Which Metals Can Be Polished to a Mirror Finish?
A metal polishing guide: which metals hold a mirror shine on their own, which need clear coat or chrome, and how to care for polished parts.
Polishing · · 4 min read · By San Marcos Powder Coating
Most metals can be polished to a bright shine, but only a few hold that shine on their own. In our shop, metal polishing works best on aluminum, stainless steel, magnesium and silver, which can stay bright without any coating. Steel, copper and brass polish up beautifully too, but they need a protective layer to keep that look: chrome plating for steel, and clear coat for copper and brass.
We have a simple saying at San Marcos Powder Coating: "If you can build it, we can polish it." The real question is what happens after the part leaves the buffing wheel. Below we walk through each metal, what the polishing process involves, and how to keep a polished part looking good.
Metals that hold a shine on their own
These are the metals we can polish and send home without a coating:
- Aluminum. Intake manifolds, valve covers, wheels, brackets and housings are some of the most common aluminum parts we polish. Aluminum takes a deep mirror finish and is a favorite for engine bays and wheels.
- Stainless steel. Stainless resists rust, so a polished stainless part keeps its shine with basic care. It is harder than aluminum, so it usually takes more work to bring up.
- Magnesium. Many older wheels and engine cases are magnesium. It polishes well and can hold its shine without coating.
- Silver. Antique silver boxes, trays and serving pieces polish to a bright, warm finish.
Uncoated metals do dull a little over time as they meet air, water and road grime. A light touch-up with a good metal polish usually brings them back.
Metals that need clear coat or plating
Some metals polish up well but will not stay bright without help.
Steel will rust if it is left bare. The best way to finish polished steel is chrome plating. The polished surface under the chrome is what gives chrome its mirror look, so the two go hand in hand. You can read more about the layers involved in our post on how chrome plating works.
Copper and brass look amazing freshly polished, then start to darken and tarnish in the air. We suggest a clear coat on polished copper and brass to lock in the color. This applies to solid brass and copper parts and also to brass or copper plating over another metal. Our post on brass, copper and nickel plating for home hardware covers those finishes in more detail.
What metal polishing involves
A mirror finish is built in stages. Depending on the part, the work can include:
- Sandblasting to strip old coatings, corrosion and grime.
- Grinding to remove pits, scratches, casting marks and weld lines.
- Polishing on the buffing wheel, moving through finer compounds to bring up the shine.
- Detail polishing by hand in tight spots, fins, lettering and trim that a wheel cannot reach.
- Clear coating for metals like copper and brass that need protection.
Prep is where most of the time goes. Any imperfection left in the metal will break up a mirror finish or show through chrome, so pits and scratches have to come out before the final buffing. Our post on why surface prep matters explains this in more depth.
Not every job needs a full mirror. We also offer satin, brushed, line graining and sandblasted finishes when a softer look fits the part better.
Custom pieces and production runs
We polish one-off parts for personal projects and also run production polishing for businesses that need a batch of matching parts. The shop got its start refinishing slot machines, and we still do production work for that trade today.
We see aero and naval parts, classic car trim, motorcycle covers, antiques and home decor. If it is metal and you want it to shine, send us a photo.
Combining polishing with other finishes
Because polishing, plating, powder coating and metal repair all happen under one roof, a single part can get more than one finish. A common example is a wheel with a powder-coated face and a polished lip. Another is a damaged trim piece that gets repaired, polished, then chrome plated. See our polishing services and chrome plating pages for more on how these fit together.
Caring for polished metal
A polished finish lasts longer with gentle care:
- Wash with mild soap and water and dry with a soft, clean cloth.
- Skip abrasive cleaners, scouring pads and harsh wheel cleaners, which can scratch or haze the surface.
- For uncoated aluminum, stainless, magnesium or silver, a quality metal polish now and then keeps the shine up.
- On clear-coated copper or brass, do not use metal polish. Treat the clear coat like a painted surface: mild soap, water and a soft cloth.
- Dry parts after washing so water spots do not etch or dull the finish.
Get a quote
Have a part you want polished? Call us at (760) 752-9825 or send photos through our quote form. We are at 1320 Grand Ave in San Marcos and work with customers across North County San Diego. You can also browse the gallery to see polished parts we have finished.
