Your basic school level, basic chemistry..
because it is an oxidation of the surface of Iron , steel is mostly Fe, (and O2 is rather needed for breathing) Fe+02 is 'rust'..

you are working on reducing it after the fact.. it comes thru chrome, and un painted steel ... so paint it oil it , and so forth
Try to not leave the bike in the rain, if it goes out, dry it off , bring it inside where its warm so the water dries.





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