Ah ha! contamination from a grinder? Mystery solved: when I bought the van in August, there were no rust specs on the roof. Now there are many.... all in the immediate area of the roof vent that was installed in October.
As for dealing with the rain gutter, I just stopped by AutoZone, and the fellow there suggested the following:
- sand with 3000 paper to knock off loose rust bits, wipe with a damp rag, and let dry.[/*:m:3dr5xisq]
- use a touch-up pen, which contains primer+paint. (Or should I use primer and paint separately as Philip suggested?) Let dry.[/*:m:3dr5xisq]
- spray with water, and lightly sand with 3000. Wipe down, and let dry.[/*:m:3dr5xisq]
- cover up with a clear-coat touch-up pen.[/*:m:3dr5xisq]
Does this sound about right? Is the clear-coat overkill?
Later this spring, I'll install my rain-gutter mounted Yakima towers, which will probably ride up there forever. A side-loading Thule Evolution cargo box will go up there, and eventually a kayak
. So, I suspect that maintaining the rain gutters will be an on-going task.