When rain falls it captures environmental pollutants from combustion exhaust. This causes the water to have a low pH (acidic). The sun heats and evaporates the water but leaves behind concentrated acid spots that cannot be removed. Prevention is key. Keep a good coat of wax on your paint and wash your vehicle at a professional car wash after it rains. 3 Minute Express Car Wash offers very high end Diamond Glow wax and Arizona’s only vehicle Sun Block in our exclusive Desert Shield wash package. This is the best value in Arizona for taking care of your paint!