51312-01070-SCC and Crevice corrosion inhibition of Steam Turbine ASTM A470 Steel and 7050-T74 Al-alloys using V

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Product Number: 51312-01070-SG

ISBN: 01070 2012 CP

Author: Bezad Bavarian

Publication Date: 2012

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The accumulation of damage due to localized corrosion pitting stress corrosion cracking and corrosion fatigue in low pressure steam turbines components such as blades discs and rotors has been consistently identified as being among the main causes of turbine failure. Accordingly the development of effective localized corrosion inhibitors is essential for the successful avoidance of unscheduled downtime in steam turbines or other complex industrial and infrastructural systems and for the successful implementation of life extension strategies. Stress corrosion cracking of 7050 aluminum alloys and ASTM A470 steel in the turbo-expander and steam/gas turbines industry can cause expensive catastrophic failures especially in those turbo-machinery systems performing in hostile corrosive environments. Commercially available inhibitors were investigated for their effectiveness in reducing and controlling the corrosion susceptibility. Cyclic polarization behavior for samples in the 1.0% and 5.0% inhibitors showed a shift in the passive film breakdown potential indicating more protective films. The substantial increase in the passivation range has favorable consequences for neutralizing pitting and crevice corrosion cell chemistry. The strain to failure and tensile strength from the slow strain rate stress corrosion cracking studies for both alloys showed pronounced effects of corrosion inhibition in the environment to retard SCC; the fractographic analysis showed a changed morphology with ductile overload as the primary failure mode instead of transgranular or intergranular cracking.