Development of an electrochemical depth profiling method to optimize the corrosion protection on aluminium cladded sheets for automotive heat exchangers

摘要

A better understanding of corrosion evolution in the different layers of aluminium brazing sheets used for automotive heat exchangers requires the knowledge of the local electrochemical potential through the material thickness. Such data is highly valuable to design future architectured sheets as there is a continuous demand for down-gauged and corrosion resistant materials. In this work, a methodology to establish the electrochemical depth profile by successive etching of cladded aluminium sheets is proposed. The protocol was based on a parametric study addressing the role of chloride concentration, acidity and solution aeration on the corrosion potential value as a function of immersion time. The methodology was applied to various three-layer sheets as well as a multilayer material. By considering both pre- and post-brazing conditions; Zn containing clad; Cu-containing and Cu-free core alloys as well as the addition of an interlayer, the importance of the different protection mechanisms was clarified.