Subaru Legacy Owners Manual: Most common causes of corrosion

The most common causes of corrosion are:

•  The accumulation of moisture retaining dirt and debris in body panel sections, cavities, and other areas.
•  Damage to paint and other protective coatings caused by gravel and stone chips or minor accidents.

Corrosion is accelerated on the vehicle when:

•  It is exposed to road salt or dust control chemicals, or used in coastal areas where there is more salt in the air, or in areas where there is considerable industrial pollution.
•  It is driven in areas of high humidity, especially when temperatures range just above freezing.
•  Dampness in certain parts of the vehicle remains for a long time, even though other parts of the vehicle may be dry.
•  High temperatures will cause corrosion to parts of the vehicle which cannot dry quickly due to lack of proper ventilation.