Development of advanced Al coating processes for future application as anti-corrosion and T-permeation barriers

Reduced ferritic-martensitic steels (e.g. Eurofer 97) are foreseen in future fusion technology as structural material in the HCLL concept, however, they show strong dissolution attack in Pb-15.7Li. Corrosion testing in Picolo loop revealed dramatically values of about 400 mu m/year at flow rates of 0.22 m/s at 550 degrees C. This large amount of corrosion products is transported and will be deposited as precipitates at cooler positions with the risk of line blockages as found in Picolo testing. Thus, reliable TBM function claims anti-corrosion barriers. Previous studies (e.g. Hot-Dip Aluminization) showed that Al-based coatings have such anti-corrosion and also T-permeation reduction behavior. However, industrially relevant coating technologies are missing and Hot-Dip cannot fulfill low activation criteria. Electro-chemical deposition promises such features, however water-based systems are unqualified. The investigation of Al coating methods from non-aqueous systems succeeded in deposition of Al-scales in high reproducible and controllable thickness from two different types of electrolytes. The first one is based on organic aromates as electrolyte and the second variant uses organic salt melts (ionic liquids). The specific characteristics and advantages will be discussed as well as the formation of the protective scales after heat treatment and their behavior in Pb-15.7Li. (C) 2010 Elsevier B.V. All rights reserved.