Does waxing your car have a long-term beneficial effect on the paint-work?

Question

Everyone, especially people who love washing and waxing their cars, has been telling me about the long-term benefits of regular waxing. They tell me that the layer of wax acts as a protective shell and will prevent contamination (such as UV radiation, bird droppings, tar, etc) from "burning" into the car's paint. As a consequence the car's paint would keep it's good looks longer, and ultimately the car would even have a higher resale value.

I find that hard to believe. I don't know anything about chemistry so probably my thinking is not making sense at all, but the way I see it is that car waxes contain a number of natural and less natural ingredients but basically I think every car wax is in fact just grease. So you put a layer of grease on you car, which indeed makes it shine more and causes water to not stick as much to the paint. But I have a hard time believing that this thin layer of grease is going to cause any long-term beneficial effect. I bet if you wash the car regularly, that after 5 times the wax is simply gone and even if it does stay on the car, can this really have a significant protective effect? If yes, I would like to understand how.

The problem I have is that everyone who is telling about the benefits only refers to personal experience. Is there any real scientific and independent test result that proves these claims?

Answer 1

Partial answer only.

Wax doesn't protect the car from acidic rain:

Does wax protect from acid precipitation: Waxed automotive finishes in the Acid Dew and Fog Test, SCHULZ U.; ZWICK W., European Coatings Journal 1997, no9, pp. 784-790

Tests with seven different wax recipes and two current types of coating showed that wax on coating surfaces is not a barrier against acid atmospheric precipitation. Waxing can both slightly inhibit and enormously increase the harmful effect of aggressive precipitation on the coating.

Answer 2

Car paint is a very mature industry. There is two main ways a color coat can suffer: the color can change, e.g. bleach, and the surface can erode. An eroding surface optically adds white to the color beneath by adding diffuse reflection (think about a glossy CD-cover that has a black booklet underneath - if the cover is scratched the booklet will appear greyish, not fully black anymore) - this does not mean that the actual coloring agent is bleached, modern cars colors don't do that anymore, generally, it is just the color plus the diffuse reflection of the eroded surface of the covering, clear, layer. Buffing up that surface with wax will 'make the colors more vibrant' by reducing the diffuse reflection (changing it to specular reflection, i.e. mirror-shine). The wax does not actually do anything to the pigments themselves.

To really ruin the color, the erosion would have to progress all through the clear coat, to the color layer itself. Neither is that realistic, nor is the wax going to be much hindrance, if the environment really is that bad.

As wax does not hinder the influence of vapors, the only big effect to stop would be photooxidation/-degradation of the coating. As the coating is ideally very thin, on the order of nanometers the absorption of UV would have to be phenomenal to make a dent in the incoming radiation. The clear coat with its many micrometers of thickness would be a much more appropriate venue for anti-UV measures. It would need to reflect, so a UV-spectrum photo of a half-waxed car woul be the clincher.

EDIT: I found an interesting video on YT (results at 11:30) where a garage owner does some testing of clear-coat/sunscreen/various waxes and 'ceramics' regarding the UV-protection they offer. The amount of thought he put into his test setup is heartwarming, though he does not, for instance, control for thickness - result: Clear-coat does serious UV protection, waxes do not.