SEDL / STP / STP558-EB / STP32167S

Accelerated Testing of Marine Grade Steels—A Localized Corrosion Approach

Johnston, RRM
Senior research officer and research officer, BHP Melbourne Research Laboratories, Clayton, Victoria

Lloyd, CP
Senior research officer and research officer, BHP Melbourne Research Laboratories, Clayton, Victoria

Pages: 18    Published: Jan 1974

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Abstract

Factors affecting local cell action such as the presence of non-metallic inclusions in steel and the contribution of ohmic control (iR drop) in the electrolyte are discussed. The importance of local action in the marine environment and the poor reliability of current accelerated tests for marine grade steels are pointed out. An investigative technique, developed from earlier work, is described in which the specimen has been incorporated in the form of a horizontal rotating disk enabling solution hydrodynamics to be readily defined. The intensity of local cells is displayed in real time as a magnified contour map of the corroding specimen surface. Effects of test electrolyte composition including ionic strength and concentration of cathodic species have been studied on a model galvanic system, a steel containing sulphide inclusions, and two low-alloy marine grade steels.