Abstract
Water-line corrosion is a highly concentrated type of localized corrosion. The conventional single electrode method is limited in its ability to obtain the kinetic information of the corrosion occurrence and development processes. Herein, the coating deterioration and underlying metal corrosion processes in water-line area were studied by a small wire beam electrode to monitor the current density distribution. The distance between each electrode was very small (interval: 0.3 mm), thus facilitating it to approach the practical metal component with a continuous surface. The results showed that cathodic and anodic sites tended to be weak points of the coating at the initial stage. With the continuous degradation of the coating, the cathodic zone tended to occur in the above the anodic zone due to the effect of differential aeration cells (DACs). Subsequently, the cathodic zone expanded to the waterline and the polarity reversed to the anodic zone, causing the coating to peel and blister continuously from the bottom up. When the cathodic zone extended to the gas phase area above the water line, this area became the strongest cathodic zone under the action of the thin liquid film, thus significantly accelerating the corrosion of the base metal at the bottom. The present study aims to achieve an in-depth understanding of coating deterioration and underlying metal corrosion processes in the water-line area, providing a new means of directly visualizing the role of DACs played in water line corrosion.
Highlights
The phenomenon of water-line corrosion (WLC) that occurs along the gas–liquid–solid three-phase interface is generally considered to result from differential aeration cells (DACs) adjacent to the water line [1]
DACs, we introduced order to eliminate the impact of this random factor and better understand the effect of DACs, we introduced the concept of single-row current density [6]
The cathodic and Coating and underlying metal in the water-line area were anodic sites were randomly distributed across the coating due to the non-uniform water permeation studied using the wire beam electrode (WBE) technique in 3.5 wt.% NaCl solution
Summary
The phenomenon of water-line corrosion (WLC) that occurs along the gas–liquid–solid three-phase interface is generally considered to result from differential aeration cells (DACs) adjacent to the water line [1]. The high corrosion loss observed around 200 mm below the water line in the experiment was consistent with the results of classical laboratory studies [3]. This indicated that it was the result of DACs with the well-aerated. In the water-line area, the coating undergoes deterioration and the base metal undergoes localized non-uniform corrosion. Tothe resolve these issues, studied the In coating deterioration and the underlying corrosion process water-line area bywe a small. Addition, studying and underlying metal corrosion process in the water-line area by a small. Be of great value for for mechanism the development of WLC-resistance coating optimization of evaluation the development of WLC-resistance coating and optimization of evaluation methods
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