Localized CO2 corrosion propagation at moderate FeCO3 supersaturation initiated by mechanical removal of corrosion scale

Abstract

The propagation of localized CO 2 corrosion was investigated at moderate iron carbonate supersaturation using an artificial defect method with re-formed corrosion scale. A mechanical tool was developed which locally removed pre-formed iron carbonate scale and initiated localized corrosion at a FeCO 3 supersaturation of 3-10. The localized corrosion rate was calculated based on electrochemical measurement using a simplified algorithm and was also measured at the deepest part of the defect using scanning electron microscopy. Localized corrosion was driven by a galvanic cell established between the two surfaces exposed in the artificial defect where an open circuit potential difference was maintained.

13C isotopic labeling to decipher the iron corrosion mechanisms in a carbonated anoxic environment

“…As suggested by the literature, this partial breakdown of the siderite inner layer implies the development of a local galvanic cell between the scale‐covered surface (cathode) and the scale‐free surface (anode), activating iron oxidation, Fe → Fe 2+ + 2e − (Step 3). [ 16,17,37–40 ]…”

Study on porous layer formation kinetics under CO2‐aqueous conditions via partial‐bounceback lattice Boltzmann method

“…9,10 The role that the FeCO 3 layer performs during CO 2 corrosion is controversial, especially referring to its involvement in localized corrosion and passivation. [11][12][13][14][15][16] However, it is indubitable that the presence of a FeCO 3 layer is able to change the dynamics of CO 2 corrosion significantly. 7,10,[17][18][19] The porosity, as a critical parameter of the microstructure, is highly related to the protectiveness of the product layer.…”

“…As a key parameter in Equation (), K sp is the solubility product of FeCO 3 , which has a strong correlation with temperature and ionic strength 9,10 . The role that the FeCO 3 layer performs during CO 2 corrosion is controversial, especially referring to its involvement in localized corrosion and passivation 11–16 . However, it is indubitable that the presence of a FeCO 3 layer is able to change the dynamics of CO 2 corrosion significantly 7,10,17–19 .…”

Investigation of the evolution of an iron carbonate layer and its effect on localized corrosion of X65 carbon steel in CO2 corrosion environments

“…In addition, pseudo-passivation was found to be one factor clearly related to pit initiation and propagation, with pits in excess of 30 µm deep being recorded soon after a sudden increase in Open Circuit Potential (OCP). Nevertheless, mechanical and/or chemical removal of the FeCO3 layer is believed to be the main reason for localized corrosion of carbon steel, driven by the galvanic interactions between the local bare metal surface and the significantly larger areas of metal surface covered by the corrosion product [25,28,29]. However, the question arises as to whether localized corrosion, with similar mechanisms to crevice corrosion attack, occurs at the metal surface underneath a densely covered layer without any macroscopic damage to the FeCO3 layer.…”