Corrosion barriers processed by Al electroplating and their resistance against flowing Pb–15.7Li

Abstract

In the HCLL blanket design, ferritic–martensitic steels are in direct contact with the flowing liquid breeder Pb–15.7Li and have to withstand severe corrosion attack. Beyond corrosion, T-permeation from the breeder into the RAFM-steels is also an important issue and has to be reduced significantly. Earlier work showed that Al-based coatings can act as barriers for both, however, applied processes e.g. HDA or VPS exhibited strong drawbacks in the past. Meanwhile new industrial relevant coating processes, using electroplating technology are under development and called ECA (electrochemical aluminization) and ECX (electrochemical deposition from ionic liquids) process. In this study electrochemically Al-coated and heat-treated Eurofer samples were tested in PICOLO loop for exposure times up to 12,000h (ECA) and 2000h (first results ECX) respectively to determine corrosion properties in flowing Pb–15.7Li (550°C, 0.1m/s). Cross section analysis afterward corrosion testing proved the ability of thin Al-based barriers made by electrochemical techniques to protect the bare Eurofer from corrosion attack even at exposure times of 12,000h. Determined radial corrosion rates lay between 10 and 20μm/a. First results for ECX coated samples (2000h) revealed more homogeneous corrosion behavior of the barrier layer itself compared to ECA.