Chrome Pitting and Aluminum Spotting

So I bought a vintage trailer and now the fun begins! The first decision I have to make is whether to restore or replace the original hardware. I would like to restore, but all of the chrome is flaking off of the original pieces. I called the local chrome shop and they said the parts were too small and the bumper was too big to chrome (aka they only want to do wheels.) What are my alternatives? Has anyone use POR-15 with the Stirling Silver top coat?
Next, on the back of my trailer is a plate of what I thought was Aluminum.
It looked dull
So I tried polishing it with Morther Mag's Aluminum Polish
And these black marks showed up. They aren't the polish, I tried buffing, and washing, even scratching with my finger nail. The black marks are there for good.
So what did I do?? why do the marks show up after the polish, am I taking off a protective coat?
And finally, The paint on our trailer is stripping off with a simple soap and water wash. We decided the plain aluminum looks great. How long do we have before we need to put a protective coat of sharkhide or nuvite on? We're in Monterey and it's been raining more then usual, I don't want to watch a 50 year old trailer rust away in the backyard...
Thanks!!!!
Next, on the back of my trailer is a plate of what I thought was Aluminum.
It looked dull
So I tried polishing it with Morther Mag's Aluminum Polish
And these black marks showed up. They aren't the polish, I tried buffing, and washing, even scratching with my finger nail. The black marks are there for good.
So what did I do?? why do the marks show up after the polish, am I taking off a protective coat?
And finally, The paint on our trailer is stripping off with a simple soap and water wash. We decided the plain aluminum looks great. How long do we have before we need to put a protective coat of sharkhide or nuvite on? We're in Monterey and it's been raining more then usual, I don't want to watch a 50 year old trailer rust away in the backyard...
Thanks!!!!