How Does Dirt Damage the Finish?
As dirt builds up, it traps moisture. That moisture and dirt on the bottom layers are now in continual contact with the clear coat. As you drive down the freeway, the wind generated by your speed is enough to move that dirt around some, and as it moves, it makes tiny scratches in the clear coat. Over time, those tiny scratches become larger ones, and then the real trouble begins.
Once the clear coat is damaged, the dirt and moisture are able to seep underneath, and begin to lift and destroy the clear from underneath. Once the clear coat is gone, there is nothing to protect the paint, which is the next thing to begin to be abraded by the action of dirt and wind—and clueless, careless people brushing against the car in parking lots, or stupid kids writing stupid sayings in the built-up dust. All of these things continue to scratch the paint.
Once the paint is damaged, you’re down to the bare metal…and now the problems get worse. A scratch in the paint may be minor, but if it goes all the way through the paint, and exposes any metal at all, even if it’s too small to see with your naked eyes, that moisture and dirt now start working their devilment upon the metal.
Regular washing along with other routine maintenance helps retain your car’s resale value.
You’ve seen cars with “bubbled” areas in the paint around the doors or windows. Those are rust bubbles. As soon as the metal is exposed, the process of rusting begins, and it creeps under undamaged paint, causing those bubbles. It can start to happen as fast as overnight, especially if you live in a moist climate near a body of water. ** Salt water is the worst: it accelerates the damage exponentially.