ISIJ International
Online ISSN : 1347-5460
Print ISSN : 0915-1559
ISSN-L : 0915-1559
Regular Article
Analysis of the Initial Stage of Localized Corrosion on Zn and Zn Alloy Coated Steels by Photon Rupture Method
Masatoshi SAKAIRIKazuma ITABASHIHideaki TAKAHASHI
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2005 Volume 45 Issue 1 Pages 71-76

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Abstract

A photon rupture method, film removal by a focused pulse of pulsed Nd-YAG laser beam irradiation, has been developed as it enables oxide film stripping at extremely high rates without contamination from the film removal tools. In the present study, Zn and Zn-5mass%Al alloy coated steel specimens covered with protective nitrocellulose film were irradiated with a focused pulse of a pulsed Nd-YAG laser beam at a constant potential in 0.5 kmol m-3 H3BO3-0.05 kmol m-3 Na2B4O7 (pH=7.4) with/without 0.05 kmol m-3 of chloride ions to investigate the initial stage of localized corrosion. At low potentials, both samples reformed oxide film after the nitrocellulose films were removed by this method. The oxide film formation kinetics of Zn-55mass%Al follow an inverse logarithmic law, in agreement with Cabrera-Mott theory. However, at high potentials, localized corrosion producing corrosion products occured at the area where nitrocellulose film was removed. The dissolution current of the Zn coated steel samples is higher than that of Zn-5mass%Al coated samples at the same applied potential.

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© 2005 by The Iron and Steel Institute of Japan
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