Wheel Assassin Iron Remover Gal
Small particles of ferrous-based ("iron") land on vehicles constantly. It comes from industrial applications, and largely from brakes on cars as they grind down. As it settles on the car (paint, glass, plastics) it can become bonded - especially if it gets wet from morning dew or rain, and then rust and bond to the surface. Normal washing will not remove this material.
Over time this will literally change the color of the car - making it appear slightly more dirty and less glossy. Furthermore, it will reduce the ability of waxes, sealants or coatings to properly bond to their intended surfaces, reducing their effectiveness.
The other obvious effect is that it will make the surface not feel smooth.
While clay bars can use mechanical force to sheer off some of the material, sometimes it is embedded below the surface and clay cannot remove it - this is where chemical decontamination comes into play. A chemical can dissolve this material under the surface where clay cannot reach - allowing for a more complete, cleaner removal.
If contamination is severe, it is wise to use chemical treatment before clay to significantly reduce the amount of effort and aggressiveness needed from the clay medium to remove the material.