Corrosion behavior of X65 pipeline steel in coastal areas

Abstract

Purpose To study the corrosion behavior of pipeline steel in coastal areas, a tidal seawater macro-cell corrosion device was built using a cycle soaking tank and a macro-cell corrosion facility to simulate the corrosion behavior of pipeline steel in a simulated coastal environment (dry and wet alternations during seawater-soil corrosion macro-cell processes). Design/methodology/approach The corrosion behaviors were studied via the weight loss method, electrochemical methods and morphological observations on corrosion. Findings The results show that during the initial stage of tidal seawater/soil macro-cell corrosion process of the X65 steel, the working electrode on the seawater side is the anode of the macro-battery. As corrosion progresses, the anode and the cathode of the macro-battery become inverted. As the area ratio and the dry – wet ratio increase, the time of anode and cathode inversion shortens. Galvanic current density decreases as the dry – wet ratio increases and increases as the area ratio increases. The corrosion process of macro-cell is affected by the reversal of anode and cathode. After the reversal of anode and cathode, the corrosion rate is mainly controlled by dry – wet alternating corrosion. Originality/value The corrosion behavior of a pipeline steel in a coastal environment was studied using a tidal seawater macro-cell corrosion device. The synergism effect between the tidal seawater and seawater-soil macro-cell on corrosion behavior was clarified.

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“…The magnitude of the resistance and the thickness of the rust layer and composition are related to the CPEr as a constant phase element, including the rust layer and the capacitance of the electrolyte solution. Rc is the charge transfer resistance of the redox process, CPEc represents the double-layer capacitance structure of the inner rust layer, and W is the resistance caused by concentration polarization [33,34]. he relationship between the sample steel and the rust resistance of different Cu contents after 30, 80, and 120 cycles is shown in figure 14.…”

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“…During storage, gaps between steel plates facilitate a local occluded cell effect, lead to intensified acidification of pits and further accelerate pit development (Frankel and Sridhar, 2008; Sun et al , 2021b). According to reports, there are frequent accidents for pitting corrosion failure during storage of hot-rolled sheets, causing major accidents and huge economic losses (Hou et al , 2017; Li et al , 2015; Sun et al , 2019). When these long-term stored steel plates are in use, pits tend to be stress corrosion cracking initiation sites under the action of applied stress(Liu et al , 2009; Zheng et al , 2013; Sun et al , 2021a; Ma et al , 2021).…”