Returning with a Wet Car

[Colin Morgan]

Had a quick look at conditions considered necessary for rusting - temperature/relative humidity.  The benchmark seems to be to keep below 50% humidity at 20 degrees C for slowed corrosion.  At lower temperatures, the humidity can rise higher before the corrosion increases, so a cold garage helps.  For any temperature, the corrosion rate rises ever more steeply as the humidity approaches 100%.  

Interesting that the level of air polution affects corrosion rates - dirty air means more ions in the moisture making it a better electrolyte.  Also that a 'dry' surface (no rain or condensation) is not sufficient to prevent corrosion - high humidity air is enough.

Colin