ELECTROCHEMICAL INVESTIGATION OF ELECTROGALVANIZED STEEL PANELS EXPOSED TO AN ACCELERATED CORROSION ENVIRONMENT

Corrosion resistance is an important property requirement for materials applications in the manufacturing of automobiles. Zinc is widely used as coating of carbon steels, due to its anticorrosive properties. The most relevant application of zinc is zinc-galvanizing to protect steel from rusting acting as sacrificial anode. In the present study, the corrosion behavior of electrogalvanized steel panels by different thickness of zinc were studied under cyclic corrosion testing (CCT) and vehicle test. The CCT tests exposed the samples in a series of different environments in a repetitive cycle, these exposures consist of cycling between salt fog, dry and wet conditions. For the vehicle test, the steel panels were attached to the car exterior then exposed to corrosion and durability inputs with a variety of road surfaces for automotive testing and validation. Vehicle test is a large-scale laboratory test and is performed in facilities well designed by the automakers with the purpose of test complete vehicles and qualify them for real world application. The corrosion rate was investigated by electrochemical measurements such as open circuit voltage and potential dynamic polarization curves using the Tafel extrapolation method. The results suggests that the cyclic corrosion test has a more controlled corrosion environment, and the corrosion resistance is mainly related to the zinc thickness of the samples. The corrosion rate of the panels exposed to the vehicle test demonstrated that the position where the panels were attached to the car is the key factor to investigate their corrosion resistance.