Moisture
Wet sand and dirt deposits that accumulate on the underbody and in the body cavities accelerate corrosion. Floor mats, in which moisture gradually accumulates, cannot dry completely inside the car and must be periodically removed to dry.
High humidity
Car body corrosion accelerates with high air humidity, especially if the humidity is combined with constant positive air temperatures, significant air pollution and regular use of salt compounds for road treatment.
Air temperature
As the air temperature rises, the rate of corrosion increases, especially in poorly ventilated areas of the body. Corrosion processes accelerate in regions where the air temperature remains constantly above zero.
[Data copied from web resource nissanbook.ru]
Air Pollution
Industrial air pollution and high salt content (on sea coasts or with intensive use of salt compounds to combat ice) accelerate corrosion processes. Road salt also accelerates the destruction of paintwork.