Film Breakdown and Anodic Dissolution during Stress Corrosion Cracking of Carbon Steel in Bioethanol

Abstract

The stress corrosion cracking (SCC) behavior of X-65 carbon steel was investigated in simulated fuel-grade ethanol (SFGE) using the slow strain rate test method, potentiodynamic polarization, electrochemical impedance spectroscopy, open-circuit potential, and potentiostatic current monitoring. Results indicate that crack initiation on carbon steel in the SFGE environment is associated with plastic deformation in the material, which leads to a surface film breakdown. The competition between active anodic dissolution and repassivation ahead of the crack tip controlled the propagation of these cracks in SFGE. Within the anodic dissolution range, both crack density and crack growth rate in the through-thickness direction increased as the potential increased. The applied cathodic potential eliminated the SCC in this system. The mode of SCC for the carbon steel in aerated SFGE was predominately transgranular.

Mechanistic study of stress corrosion cracking of carbon steel in ethanol

“…The SCC of carbon steel in ethanol has been proposed to occur by initiation by film breakdown, which is followed by crack growth controlled by a competition between anodic dissolution and repassivation 9, 16. No SEM observations have been previously published to support this mechanism.…”

“…In this situation, there should be a zone of active steel surface near the crack tip and passivated oxide covered steel surface on the crack walls and outside the crack 9. Results from a recent study by Lou et al 16 indicated that the initiation of the SCC cracks is associated with plastic deformation in the steel, which leads to a surface film breakdown and to the propagation of the cracks controlled by the competition between active anodic dissolution and repassivation at the crack tip as proposed by Beavers et al 9. This may explain the effect of galvanic coupling to corroded steel increasing the susceptibility to SCC in FGE.…”

Effect of MnS inclusion dissolution on carbon steel stress corrosion cracking in fuel-grade ethanol

“…The roles of different environmental parameters on the ethanol SCC are well known [2,[4][5][6][7][8][9][10][11][12][13][14][15][16], but the conditions within the ethanol SCC crack are still not known very well. One way to get information of the conditions within the SCC crack is to study the dissolution of the manganese sulfide inclusions.…”

Revisión y estado del arte de la corrosividad del etanol y sus mezclas con gasolina

“…Concluyeron que la probabilidad de aparición del fenómeno de la corrosión bajo tensión en los materiales ensayados, depende íntimamente del contenido en cloruros presentes en el etanol comercial. Lou et al [63] , estudiaron con detalle el mecanimo de corrosión de un acero al carbono en etanol. Observaron que, una vez iniciada la grieta, existe una competición entre la disolución anódica y la repasivación del sistema metá-lico, hecho que determina la velocidad de crecimiento de la grieta.…”