Stress corrosion cracking of stainless steels recommended for building brine recirculation pumps

In earlier works, characterization and stress corrosion cracking (SCC) of casings of brine recirculation pumps, used in desalination plants, had been investigated. These casings which were manufactured from two types of Ni resist ductile irons have been reported to show different service lives. Material selection is believed to be one of possible factors to extend the service life of these pumps. Two types of stainless steels; UNS S31603 and UNS S32750 have been recommended as substitutes to Ni resist ductile irons. In this work, mechanical, metallurgical, electrochemical and SCC tests have been conducted on as received wrought samples made of these two types of stainless steels. Results have shown considerable higher yield and tensile strengths and corrosion resistance for the UNS S32750 over the UNS S31603. The latter steel samples have shown reproduced pitting behavior illustrated by electrochemical measurements and visual observations against no signs of pitting for UNS S32750 samples. SCC tests in hot brine environment have shown considerable less resistance to SCC for UNS S31603 samples as demonstrated by sample failures after few days of stress corrosion testing. No SCC was observed for UNS S32750 samples under the same testing conditions.