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My understanding is that aluminum parts, which most components are made of, have a clear layer of anodising. If you polish, sand or steel wool the parts you are removing this protective layer of anodising and thus exposing the aluminum to corrosive creating elements. Not a wise thing to do if you value your components. It is better to deal with a scratch here or there and leaving it as is.
 

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Here is a bit more information regarding the above:

Anodizing, is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts. The process is called "anodizing" because the part to be treated forms the anode electrode of an electrical circuit. Anodizing increases corrosion resistance and wear resistance, and provides better adhesion for paint primers and glues than bare metal. Anodic films can also be used for a number of cosmetic effects, either with thick porous coatings that can absorb dyes or with thin transparent coatings that add interference effects to reflected light. Anodizing is also used to prevent galling of threaded components and to make dielectric films for electrolytic capacitors. Anodic films are most commonly applied to protect aluminium alloys, although processes also exist for titanium, zinc, magnesium, niobium, and tantalum. This process is not a useful treatment for iron or carbon steel because these metals exfoliate when oxidized; i.e. the iron oxide (also known as rust) flakes off, constantly exposing the underlying metal to corrosion.

Anodization changes the microscopic texture of the surface and changes the crystal structure of the metal near the surface. Thick coatings are normally porous, so a sealing process is often needed to achieve corrosion resistance. Anodized aluminium surfaces, for example, are harder than aluminium but have low to moderate wear resistance that can be improved with increasing thickness or by applying suitable sealing substances. Anodic films are generally much stronger and more adherent than most types of paint and metal plating, but also more brittle. This makes them less likely to crack and peel from aging and wear, but more susceptible to cracking from thermal stress.
 

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Again, I would stay away from polishing your aluminum parts. I made this mistake 15 years ago and render parts god awful ugly. Sure, they look great after you polish them but when you remove the protective layer of anodising you have stripped the compnent bare of the ability to prevent corrosion. And when it begins to corrode it will pit and form small white powdery stuff. Thus, it looks worse than the scratch.

However, if you are not going to use the component in real life situations, and rather hang it on a wall.....then maybe it doesn't matter.

BTW, you can not buff a scratch out of an anodised product. The depth of the scratch often goes deeper than the layer of anodising.

Anytime I see a vintage ad that states they have polished the component to a great shine I quickly rule out the component as having any value or use. It is better to leave the scratch than compromise the component.
 
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