I had to remove my fuel tank due to rocks and dirt in it... Drained the old nasty gas out and rinsed it out... In looking inside the tank I noticed it flash rusted in some areas but not in others... What can be done to stop the flash rusting?

I am doing this at home so whatever process it be done needs to be non toxic...

1954 Chevy 3104 3 Window Hydra-Matic in my family for over 60 Years

Once in a while you get shown the light in the strangest of places if you look at it right... "Scarlet Begonias" Grateful Dead 1974