What would you do?

[m3f_NolliM3]

When I had taken the door panel off (passenger side), the vapor barrier was all crumpled up at the bottom of the door and when I straighten it out, I noticed the rust line. Apparently, the PO or their mechanic didn't seal the barrier properly and water had been sitting whenever it rains.



My thought is to just lightly sand the surface then spray some rust protection...since it's behind the door panel, there's no need to paint. What would you do?

[m3f_betrezra]

There is a rust eating spray and prep coating avail in spray can or a jelly.



I've used this for my battery tray with worse corrosion....... with good results.



You can sand 1st, then primer and rattle can paint that IMHO..... or just apply the rust eating spray/jelly. GL .

[m3f_abcurran]

Remove the existing barrier and butyl at/near the rust line. clean as much butyl away. mask off the area and sand the rusted portion trying to remove as much as you can. 80, 150, 220 grit. After sanding, get some phosphoric acid or zinc phosphate and liberally coat the sanded area and keep wet for 15 min. You'll be done when the metal appears "ashy." after that, wipe the panel with clean rag and you're ready for primer/rust inhibitor/sealer, really whatever product you want to put on.

[m3f_NolliM3]

There is a rust eating spray and prep coating avail in spray can or a jelly.



I've used this for my battery tray with worse corrosion....... with good results.



You can sand 1st, then primer and rattle can paint that IMHO..... or just apply the rust eating spray/jelly. GL .

Remove the existing barrier and butyl at/near the rust line. clean as much butyl away. mask off the area and sand the rusted portion trying to remove as much as you can. 80, 150, 220 grit. After sanding, get some phosphoric acid or zinc phosphate and liberally coat the sanded area and keep wet for 15 min. You'll be done when the metal appears "ashy." after that, wipe the panel with clean rag and you're ready for primer/rust inhibitor/sealer, really whatever product you want to put on.