Credit: Brad Van Riper, Truck-Lite Co.

The best way to fight corrosion is to keep road salts away from copper wiring. These wires are not protected.


The green powder that we see as corrosion is not a coating. It was once wire, but the corroded portion no longer conducts.

Enough wire can be destroyed to turn 12-gauge wire into the equivalent of 18 — or even 22 — gauge. That increases resistance inside the wire, causing localized heating. Enough heat can be generated to soften common PVC (vinyl) insulation. Then, any rubbing from vibration can wipe away the insulation, causing short circuits and possibly a fire.

Never probe through insulation. Use the point of a continuity tester on metal terminals only. Moisture will entewr the pinprick and wick through the wire.


Since corrosion from road chemicals was first identified as a major problem in 2001, conventional wisdom had us pressure washing the undersides of tractors and trailers to remove corrosive salts. The American Trucking Association's Technology and Maintenance Council warns that pressure actually forces chemicals deeper into crevices. Instead, gently flood and brush the undercarriage to loosen and flush away salts.

— Paul Abelson ( is a former director of the Technology and Maintenance Council of the American Trucking Association, a board member of Truck Writers of North America, and active in the Society of Automotive Engineers.

Author's note: Thanks to Brad Van Riper, vice president of research and development and chief technical officer with Truck-Lite Co., for his help with this column. Van Riper is the 2009 recipient of the Technology and Maintenance Council's Silver Spark Plug award.