Bleeding from small plastic coated Tarp on Polished surface

[brodjeaw]

While installing a rockguard on the front window in the blazing sun I put up a canvas plastic shade which worked until the rains came. I left it overnite in the down position covering the front window. The next morning I uncovered noticing the shadows resulting just over the Airstream Nameplate and some of the surrounding areas.
Anyone had any experience regarding this shadowing result. It does not have a caked effect but has discolored the polished surface. Any ideas???

[perryg114]

The wet canvas held water against the skin and accelerated corrosion/oxidation. Just touching bare aluminum with your hands can darken it.

If you keep a coat of wax/sealer on the polished stuff, it will help reduce oxidation.

Perry

[dwightdi]

The plastic coating on the canvas might have been flexible PVC. It loses plasticizer and its acidic nature might oxidize the surface of the aluminum. It will require a little repolish to remove it.