A closer look at the internal corrosion test for automotive heat exchangers: the OY water test

Abstract

Nowadays, automotive heat exchangers are mainly made from aluminum. Over the last few decades, the development of aluminum brazing sheet has been mainly focused on the improvement of the external corrosion resistance. Recently, the interest of the heat exchanger manufacturers has also moved toward the assessment of the internal corrosion resistance. Accelerated tests are used to simulate in-service conditions. These tests are crucial as they provide information to predict the material and product performance. Various internal corrosion tests have been developed, the so-called 'OY water tests'. Among all companies, the testing parameters can be varied in terms of ion concentrations or pH. Although the OY water tests are constantly being improved, there is so far no common internal corrosion standard as existing for external corrosion assessment. The present work aims at providing better understanding corrosion mechanisms encountered in the OY water media. The role of various elements present in the solution, cupric, chloride, sulfate ions, has been determined. These parameters were assessed via immersion testing. In order to get better understanding of the corrosion mechanism, electrochemical analysis combined with SEM characterization was carried out. The electrochemical analysis enables the understanding of the thermodynamics and kinetics of the corrosion process while immersion tests are performed to quantify the level of corrosion and follow the surface evolution over time.