DrScientist

just noticed this stain in the paint on roof, near the sunroof seam.

i was rinsing salt and grime off the car yesterday when i first noticed it. it may have been like this as long as a week, but not more than 2 weeks.

it seems to be in the paint/clear coat, as any rubbing/washing seems to do nothing.

any ideas what it could be, and how to get rid of it quickly and most completely?

also, i keep my car in a nyc garage where cars are sometimes stacked... so i could it be something dripping from a car above?


thanks for the help.

TOGWT

Calcified Water Marks

Often found from parking in municipal or underground parking facilities, calcified water spots on paint and glass, water and concrete spots are pretty much the same chemically; they are consist of calcium (Ca) and magnesium (Mg) both of which are basic (alkaline pH 10) with the concrete being cross-linked with water

Correction
• These can usually be removed by using detailer's clay to remove any hardened surface deposits
a) Apply 1:1 ratio distilled water with distilled White Vinegar (Acetic acid) solution, and using a spray bottle, spray that mixture on the spots and let them "soak." Then rinse with water and repeat as necessary.
b) If the ambient temperature water/vinegar mix does not work, warm (100-120 degrees) 100% distilled White Vinegar, saturate a clean kitchen sponge with pure vinegar and hold the sponge over the concrete spots for a few minutes
c) If the above do not remove them try equal parts distilled water, isopropyl alcohol and distilled white vinegar. The acid in the vinegar will help etch and dissolve the concrete.
• Rinse the area thoroughly with water after the vinegar and then reapply wax or sealant to that area.
• To remove any surface etching use a machine polish ( Optimum Polish, Optimum Compound, Z-PC Fusion Dual Action Paint Cleaner or Klasse All-In-One (AIO) and a cutting (LC Orange or Yellow) foam pad (speed # 4-5.0 ) to level the surface (use the least aggressive polish/foam pad first, if this doesn’t remove the problem step-up to a more aggressive set-up)
• Work on a very small area at a time (2-foot x 2-foot) until the polish has run out
• Repeat this process two or three times, as necessary
• If none of the above methods remove the etched water spots consider wet-sanding the paint finish
• Reapply surface protection once spots have been removed

MoeMistry

From the rainbow "look" of the stain, it looks to be some sort of petroleum-based stain. It could very well be some oil from the car above. A simple polishing will do the trick. Then wax the area. I'd think twice about leaving the car in the open under another car. You should cover it. Hope this helps.

SteveG

I have what appears to be an indentical stain. It has that same rainbow effect and appears to have breached the clear coat. I used P21S cleaner; no joy.

Also the attendant at the garage apparently tried to wipe it off and left tiny swirl/scratch marks.

Will rubbing compound (gently applied) damage the clear coat?

I can get a picture, but it looks exactly like the one above. I believe the paint color is the same as well, slate grey metallic.