engleski

Stainless Steel Crevice Corrosion Assessed in the Flowing System

The tendency of four types of stainless steel, austenitic UNS S31600, UNS S31254, and two duplex steels SAF 2205, UNS S32205 and SAF 2507, UNS S32750 toward initiation and propagation of crevice corrosion has been investigated in the flowing system of natural sea water in the Adriatic sea, at the location in Dubrovnik, Croatia. A new crevice corrosion testing method, developed by the Working Party on Marine Corrosion of The European Federation of Corrosion has been applied to assess crevice corrosion behaviour of stainless steel. Metal specimens mounted with crevice formers have been used for the monitoring the free corrosion potential in sea water during six months. At the same time the temperature, salinity, redox potential, the oxygen content changes, and the presence of bio film on themetal surface were detected. Particular attention has been payed to the mounting of plastic crevice formers in order to eliminate any corrosion process besides that one under the creviceformers, wich were held with washers, bolts and nuts of titanium. Sharp drop of the corrosion potential was used as an indicator of crevice corrosion initiation. As expected, the initiation and propagation phenomena were found to differ due to the type of stainless steel. After exposure in the seawater crevice formers were removed for visual and microscopic inspection of the crevic area on the specimen, and the weight loss measurement. Obtained results will serve in a Round Robin test on crevice corrosion performed by severalLaboratories of the Working Party on Marine Corrosion.

stainless steel; crevice corrosion; flowing system; seawater

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