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Polishing Metal [by: Halloweenking]
Hotrodders Bulletin Board: Knowledge Base: Body-Exterior: Articles

Can it be polished? In most cases, yes it can.

When chrome plating or paint is either out of your budget or out of the question, polishing could be just what you're looking for. A polished piece is not only cosmetically appealing, but in some cases it also enhances performance. Polishing is not only appealing because of its cosmetic and in some cases performance-enhancing properties -- it's also appealing because nearly anyone can do it for little investment.

Polishing can be done by anyone at any time anywhere. Anyone can polish nearly any surface with little experience and know-how. Polishing is basically made up of three things: knowing your surface material, knowing how much you should or can polish, and knowing your tools. If you know those three things, you can polish anything with a little guidance.

Now, first thing you must know is the surface you want to polish. Each metal has different polishing characteristics. Some metals can't be polished at all. Metals like pure iron and lead cannot be polished. The first thing you'll need to know is what type of material it is. Whether it's steel or aluminum or one of the other many times of pure metals and alloys found today. After you find out what type of material you're wanting to polish, you will need to find out what type of metal it is -- forged, billet, or cast. Each of these types of metals has different characteristics.

Forged metal is a metal that was basically compressed into its current shape. This process eliminates all the air pockets in the metal to create a more solid and sturdy piece. This type of metal can be polished thoroughly without the fear of polishing through a skin layer.

Castings are a metal that have been cast into a mold and let cool. This type of metal contains trapped air pockets beneath the "skin" layer. The meaning of a "skin" layer is that the casting developed a smooth thin skin-like layer over the material due to the smoothness of the casting mold. Now, this type of material's "skin" layer can be polished, but only a certain amount of material can be removed during the polishing process without polishing through the smooth "skin" to the air pockets in the casting below. This casting procedure is used in most manufacturing of OEM and aftermarket parts unless otherwise stated. It can be polished to a fine mirror-like quality, but use caution.

Billet material is a piece that was machined or carved from a single piece of material. It is the craze as of the past decade. While it is structurally inferior to forged pieces, it can be polished like forged pieces. Billet aluminum, however requires more steps for a good polish due to its ease of scratching and unwillingness to buff out once scratches develop.

Now that you know what type of material you're working with, you can figure out how much material can be removed during the polishing process for that particular type. You will need to look at the piece itself. What is the piece used for? Can you safely polish the part without ruining structural credibility? Can the part be polished and still perform its duty adequately? If so, continue on.

Now that you know your material and part, what tools do you use? Tools can range from basic sandpaper and elbow grease, to liquid or bar cutting abrasives (rouge) and cloth wheels or conical buffs used with your household drill, drill press, small rotary tool or an arbor. What you will most likely be using depends on the size of the piece to be polished.

There are a variety of companies that sell polishing supplies. Some offer kits, some don't. The rouges and cutting abrasives come in both waxy bars and pasty liquid form. Each of these has a different part to play in the polishing process. The pastes have grit values just like sandpaper. Actually, these pastes are sandpaper -- just in liquid paste form. The bars do not have grit value. They are color-coded -- black (harshest) to white (most gentle for final finishing). Different companies has different final finishing colors -- some finish with white, some with pink. Consult the company for further color-coded information before use. Also, each type of material has its own special abrasives. Each buff of wheel has its own place also. The tighter the weave, the harsher it will cut the surface. The looser, the closer you get to a finer polished finish.

Now I will demonstrate the steps to polishing a cast aluminum wheel.

1. Check to see if the part, in this case a cast wheel, has any clear coating. If it does, it must be removed with a chemical stripper before polishing.
   
   
2. Prepare your tool. In this case, an electric drill. Get the drill ready for use, start with a firm tight weave conical buff. Get the drill up to a low speed and apply the cutting (cut and color) abrasive to buff, then to the metal. This step is just basic smoothing and blending.
   
   
3. Next, with a new clean softer buff use a softer jeweler's rouge to clean up the scratches and blend the polished surface uniformly. Now the wheel has a basic polished look. If you want to go a step further, to mirrored finish, use another new clean open weave buff and an even finer polishing compound. Remember on each level to add more rouge every 20-30 seconds and try to keep the surface at a constant uniform temperature.
   
   
4. After the wheel is sufficiently polished to your liking, clean with a wax and grease remover and clear coat. You could also get the wheel clear powder coated.

You can do the same with hand rubbing with sand paper and liquid polish for smaller parts.