Effect of AC interference on the corrosion behavior of cathodically protected mild steel in an artificial soil solution. Part I: Investigation on formed corrosion product layer

Abstract

AC-induced corrosion is a big threat even for cathodically protected pipelines nowadays. While this phenomenon was intensively investigated in the last decades, the corrosion mechanisms due to AC interference remain unclear. In the present work, investigations on the surface processes on cathodically protected mild steel during AC polarization have been performed. They utilized high-speed potential measurements that have demonstrated the influence of the polarization parameters on the resulting alternating voltage. The corrosion product layer was characterized with scanning electron microscopy, electron probe microanalysis, and Raman spectroscopy, which clearly show the effect of the parameters of the applied alternating current on the surface under different cathodic protection (CP) conditions. It was demonstrated that the properties of the formed corrosion product layer, meaning the layer thickness, amount of oxygen, and so on, is not only dependent on the AC polarization parameters but also on the CP potential itself.

AC corrosion of steel pipeline under cathodic protection: A state‐of‐the‐art review

“…For example, the optical microscope provides a macroscopic view of the surface morphology, while the scanning electron microscope (SEM) allows for the observation of metal corrosion phenomena at a microscopic level. [23,25,54] Techniques such as energy dispersive spectrometry (EDS) and electron microprobe analysis (EMPA) are used to analyze the composition of corrosion products. [23,54] Figure 6 shows four typical surface examinations for X60 pipeline steel after 50 h of AC interference.…”

“…[23,25,54] Techniques such as energy dispersive spectrometry (EDS) and electron microprobe analysis (EMPA) are used to analyze the composition of corrosion products. [23,54] Figure 6 shows four typical surface examinations for X60 pipeline steel after 50 h of AC interference. The first subfigure shows the SEM image.…”

“…[ 23,25,54 ] Techniques such as energy dispersive spectrometry (EDS) and electron microprobe analysis (EMPA) are used to analyze the composition of corrosion products. [ 23,54 ]…”