Abstract
Cathodic protection with an external current was applied to prevent stress corrosion cracking (SCC) in a reactor vessel made of SUS 316L stainless steel containing an organic acid with 0.5%Cl-, pH 3 at 95°C. Transgranular SCC occurred mainly along the welded zone on the vessel wall after about 1 year operation without the protection. Initiation of the SCC was assisted with pitting and crevice corrosion caused by the deposition of an organic scale. A protection potential of -0.42V vs SCE and a required current density of about 10μA/cm2 were obtained by electrochemical measurements both in laboratory and field experiment. A magnetite and a pure zinc were used as the anode and the reference electrode, respectively. The SCC has been prevented successfully over 4.5 years after application of the catholic protection.
