Electrochemical protection of Zr against SCC by oxidizing HCL solutions

Results are reported for electrochemical protection of zirconium in HCl containing 500 ppm ferric ion. Corrosion rate and pit propagation rate data as a function of acid concentration (10-37%) and temperature (25-1070C) are first presented as a basis for observations of SCC and/or intergranular attack (associated with weld metals). U-bend, C-ring and sustained load tensile, and slow strain rate tests were used and compared to define conditions where SCC occurs. Along with electrochemical protection, heat treatment and reducing the ferric ion concentration are presented as ways to alleviate local attacks. Metallography was used to both define the mode of attack and show the benefits of protection techniques