Car body paint is usually applied in several coats; electrocoat, primer, base coat and clear. It is also baked at 150C for half an hour. The plastic components are painted elsewhere and applied in three coats; primer, basecoat and 2 pack clear then baked at 80C for half an hour. The electrocoat has had the biggest effect on corrosion resistance, the switch to clear over base has improved the appearance (colour and gloss retention).I've never used it. But when I look at (say), a car that is ten years old and the paint is still perfect given minus 10 degrees to plus 30 degrees, together with all the flex a car can go through - one has to wonder why, for example, "paint for external metal" (i.e. railings) can only last "up to" five years.