It’s not exactly a mirrored surface! How to polish aluminum parts for adults to achieve a moist and pure look

How to

When we think of polishing aluminum parts, the first thing that comes to mind is a mirror finish.

However, when it comes to customization and restoration, a shiny, spotless finish is ideal, but on the other hand, there are times when you may not be able to get that kind of shine for your car in your daily life.This is when you should try "moist polishing".
There are many ways to polish aluminum surfaces to remove dullness and prevent them from shining too brightly, so it's a good idea to learn this technique for a wide range of applications. It comes in handy.

Anodized aluminum finish is also a form of oxidation

Anodized aluminum finish is also a form of oxidation

It is very important to prepare for the polishing process.The trick is not to use coarse sandpaper because it's hard to remove the abrasion.This time, we used sandblast #240.

From the engine to the undercarriage, there are many aluminum parts used on bikes, and the manufacturing methods and surface treatments vary.Aluminum has a tendency to oxidize easily (i.e. rust easily), so anodized aluminum is widely used to prevent further oxidation by forming an electrochemical oxide film on the surface of the material in advance.

Often used for surface treatment of swing arms mainly made of extruded material and top bridges machined from block material, anodized aluminum can also be used to color the material by using dyes in the oxide film formation stage.Unlike paint, anodized aluminum is useful as a customization method because the color is applied while retaining the appearance of the aluminum material.

Another surface treatment unique to aluminum parts is "polishing".While painted steel parts are polished on the painted surface, aluminum parts are polished on the material itself, which brings out the unique luster of the metal, and the shiny, lustrous shine called buffing or mirror finish is also an attractive feature of aluminum parts.

By the way, when it comes to polishing aluminum parts, not anything made of aluminum can shine.The oxide film of anodized aluminum is very hard, and polishing agents can only polish the film, not the aluminum material. Also, many people know that painted aluminium materials such as brake calipers do not shine when they are polished with aluminium polish.

In other words, polishable aluminum parts are those that are not anodized and not painted.


  • Aluminum parts are widely used in both old and new motorcycles.
  • Polishing of parts without anodizing and painting is possible.

Polishing of aluminum parts from coarse to fine

Polishing of aluminum parts from coarse to fine

Polishing with #400 non-woven abrasive while spraying anti-rust lubricant.If the abrasive is dry, you may get deep scratches on the surface, so it is better to polish with lubricant while sliding it. Sandpaper is fine, but if the shape of the part is complicated, non-woven cloth is recommended to follow the shape better.

Polishing of aluminum parts from coarse to fine

As the non-woven fabric bites and scrapes the surface of the part, the lubricant characteristic of aluminum polishing begins to stain black.Repeating the process of wiping with a rag and spraying the lubricant and polishing will remove the roughness of the sandblasted finish and give it a shiny appearance.

Many aluminum parts that do not have an anodized or painted finish may or may not glow easily depending on the composition of the aluminum alloy, but in many cases they will shine when polished. Aluminum is a metal that oxidizes easily, so simply removing the oxide film will give it a shine.

When you get down to that luster, you get a mirror finish, but polishing aluminum doesn't mean that everything is mirrored.In many cases, it is better to polish the bike as a whole with less gloss if it is a normal polishing range, even if it is a custom bike.

Here is an example of a moist polish using the drum brake panel of a 1960s small displacement car as an example.

Parts that have been stained with rust or oil during their immobilization period are first degreased and cleaned to make sure they are ready for polishing.Try polishing them with a metal polishing chemical and if the shine is immediately apparent, continue working on them.In many cases, however, you shouldn't be able to suddenly polish parts that have been exposed to wind and snow for years with abrasive chemicals.

Like files and sandpaper, abrasives have the same grinding function to remove metal surfaces, but the so-called "coarseness" is much finer than that of sandpaper, so the aluminium material does not stand up to the teeth.

Therefore, the first step is to polish the surface of the material with sandpaper, but again, the selection of the coarseness of the sandpaper must be carefully considered.Coarse paper, such as #120 or #180, will easily grind the surface of the aluminium, but it is necessary to work on removing the scratches caused by this process.The finer you go, from 120 to 240, 400 to 600, 800 to 1,000..., the deeper the shine, the closer to a mirrored surface you will get.

However, no matter how much time and effort you put into achieving a mirror finish, you will never have enough time and effort.There are professionals who specialize in buffing and polishing, so it may be wise to give up after a certain amount of time.


  • Preparation of the groundwork for polishing aluminum parts is necessary.
  • If you want to achieve a mirror finish, start with coarse paper.

The key to a moist polish is not to make the abrasive scratches too deep

The key to a moist polish is not to make the abrasive scratches too deep

Further polishing is done by substituting chemicals for aluminum polishing.Since the sandblasting abrasive is not completely crushed, the matte finish is still there, but the luster has been deepened.If you want a more mirror-like finish, narrow the interval between the coarse and fine grains to make the surface of the material gentle and uneven.

The key to a moist polish is not to make the abrasive scratches too deep

There are still some clear signs of scrubbing with non-woven cloth, but the shine of aluminum parts is very attractive.The surface finish of the parts will vary depending on the type of bike and the direction of the bike's construction, but if you want a subtle finish without excessive dressing up, try moist polishing.

On the other hand, if you're aiming for a moist polish, there's no need to use a paper that's too coarse.In this case, the sandblasted brake panels were polished by spraying #400 equivalent non-woven abrasive with a lubrication spray.This won't remove the abrasive grain of the sandblast, so even if the surface is polished with a non-woven cloth, it won't be a mirror surface.

However, the shine on the surface while the substrate is cloudy will give you a metallic luster without too much shine from a moist polish.The luster of aluminum, even when painted and not mirror-finished, may seem half-hearted depending on how you look at it, but it doesn't give an unbalanced impression that only a portion of the surface will shine extremely brightly when assembled into a car body (although a mirror-finished finish is a better match for a fully plated and fully polished custom car).

The most important point is not to make the grain of the polishing media too coarse.

If you can't use a metal polishing chemical to grind dirt and corrosion, try #1000, then 600 and a fine paper first, and if the grinding is effective, use no coarser grit than that to evenly polish the surface, and you'll get a very different, production car-like finish than a mirrored one.Still, if you can polish with paper or non-woven cloth, the effect of the abrasive will be clear, so if you want a moist and shiny surface, you should try it.


  • A moist polish won't be too coarse.
  • Once the groundwork is done, the abrasive will work.

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