Bonded contamination is a mixture of ferrous deposits such as brake dust and metal filings from railway tracks.
To remove this you can use a clay bar or in these pictures fallout remover.
The fallout remover is sprayed on and instantly reacts with the ferrous compounds, reducing them to a water soluble complex which can be easily washed away .
As you can see in the pictures the reaction makes the paintwork turn purple as the solution does its work.
The benefits of using this your paintwork is it keeps your paint work smooth and cleaner and mainly stops these metal particles from bonding to your paintwork causing irreversible damage .