surface preparation. You may find that the store you visit will have an all-in-one kit including an arbor, several wheels and the compound in one package. These are good for beginners or those who do not foresee doing a great deal of polishing work. There are three basic types of buffing wheels. The three types are: center-sewn, "loose" wheels; the spiral-sewn "medium" wheels, and the tightly wound "hard" wheels. One of each will permit a thorough surface preparation. Along with the wheels, one must obtain the buffing compound. There are several types of compound, but only 3 are applicable to non-ferrous metals. The three associated with aluminum are red tripoli, black emery and white rouge. The names deduce the color of the compound and each is associated with a specific part of the process, as well as being tailored to a certain type of buffing wheel.

The tripoli and emery are used in a process called "cutting" which, as suggested by the name, cuts the surface with the compound. When the compound is applied to the surface, it evens out the imperfections in the finish and aligns the reflection of light in a uniform manner. These two compounds, when applied will create a satin finish on the metal. The emery is the harshest of the two cutting compounds, and should be used first, with the most tightly wound buffing wheel. The red tripoli shall be used with the medium wheel. The third compound, white rouge, is used with the loosely wound buffing wheel and is done last. It is the part of the process called coloring. The coloring process will make the material reflective and highly aligned. After the coloring process is completed the surface can then be cleaned and polished. An additional option for extremely high luster is to obtain yet another loosely wound cotton or flannel wheel, or a muslin buffing pad or wheel, or a cotton string buff and apply Jeweler's Rouge to the surface. This is one step above white rouge in finished luster quality, but is not required to obtain a very impressive finish.

The process of applying the compound on the wheel is done by putting the buffing wheel into the grinder or drill, and spinning at a moderate (3000rpm) speed. Hold the compound against the wheel until the working face of the wheel is fully covered. Spin the covered buffing wheel at higher speed, about 4000-4500rpm, and allow the working surface to graze the metal. The surface should end up with a light hazy coat of the buffing compound, evenly distributed across the entire metal surface, and not to the point of the compound being opaque. Continue to apply the buffing wheel to the surface until most of the compound has been worked into the metal and there is a very thing film left on the surface. Wipe this clear with a clean cotton cloth, optionally using hot water or hot soapy water and a clean cotton cloth to dry.

The final step is to polish the surface. This is what reveals the bare unified metal's surface. Meguiars makes a product called Billet Mag Polish which works very well. Apply a small portion to a clean 100% cotton cloth and apply in small circles to the surface. The cloth will develop a black color as it cleans and polishes. Use a clean portion of the cotton cloth for the final wipe. Ensure that all of the polish is cleaned off the surface and what is left should be a clear, smooth surface with no scratches and a very high luster.

The methods described will achieve a shine much higher than the application of sandpaper alone. You need the unified action of the buffing wheels to align the light reflection to attain what appears as an invisible surface. When properly done, only the reflection can be seen off of the surface, conveniently known as a mirror finish. The buffing compounds work on a scale much, much smaller than even 5000 grit sandpaper, is much faster and is a much cleaner operation.

The trickiest part is working the cutting compounds with the stiff wheel. One factor that helps is keeping the compound and wheel heated to the right temperature. Do not press too hard, the wheels will do the work for you. Pressure is traded with speed in the case of the buffing wheels. You can burn the metal if you press too hard, leaving ugly discolored marks. Keep one compound on one wheel, and do not apply more than one compound to a single wheel. Keep the wheel perpendicular to the metal on the rotational plane, and travel only in the axis of rotation. Do not cross paths or do patterns with angled overlaps. Clean the surface between applications of compound to attain the best result. Keep the wheel clean and loaded with compound, and frequently run a hard-bristled brush over the rotating wheel to keep the fibers separated and soft. Do this with the brush along the axis of rotation. Also once a wheel has been sitting for a while and cools off, the compound left on the wheel will be hardened and not do its job well. Clean off the wheel with a wire brush and reapply the compound. Also do not compound sit on the surface, once cooled it becomes difficult to finish and will have to be cleaned off with hot water or other methods.

In the end, the results are worth the time, effort and mess. The method will take practice, but is not hard and once experienced, one can apply all three compounds and have a surface ready for polishing in a matter of a few minutes. Always do the first practice application on a non-visible area before attempting to polish a visible surface.

Summary

Parts needed:
  • Sandpaper:
    • 3M Imperial WetorDry
    • 220-2000 grit, your choice, at least one of each range
  • Cotton rags:
    • 100% cotton, available at auto paint supply shops for $10/10lbs
  • Buffing wheels:
    • 4inch plain cotton:
      • Tightly Wound
      • Medium Wound*
      • Loosely Wound
    • Drill, angle grinder that adapts the above wheels:
      • Minimum 2500RPMs
    • Buffing Compounds:
      • Black Emery
      • White rouge
      • Red tripoli
      • Jeweler's Rouge*
    • Stiff wire brush
    • Meguiars Mag/Aluminum Polish
  • Eye protection
  • Ear Protection
Steps:
  1. Clean
  2. Sand
  3. Cut (Emery/Stiff wheel)
  4. Buff (white rouge/medium wheel)
  5. Buff (Red Tripoli/loose wheel)
  6. Polish (Jeweler's Rouge/loose or muslin wheel)
Method:
  1. Apply Rouge to wheel
  2. Apply a first, sparse coat once over select area to spread compound.
  3. Press the buffing wheel lightly against the surface with the axis or rotation until compound is gone and a cloudy haze forms on the metal surface. Fine lines will be visible from the fabric and motion of the wheel: these are acceptable.
  4. Optionally clean surface between wheels
  5. Using fine wheel, barely make contact with surface, let the compound do the work. A shiny, but not brilliant finish should appear.
  6. Clean and apply Magnesium/Aluminum polish
  7. Wipe clean with a dry terry cloth

To maintain the shine periodically use the Meguiars Billet Mag Polish ; it will keep oxidation off and the high shine. Don't use oil-based polishes or coatings on the surface. Keep all tire shine, degreaser and foaming wheel-cleaning products off. Clean immediately with a cotton cloth if some does spill. Antifreeze is incredibly bad for the shine, you will have to rebuff if you spill any on it due to the porous nature of aluminum. Using a sealant is up to the operator, but is not recommended; consistent upkeep of the surface will yield an incredible shine for a long time.

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CTech
2004