Lap-joint corrosion of automotive coated materials in chloride media. Part 1 — Electrogalvanized steel

Lap-joint corrosion has been studied by several authors. However, the mechanisms involved in this type of corrosion, in the specific case of new painting substrates for the automotive industry, are not at all clear. The main purpose of this work is to study lap-joint corrosion in modern automotive painting substrates, namely electrogalvanized steel, galvanneal and electrogalvanized/galvanneal assemblies. In this first part of the work, electrogalvanized steel is studied using special specimens with spot-welded lap-joints, before and after salt-spray exposure. Special lap-joint spacements and positions were involved. The corrosion mechanisms proposed were based on the results obtained by visual observations, scanning electron microscopy (SEM) associated with X-ray energy dispersive spectrometry (EDS), X-ray diffraction (XRD), Auger spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).