I think we have the same trailer cap and problem. Mine is a 2014 Laredo 320tg.
I think you are chasing a bigger problem. It is not really oxidation, it is failing. I had to re clear coat the top of the cap last year due to the water based clear coat pealing off. Think early 90's hoods on car with the clear coat pealing off.
This is what mine looked like after washing.
I called Keystone customer service after I had it re clear coated looking for new decals last fall. The woman stated that even though I'm the second owner, the decals could be covered under warranty. I never fallowed up on this. As they needed my Vin number and pictures of the issue. I only had the attached picture.
With talking with various RV dealers around me, this is a semi common problem with camper that sit for long periods of time. The cupboards need to be open above the bed to dissipate the heat that builds up and cause the clear coat to fail.
Seeing mine is fixed, I am currently looking for vents that I can add to cupboards to make sure this does not happen again.