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Careful design of body panels and joints is the best starting point for corrosion prevention. Prevention of oxidation or corrosion of steel auto body panels requires prevention of contact between the oxygen-rich environment (air) and metal.

Road salt usage, use of hygroscopic calcium chloride and general environment sources, coupled with often marginal vehicle cleaning and maintenance, cause corrosion cells to accumulate and thrive,

Building lighter, smaller, more fuel-efficient cars has resulted in reduced steel gauge and reduced percentage of corrosion tolerance. Dips, sprays, and different coatings are among the methods for preventing contact between hostile environmental elements and metal.

Hood

For corrosion resistance, the following items should be considered by the designer: all essentially horizontal inner panel surfaces should be sloped toward a drain hole, drain holes should be located at low points of all areas which trap fluid. In the hood latch region a flat area is generally needed for the latch mechanism and should be checked for proper drainage.

Fender

Fender assemblies generally have three major components: fender outer panel, fender rear reinforcement or fender inner panel. Splash shields and aprons often serve to protect fender, dash panel, lamp housings and wiring from stone abrasion and wheel splash as well as being structural panels.

To improve corrosion resistance reinforcement and fender are preferably separated to a maximum allowable distance. Attachment of rear reinforcement to fender at their lower contact should be a minimum 15 degrees angle to provide proper drainage. Large openings around headlamps are preferably avoided or shielded to prevent erosion corrosion (this is accelerated corrosion of a metal surface due to movement of a corrosive fluid over its surface; in this case the fluid is hot humid salty air).

Doors

Sheet metal panels of a door assembly consist basically of a door outer panel, door inner panel, hinge reinforcement, and a side impact or intrusion bar. A completed door assembly with glass, weather strips, water shields, and trim panels installed presents a most unfavorable problem for a corrosion protection engineer. Water, road salt, and dirt will enter the door, but its basically sealed-off condition and lack of air circulation creates an undesirable humidity chamber.

This effect can be minimized by the following: all horizontal areas should be sloped a minimum of 10 degrees toward drain holes, drain holes at the door bottom should be at its lowest point.