Bison calls this shiney aluminum "Brite-Dip" .... It looks simular to a polished surface, but then again it looks like a plated surface... I would contact Bison and talk to someone in the engineering department. Use the wrong cleaner and you may have a permanently etched surface.

Brite Dip Metal on Exterior Sides (Full or Partial)

http://www.bisontrailer.com/contact-bison.html

I don't believe the aluminum on your trailer is anodized. It's an expensive and time consuming process, and won't produce the high gloss found in most coatings. In the past, I've heard of the finish on a Bison being ruined, when the owner had the trailer acid washed. The acid ate through some of the coating, exposing the aluminum to air, which resulted in oxidation, discolouration etc etc. This would not have happened if the finish were anodized.

Bison, as does most builders, buys their aluminum precoated in sheets or rolls. The coatings can be urethane, polyester, acyrlic or epoxy. Some of the epoxies can be microscopcially thin and invisible to the eye. Most of the finishes are only a few millimeters thick and are oven cured at about 700 deg F. Many manufacturers purchase their products based on price, and if a sales person says I have this lot for such and such at a good price, the business will buy it, while not knowing all the particulars. It will also mean that a trailer built at a different time period, can be constructed of different materials.

All the finishes I mentioned, can be cleaned and waxed without being damaged. There are literally dozens of products you can use in this effort. Streakmaster and Metal Wax are predominately known within this forum. Many marine, aircraft and automotive products work equally as well. Any mild cleaning "polish" with a wax additive will clean and protect the finish. Do not use any aggressive rubbing compounds, or harsh chemicals to clean your trailer, including acid washings. Generally, any product that you can use on the clear coat finish of an automobile, can be used on your trailer.

I like products used in marine applications. They generally are durable, not easily degraded by UV exposure and work well in a most hostile environment. A month on the water would equal several years, of a trailer's normal exposure to environmental hazzards. A product made for fiberglass (polyester) and metal, will work well on coatings of every type. The final finishes have to be very durable for UV protection, a salt water environment and the constant abrasion of water and weather. The same holds true for aircraft products, if you are close to a FBO.

Here are some products for your consideration:

http://www.jamestowndistributors.com/userportal/search_subCategory.do?categoryName=Marine Cleaners&category=587&refine=1&page=GRID

If you can't highlite the whole link, click on "cleaners" supplies from the master list.

BOL      Gard