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07255 Relations between Seawater Ennoblement Selectivity and Passive Film Semiconductivity on Ni-Cr-Mo Alloys

Product Number: 51300-07255-SG
ISBN: 07255 2007 CP
Author: Farrel J. Martin, Edward J. Lemieux, Stephen C. Dexter, and Matthew Strom
Publication Date: 2007
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The present work compares seawater corrosion potential ennoblement behavior from two marine exposure locations using Ni-Cr-Mo alloys. Alloy 625 (UNS N06625), Alloy 276 (UNS N10276), Alloy 4 (UNS N06455), Alloy 59 (UNS N06059) and Alloy 686 (UNS N06686) were exposed for periods of up to one year at the U. S. Naval Research Laboratory in Key West, Florida (NRLKW), and the University of Delaware College of Marine Studies at Lewes, DE (Udel CMES). Open-circuit corrosion potential (OCP) measurements at these two locations demonstrated that the highest achievable ennoblement-related corrosion potential differed by as much as 100 mV between locations, with higher potentials measured at the Udel CMES site. A further analysis involving alloy composition demonstrated that there appears to be some ennoblement biofilm selectivity related to chromium and iron that influences the highest observable OCP’s, in the coastal waters at Udel CMES. No such sensitivity to alloy composition appears to be present in the blue ocean waters of NRLKW. Passive film semiconductive properties are also reported as a result of impedance-derived Mott-Schottky analysis and photocurrents, with accompanying discussion of their relation to composition for the Ni-Cr-Mo alloys under investigation.
The present work compares seawater corrosion potential ennoblement behavior from two marine exposure locations using Ni-Cr-Mo alloys. Alloy 625 (UNS N06625), Alloy 276 (UNS N10276), Alloy 4 (UNS N06455), Alloy 59 (UNS N06059) and Alloy 686 (UNS N06686) were exposed for periods of up to one year at the U. S. Naval Research Laboratory in Key West, Florida (NRLKW), and the University of Delaware College of Marine Studies at Lewes, DE (Udel CMES). Open-circuit corrosion potential (OCP) measurements at these two locations demonstrated that the highest achievable ennoblement-related corrosion potential differed by as much as 100 mV between locations, with higher potentials measured at the Udel CMES site. A further analysis involving alloy composition demonstrated that there appears to be some ennoblement biofilm selectivity related to chromium and iron that influences the highest observable OCP’s, in the coastal waters at Udel CMES. No such sensitivity to alloy composition appears to be present in the blue ocean waters of NRLKW. Passive film semiconductive properties are also reported as a result of impedance-derived Mott-Schottky analysis and photocurrents, with accompanying discussion of their relation to composition for the Ni-Cr-Mo alloys under investigation.
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07586 In Situ Investigation of the Passivation of Alloy C22 and of the Passive Films Formed on Alloy C22 in Acidic Electrolytes at Room Temperature and at 90 C

Product Number: 51300-07586-SG
ISBN: 07586 2007 CP
Author: Thomas M. Devine, Marcela Miyagusuku, and Scott Harrington
Publication Date: 2007
$20.00