Cathodic protection

Cathodic protection (CP) is a technique to control the corrosion of a metal surface by making that surface the cathode of an electrochemical cell.

Galvanised Steel

Most modern cars have galvanized (zinc-coated) steel frames and panels. Unprotected steel forms a layer of iron oxide, which is permeable to air and water and allows corrosion to continue underneath. However, zinc oxide (produced on the surface of zinc-protected objects) is impermeable. As long as the zinc and zinc oxide layers are undisturbed (i.e. not scraped or sanded off), the steel underneath will not rust.

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Galvanised steel has some self repairing properties; small scratches where the steel becomes exposed will be recovered by the zinc. The happens because the zinc from the surrounding area will dissolve and be deposited on the steel, replacing what was lost to the scratch.

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