Corrosion Properties of Different Highly Alloyed Clad Materials for Offshore Applications Manufactured by a New Thermo-Mechanical Rolling Process

A new thermo-mechanical rolling process for cladded steel sheets was developed and established. In particular five highly alloyed clad materials (PREN values from 26 to 52) were subjected to four different production routes with varying parameters (end rolling temperature and cooling rate). All rolling conditions (including two reference samples, which were solution and isothermally annealed) were investigated by means of Streicher-test according to ASTM G28A and an electrochemical method (DL-EPR-test). SEM characterization of all investigated material conditions was done after corrosion testing to determine the type of corrosive attack. Furthermore, pitting resistance was evaluated by measuring current density - potential curves in an artificial brine. A strong correlation between annual corrosion rates (examined by means of Streicher-test), EPR-test results, CPT and current density - potential curves was found. In conclusion, the most promising fabrication route regarding corrosion properties was evaluated for each material and compared with the reference conditions. It is shown that for each material at least one rolling condition exhibits equal corrosion performance like the solution annealed reference condition.