|MadSci Network: Engineering|
Allowing rust to form on the surface of Iron bearing metal will render the surface non-reactive. The rust (FeO2) will penetrate approximately 0.010" forming a barrier between the parent metal and the environment. This is why sunken ships are preserved for long periods of time. It is not recommended to use this process on moving parts since new surfaces will be exposed continuously. Unfortunately, I do not have the statistics on how extensive this process is used in the construction industry. Possibly another Mad Scientist may provide more information
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