This paper deals with the influence of the cathodic protection conditions on the hydrogen absorption by underground steel pipes for natural gas transport in media containing thiosulfate. Hydrogen electrochemical permeation tests were performed in soil-like media with different concentrations of thiosulphate. The effect of applied potential as well as that of the medium composition on the hydrogen absorption were analyzed. The deposit formed during cathodic polarization on the protected steel surface was examined by scanning electron microscopy and X-ray diffraction. The results confirmed the catalytic effect of the thiosulphate on the hydrogen absorption. However it was shown that a high negative electrode potential as well as a calcium-magnesium deposit formed during the cathodic polarization can inhibit this catalytic action. The mechanism of the inhibition seemed to be unique and was attributed to a distance effect between the electronegative catalytic species and the metallic surface due to either an electrical field (created by a high negative potential) or a physical barrier (created by a calcium-magnesium deposit).
Hydrogen absorption by cathodically protected underground steel piping in thiosulfate containing media
Corrosion Science ; 40 , 4-5 ; 619-629
1998
11 Seiten, 12 Quellen
Aufsatz (Zeitschrift)
Englisch
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