For lots of people like me, when winter weather slams the door on riding fun, we get our motorcycle joy in the garage, working on a winter project.
One of the most fun and satisfying parts of building a bike over the winter is making all the raw parts beautiful. Sending items out for final finishes means I'm getting close to kicking a new bike to life. Whether I make, modify, or buy parts on the cheap, I usually refinish them to improve the appearance. You may also want to refinish a part to repair crash damage or just because you want a new look!
There are a variety of finishes, and some processes have an air of mystery about them, but narrowing the options to find the right finish to provide beauty and protection usually isn’t too hard. Hopefully, this brief primer will help clarify which problems different coatings solve.
Patina is the easiest finish to obtain. Generally, motorcycle wear is acquired simply by doing little or nothing. Paint cracks and fades, aluminum tarnishes, and steel rusts.
Generally, all it takes to develop this type of finish is time. There are some shortcuts, like tarnishing brass with ammonia or using saline solutions to speed rust along, but those can look faked. Some might posit that general wear isn’t a real finish, as it typically is not very protective. But the oxide that aluminum naturally forms, for example, is actually very protective for the base metal.
Why would you want this finish? In many cases, an antique motorcycle is worth more with a natural patina than if it has been restored to look as good as (or better than) when it first rolled out of the factory. On the other end of the spectrum, it would be hard to imagine a rat bike with any other finish, wouldn’t it?
Arguably the finish with the greatest variety in terms of appearance, everybody knows paint. It is a very thin finish (about five mils), sprayed on in liquid form, and requires excellent and painstaking surface preparation. It offers good protection from the elements and chemicals if a high-quality paint is chosen and applied correctly, but paint is also relatively delicate.
Paint is often chosen for applications where the need for beauty trumps the need for protection, because it’s available in a myriad of colors, gloss levels, and textures. Painted finishes can be manipulated through additives (pearl or flake, for example) or processes (lace or smoke) for even greater variety. Due to its delicate nature, it’s typically reserved for fenders and tanks, but there are exceptions. Heavy, thick paint is used on many frames, and drivetrain components can look wonderful when painted with a thick, high-temp paint that offers a textured look (“wrinkle” is very common).
Powder is a coating that is quite thick, relative to paint, and offers a similar look that is much more protective. Powder is applied much differently. Typically, a powder composed of fine polymer solids that has been electrostatically charged is applied to metal parts and then cured around 400 degrees for 10 minutes or so. Because of that temperature, use of powder coat is normally relegated to metals, but low-temperature powders do exist.
Because of the lack of liquid, powder coat is typically quite thick — up to 10 mils. This thickness can hide surface detail. That can be a problem, if you want to highlight a machined surface, or helpful, if you want to cover tooling marks or less-than-perfect prep work.
Powder coating is very tough when cured and resists both impacts and friction. That makes it good for protecting exposed metal parts such as frames, fork legs and chain guards.
Anodizing is an electrolytic process that produces a thicker, more uniform oxide on a part than the naturally existing layer. Anodizing is very thin. The most common type of anodizing used for motorcycle parts has a maximum thickness of just a single mil. It can take dye very well, which makes it possible to have a colored finish that appears translucent. Ano is seen almost exclusively in the motorcycle world on aluminum parts. The finish is fairly delicate, so it’s best suited for areas of the bike that will likely see little impact or friction.
It could be said that chrome is motorcycles. Chrome is laid down by polishing metal, then applying other reflective metals to it in sequence, such that each layer “likes” the layers that sandwich it, chemically speaking. It is a very durable finish if kept clean and dry. Metal parts are usually suitable for chroming, especially steel and aluminum. The process is labor-intensive, because the base metal must be polished to a mirror shine before the chroming process can begin. The cost to chrome items has risen steeply over the years due to the nasty impact the chroming process levies upon Mother Nature.
Ceramic coating is a type of thermal barrier used to finish parts. Traditionally, it has been used to retain heat within a metal part. The coating is somewhere between two and four mils thick, and usually has a matte appearance. In the motorcycle world, ceramic coating is used almost exclusively on exhausts. Retaining the heat in the exhaust moves gases through the pipe faster. It’s a good option for those who want to rescue a set of pipes that might not look so great any more, or for those who want a finished look on a set that was handbuilt.
Polishing is the act of making a surface bright and shiny. Uniform, bright appearances are created on metal by knocking down the microscopic “mountains” that exist on the surface of the piece being polished to the same level as the “valleys” that also exist. Polished parts typically can be repaired easily. If the finish is marred, it can usually be repaired locally and blended back in with the undamaged surfaces surrounding it. Because there is nothing to remove or apply, this finish can be changed with relative ease. Due to a motorcycle’s outdoor existence, a polished surface really only makes sense on metals that are fairly resistant to corrosion. Most polished parts in the motorcycle world are typically stainless steel or aluminum.
Other more esoteric processes, such as Parkerizing, cadmium plating, and nickel plating have been used over the years, too. Those are typically put to use in very specific scenarios and are less common.
Ultimately, success comes down to choosing the right coating that provides the combination of appearance and protection a specific part needs. Second to hearing a winter project fire up for the first time, no part of the process is more fun than making it beautiful.