Solution chemistry within stress-corrosion cracks in alloy steels

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Abstract

The acidity and the concentrations of metal ions in the solution within progressing stress-corrosion(s.c.) cracks in some alloy steels were estimated. It was found that the solution is always pH 3·6–3·8 near the crack tip regardless of the particular type of alloy steel. In quenched-and-tempered alloy carbon steels the metallic elements are found in the solution in about the same proportions as in the steel. The relatively constant acidity produced during s.c.c. of the alloy steels is discussed in terms of the hydrolysis of Fe ions.

Résumé

Une estimation a été faite de l'acidité et des concentrations d'ions métalliques dans lasolution dans des fêlures de corrosion par contrainte (s.c.) en progression dans certains alliages d'acier. Il a été trouvé que la solution est toujours à un pH de 3,6 à 3,8 prés de la crête de la fêlure quelque soit le type particulier d'alliage d'acier. Dans les alliages d'acier au carbone trempés les éléments métalliques sont rencontrés dans la solution dans les mêmes proportions environ que dans l'acier. L'acidité relativement constante produite durant le fendillement s.c.c. des alliages d'acier est discutée en fonction de l'hydrolyse des ions de Fe.

Zusammenfassung

Der Säuregrad und die Konzentrationen von Metallionen in der Lösung innerhalbfortschreitenden Spannungskorrosion (s.c.) Rissen werden für einige Legierstahle geschätzt. Es wurde gefunden, dass die Lösung immer nahe der Spitze des Risses pH 3,6–3,8 ohne Rücksicht auf die besondere Art des Legierstahls ist. In abgeschreckten und getemperten, legierten Flusstahlen werden die metallischen Elemente in etwa den gleichen Verhältnissen wie beim Stahl in der Lösung gefunden. Der relativ konstante Säuregehalt, der während s.c.c. des Legierstahls entsteht, wird im Sinne von Hydrolyse der Fe Ionen behandelt.

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