[TOGWT]

Originally Posted by droptop335

Other than the car sitting in a metal or body shop, why and how on earth would iron shavings get embedded into your paint?

Rail Dust [: (ferrous oxide FeO) from the day a new car is shipped its surface is under attack. The railcar its sitting is showered with airborne metal particles from the rails. These ferrous metal particles embed themselves into the paint and will eventually oxidize and form rust corrosion under the clear coat]

Brake Dust [: sintered ferrous oxide FeO) particles from your own and passing vehicles will also get embedded in your paint.]

Brake pads are manufactured from a range of materials including Kevlar fibres, Mono carbon fibres; Polymer based adhesives and metal particulates from both the pads and brake rotors (ferrous oxide FeO); all of which must factor into the cleaning process. The brake pads polymer adhesive residue can actually turn acidic, etching and pitting the wheel finish.

Automotive paint systems are porous; when you add water and heat to an acidic substance it will erode the paint system very quickly (the heat opens microscopic fissures in the clear coat allowing ingress, the water provides a carrier system for the acid, and heat acts as a catalyst each time water is reintroduced the acid will be reactivated). The paint surface should be periodically neutralized / decontaminated, i.e. once every two years (See also Reactivity)

The only way to completely remove sintered (heat fused) ferrous iron particles is with a dedicated decontamination system that opens up the paint's pores to release iron particles and to neutralize the caustic compounds that have developed as a result of the particle. In one step, you can eliminate both the cause and its effects.