For those of us who live in the Northeast or Midwest, no one has to explain corrosion. We have lived with automotive corrosion so long that it registers as specific words in our vocabulary, such as rust bucket or rusty beater.
IMAGE / AL THOMAS
Corrosion is caused by a combination of exposed metal, oxygen and electrolytes. Automobile manufacturers go to great lengths to protect and cover all metal during the manufacturing process. Still, there are many natural causes of corrosion, such as chips and scratches from normal-use road salt applied for winter safety, acid rain (especially in industrial manufacturing areas), polish and moisture of all types. Moisture and its ability to sneak into areas that are not directly exposed to rain or water when washing the vehicle can be difficult to deal with.
In winter when we get into a vehicle with snow on our boots, warm air melts the snow into the floor mat. The heat further evaporates it, allowing the moisture to float into areas where it otherwise would not go, such as inside the dashboard and other places that only vapor can reach.
Figure 1 (IMAGE / AL THOMAS )
We also expose metal to the normal repair process as we restore a car to its pre-accident condition. One of our goals when restoring corrosion protection to a vehicle is to completely coat any metal that may have been exposed during the repair process. Often it is quite obvious where our repairs have exposed steel during the repairs (Fig 1).
But other areas are sometimes overlooked, such as the areas of a pinch weld where the anchoring clamp has damaged the factory finish and even through to the corrosion protection, which was applied by the manufacturers (Fig 2).
Figure 2 (IMAGE / AL THOMAS )
Even more subtly, when the hammer and dolly method is used to repair steel corrosion repair underneath, either a pick hammer or a dolly (Fig 3) scars the backside of the steel being repaired, and a corrosive hot spot is made. All corrosive hot spots caused by the repair process must have their corrosion protection restored.
Figure 3 (IMAGE / AL THOMAS )
As technicians, we must be diligent with not only obvious corrosion protection restoration areas, but even the less evident ones (such as not damaging the vapor barrier between the door and the door trim panel). Or, we may fall short of restoring a vehicle to its pre-accident corrosion resistance.
Figure 4 (IMAGE / AL THOMAS )