[NoBones]

There is a detail product made by ZEP it is called
Brightner. It is a mild acid wash for Aluminum rims
on vehicles. It works great on stainless as well.
Find a carwash supply company in your area. It costs
about $22-$25 a gallon. I used to own an operate a self service carwash for 21 years in Daytona and the product will do what you want. The dilution ratio is real good. Just mix in a pump sprayer let it sit for about 2-3 minutes and just hose it off.
I use it any time stainless gets a little rust spot.
IE: Trim tabs, propeller, etc... It will work wonders
on your trailer. A gallon lasts me about 2 years...

Hope this helps, Ken