Characterizing Pitting Corrosion of 90/10 Cupro-Nickel Chiller Tubes

The in-service 90/10 cupro-nickel tubes in a water-chiller system suffered from severe corrosion damage during their relatively short service life causing unexpected down time. In addition to downtime, the environmental risk associated with losing refrigerant was also a concern that initiated this investigation, Microstructural investigation using SEM and electron microprobe indicated that pitting corrosion had resulted in local nickel depletion, During the corrosion process, copper appeared to have re-deposited around the corrosion pits accelerating the local corrosion.