My vehicle was looking trashed a few days ago (especially those avian creatures who use my car for their derivative Jackson Pollocks). So I decided to go all out and detail it myself. After a quick trip to the local car wash, I I followed up by hand claying, waxing, and polishing.
After finishing: Wow! It looked like it just came off the showroom floor. I’d not used a clay bar before and it really does enhance the look, along with making the cars pre-waxed surface as smooth as glass.
Alas, this is vanity! Today, the water will bead in nice, circular-to-elliptical patterns when it rains; in a few months, the water will smear like a smudge on the floor. And the birds will continue to use the vehicle as an unwilling canvass.
So what’s happening here? The wax, for all intents and purposes, doesn’t undergo any mechanical contact other than the fluid of rushing air as I drive in Search of the Real America®. (Note: no car covers were used to abrade away the wax.)
Is the wax itself sublimating away from the heat (re: the Sun), or perhaps the more volatile components?? Or is it photochemical reactions? Or is it chemical alteration from the environment? Or, all of the above?
And what hope for is there for a bottle or can of ACME Lifetime Car Wax used by Coyotes in Search of Roadrunners in the American Southwest™? Could such a thing exist, be reasonably priced, and wouldn’t require a Hazmat suit to apply?
I don’t know about the other causes, but: "the wax doesn’t undergo any mechanical contact other than the fluid of rushing air… and countless particles of dust and debris.
I’ll note that my car remains parked most of the time, as my bicycle serves as the primary means of transportation. In addition, most of my driving is at lower speeds (25 to 45 mph).
Where the wax loss occurs the most is not the front of the vehicle, but the top. That’s probably indicative of some action from the Sun, weather, and the accumulation of particulates. (As time passes, the beading effect lasts longer on the sides of the car than on the top.).
Have discovered tree sap is a nasty substance–it literally will attack the coating down to the paint altering the color. I’d have to sand it to the base layer and repaint it.
My particular nemesis was Quercus palustris (Pin Oak) which did quite a number to my rubber trim (bubbling of the neoprene).
If it is heavily oxidized, an application of rubbing compound will remove it. Lot of elbow grease, but put on some wax after and it should last a long time.
I think this was a reaction to the sap’s chemical makeup–not oxidation.
Previous to my detailing a couple of years ago, I tried rubbing compound to see if it would mitigate the marring. Once I detected the paint being removed, I carefully kept an eye on the marred surface to see any changes–there were none as I continued with rubbing the surface. So I stopped and waxed the spot.
As far as I know, carnauba wax degrades due to heat (its melting point is in the same range as that reached on metal surfaces of a car parked in the sun), and due to UV exposure (the UV light from the sun can break chemical bonds in the wax and accelerate oxidation reactions in the wax). Both these processes weaken the attachment of the wax to the paint and make it more susceptible to being removed, primarily by water exposure during rain or car washing. Chemicals in car wash soap as well as the mechanical action of washing and drying remove wax as well.
Of course, the presence of wax helps protect the paint from a lot of these processes, which is sort of the point.
If you put some wax on a car and then shut it in a climate-controlled garage for 10 years, it should still look pretty good. By the same token, if you kept the car in the garage and only drove it for a few hours at a time on dry days, the wax would last a lot longer.
There are now synthetic alternatives to carnauba wax that work a lot better and last a lot longer than conventional wax. These are often referred to as “polymer” waxes or sealants. The application process is basically the same. It has been a few years since I’ve had a car I cared about waxing, but when I did I used products made by Zaino (www.zainobros.com) with great success. I would usually get 8-12 months of water beading from a single application of their Z-2 sealant, despite leaving the car parked outside in the sun and rain most of the time.
Oh I forgot about nasties in the air. I don’t have access to an ozone generator any more, but it would be fun to dissolve some wax, subject it to ozonolysis, and analyze the products.
Well, yeah. The point of the question was looking for the specifics. One could Google for answers, but I find the SDMB tends to give a diversity of answers that are more satisfying. Fighting ignorance and all that.