Corrosion resistance of steel depends largely on the quality of the steel itself. When I was in the construction industry (now re-tyred) the highest quality steel was used in - for example - steel sheet piles in marine works. The life expectancy was measured in decades, in a salt water environment, with minimal coating. Another steel grade used for some items on motorway work, was Corten grade steel. No coatings were required, the steel took on a surface rust and no further corrosion took place. A bit like cast iron manhole covers. Lower grade steels, with relatively high content of impurities, starts to corrode from within. Protective coatings are not much help in such circumstances. So a galvanised chassis should last for ever if it is made from quality steel, and have a shorter life if it is made from a lower grade steel.
Would any one manufacturer outlast another, taking into account use, conditions, etc of the vehicle it is fitted to?
