Corrosion resistance of Al-based coatings in flowing Pb-15.7Li produced by aluminum electrodeposition from ionic liquids

Reduced activation ferritic-martensitic steels are intended to serve as structural materials in different blanket designs, e.g. HCLL, DCLL and WCLL. In these designs the material is supposed to be in direct contact with the flowing liquid breeder material Pb-15.7Li at an operating temperature of up to 550 °C. These conditions will lead to severe corrosion attack of the steel and high corrosion rates of up to 400 µm per year are reported in the literature. To avoid or reduce corrosion Al-based corrosion barriers were developed in the last years by using electrochemical techniques to deposit aluminum. Until now two processes have been developed. The first one, so called ECA process, is based on volatile toluene electrolytes. Long-term corrosion experiments on these coatings indicated reduced corrosion rates compared to bare Eurofer steel in flowing Pb-15.7Li. However, these Fe-Al scales showed inhomogeneous corrosion attack of the corrosion barrier itself. In this study the improved ECX process was applied to produce Al-based coatings. The short-term corrosion behavior of such barrier coatings was analyzed for up to 4000 h by diameter measurements and metallographic examinations. The investigation revealed uniform corrosion in comparison to inhomogeneous attack in case of ECA coated samples and reduced corrosion rates of around 20 µm/a even for low exposure times of 4000 h.