The stimulating effect of numerous soil electrolyte components, specifically, bicarbonate, sulphide, and phosphate, on the growth of corrosion cracks in pipeline steel X-70 exposed to pH 5.5 citrate buffer and a mixture of NS4 solution with a borate buffer (pH 7) originates from the accelerated active iron dissolution that occurs in the presence of these compounds. The soil electrolyte components that do not affect the kinetics of the anodic reaction in this corrosive environment, such as the nitrate anions and calcium cations, do not alter the rate of crack growth in pipe steel. Anodic corrosion inhibitors enhance the resistance of pipe steel against corrosion cracking under static loading, e.g., Catamin AB decreases the rate of crack growth in a sulphide-containing medium by approximately a factor of four. Introducing hydrogen absorption promoters to a citrate buffer solution does not accelerate crack growth. It confirms that the local anodic dissolution of the metal is the predominant crack growth mechanism in pipe steel X70 in pH 5.5 citrate buffer at the corrosion potential. The cyclic crack resistance of pipe steel in NS4 buffer solution at pH 7.0 is mainly determined by the regularities of the metal fatigue fractures. It confirms that metal dissolution occurs in the tip of crack. Anodic dissolution-induced plasticity may play an important role in crack growth at small amplitudes of cyclic loading.
Effect of electrolyte composition on crack growth rate in pipeline steel
Einfluss der Elektrolytzusammensetzung auf die Risswachstumsgeschwindigkeit von Rohrstahl
Corrosion Science ; 83 ; 209-216
2014
8 Seiten, 8 Bilder, 4 Tabellen, 45 Quellen
Aufsatz (Zeitschrift)
Englisch
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