11285 Effect of Electrolyte Composition on Near-neutral pH Stress Corrosion Crack Propagation

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Product Number: 51300-11285-SG

ISBN: 2011 11285 CP

Author: Andrey Marshakov, Roman Bogdanov, Vasily Ignatenko, Tatjana Nenasheva and Andrey Arabey

Publication Date: 2011

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The electrolyte composition was shown to affect the crack growth rate in pipeline steel X70. Citrate buffer (?? 5.5) and a mixture of NS4 solution with borate buffer (pH 7.0) were used as background solutions under static and cyclic loading, respectively. Various substances were added to the citrate buffer solution in order to affect anodic dissolution (AD) and hydrogen absorption (HA) of the metal. AD inhibitors decrease the crack growth rate. Sulfide, carbonate and phosphate ions, which stimulate the AD process, accelerate crack propagation in weakly-acidic solutions. Thiourea stimulates the ?D process in buffered NS4 solution and accelerates the crack growth in this solution. The effects of HA promoters may vary. Their influence on the crack propagation could be connected with the activating effect of atomic hydrogen on the anodic dissolution of iron. The data obtained testify that anodic dissolution of the metal is the governing mechanism in the SCC of pipe steel X70 in the vicinity of the corrosion potential.

Key words: pipeline steel, near-neutral pH environment, crack propagation, electrolyte composition, anodic dissolution, hydrogen absorption.