The electrochemical action of stainless steel trim in direct electrical contact with auto body steel can promote accelerated rusting of body steel in crevices where paint may be defective or damaged. Rain, snow, and/or road splash containing deicing salts and other contaminants provide the electrolyte. A dissimilar metal battery is created under such conditions resulting in the less noble body steel undergoing rapid galvanic attack.
Attempts to prevent this type of corrosion have been investigated in the laboratory and by actual service testing. The various methods evaluated included electrical insulation to interrupt the flow of galvanic currents and the use of a third sacrificial metal which would provide cathodic protection. Among the many third metal systems tested, the aluminum striping concept was proved to be the most practical as well as the most effective for suppressing objectionable galvanic rust of autobody steel.
In principle, the aluminum striping development involves a technique to bond continuous stripes of aluminum to production-width coils of finished automotive grade, stainless steel strip. The aluminum stripes can be positioned on the stainless steel strip at preselected locations, which ultimately places them on the exterior surface of the return flange (car body contacting surface) of fabricated trim sections. In service, the ideally located stripes of aluminum provide a highly effective system which protects against galvanic attack.
The effectiveness of the aluminum striped product in combating galvanic corrosion has been established by service testing for a number of consecutive winter seasons in the Pittsburgh area and on one of a fleet of test cars which has now been in service in the Detroit area since the fall of 1969. Galvanic corrosion test assemblies have also been exposed on stationary racks along the seacoast in Miami Beach, Fla., and Kure Beach, North Carolina.