Exhaust condensate - corrosivity of selected constituents on brazed aluminum

摘要

In the past, stainless steel was the material of choice for Exhaust Gas Recirculation Coolers in automotive and truck applications because of its high corrosion resistance in the exhaust gas environments. Now, Aluminum is being established more and more also as a suited material for such application in cases where only moderate corrosion or thermal stress is to be expected. Nevertheless, one of highest areas of concern is the corrosion resistance of the Aluminum materials in acid exhaust gas condensates. The paper presents results which help to get a better understanding of the corrosivity of typical well known constituents on brazed Aluminum. Focus of the experiments and their analysis is the influence of Chloride, Nitrate and Sulfate (at a constant pH value) on corrosion behavior of the samples. The influence of flux coming from brazing process will not be considered. An experimental matrix for constant immersion tests of brazed samples was created using a statistical approach with "Design of Experiment". Particularly, different amounts of the mentioned Anions could be investigated by a minimized number of tests. The evaluation of the test results (analysis by chemical and metallographic methods) was done by means of statistical regression methods. Finally, the influence of individual Anions or their combinations on corrosion properties of brazed Aluminum could be categorized as "significant" or "insignificant" and quantified in mathematical models.