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Carbon steels are widely used in ocean engineering due to their cost effectiveness, ease of manufacture, and excellent weldability. However, the attachment of macro-fouling organisms in seawater poses a serious threat to the integrity of carbon steel structures. In this experiment, carbon steel plates were immersed in the Dalian Sea area from January to October to investigate the effects of macro-fouling on corrosion propagation. The electrochemical measurement indicated that the propensity for the corrosion of Q235B is ranked as ascidians > mussels > barnacles. The characterization results indicated that various marine organisms significantly influenced the corrosion behavior of Q235B carbon steel immersed in natural seawater. The colonization of barnacles inhibited corrosion at the barnacle central area, and the presence of barnacle covering caused crevice corrosion at the edges of the barnacle due to oxygen concentration cells. The presence of ascidians resulted in general corrosion due to the locally high conductivity and ion diffusion rate. A relatively compact rust layer, which exhibited localized defects, was observed beneath the mussels. Seawater had the ability to penetrate the rust layer through these defects, leading to the formation of pitting corrosion on the metal substrate. [ABSTRACT FROM AUTHOR]

The initiation of erosion and the coupled damage of erosion and corrosion on the surface of X65 pipeline steel with varying applied anodic currents were online monitored using the electrical resistance (ER) method. Results show that ER method in conjunction with anodic polarization was a highly effective approach for the investigation of the interaction effect between erosion and corrosion, which can be used to quickly and conveniently obtain the synchronously changed erosion and corrosion rates. The critical impact energy is a key parameter of sand particles to induce erosion damage on the steel surface, which can remove the flaky cementite at the edge of the pits. The threshold anodic current density that can cause a synergic effect between erosion and corrosion of X65 pipeline steel can be quantitatively fitted based on the erosion rates under varying anodic currents. [ABSTRACT FROM AUTHOR]

A partial pre-rusted wire beam electrode (WBE) was designed to study the influence of the rust layer on rebar corrosion in the carbonated simulated concrete pore solution (SCPS). The results show that the passive film generated on the pre-rusted steel area is more fragile than that formed on the fine polished steel area in carbonaceous media. Nevertheless, the pitting corrosion resulting from the presence of chloride ions still tends to occur on the fine polished steel surface due to the local acidification process being hindered by the rust layer. The rust layer could play a more important role than the passive film in inhibiting the initiation of chloride-induced corrosion on rebar. The expansion path of the corrosion product would be blocked by the rust layer, leading to the pit propagating in the fine polished region. Furthermore, the growth of pitting corrosion is greatly accelerated due to the catalytic cathodic reaction of the rust layer. [ABSTRACT FROM AUTHOR]

In addition to the development of ocean engineering, many ships and offshore structures have been constructed in recent years for use in shipping, oil and gas exploration, clean energy, mining and military purposes. Metallic materials such as high-strength steels, stainless steels, copper alloys and titanium alloys are widely used to build the required marine equipment. The new alloy has a wide application range in corrosion and erosion-corrosion cases in seawater. [Extracted from the article]

Series of displacement tests of water by cold n-hexanol (below 0 °C) in a straight tube were conducted to investigate the freezing-accompanied displacement process, which occurs during the cryogenic fracturing process. The interrelationship between water freezing and displacement flow was studied. It was found that the displacement flow could significantly affect the water distribution in the flow channel. Along with the displacement proceeding, the n-hexanol overtook the water in the flow direction gradually, and the water in the center of the channel was driven to the edge area. Moreover, the initially integrated water phase split into several parts during the displacement process. Once the water freezing occurred, two typical ice blockage patterns, i.e., complete ice blockage and incomplete ice blockage, were observed. In incomplete ice blockage pattern, the channel cross-section was partly occupied by the ice phase, which mainly affected the rate of subsequent fluid flow. In complete ice blockage pattern, the channel cross-section was fully occupied by the ice phase, which cut off the fluid flow in the original direction. Based on the test results, the influences of the initial water temperature, initial water column length and flow rate of n-hexanol on the formation of different ice blockage patterns are discussed. The decrease of the initial water temperature and the increase of the initial water column length are preferred to induce the occurrence of complete ice blockage. However, changing n-hexanol flow rate could lead to the occurrence of both incomplete ice blockage and complete ice blockage, which depends on the actual situations. [ABSTRACT FROM AUTHOR]

This paper firstly provides an overview of major efforts made over the past several decades on developing the test apparatus for the study of erosion-corrosion of ferrous-based steels. The merits and the application range of the set-ups, i.e., rotating disc/cylinder electrode system, slurry jet impingement rig, and test flow loop, are introduced. Secondly, the advantages and limitations of both non-electrochemical and electrochemical methods used for the measurement of erosion-corrosion are presented. Thereafter, the interaction between erosion and corrosion using a cyclic erosion-corrosion method was introduced. The synergy between erosion and corrosion for the steels under the passive state were analyzed on the basis of the breakdown and restoration of the passive film. In addition, the difference between the obtained erosion-enhanced corrosion and the corrosion-enhanced erosion using different experimental methods for steels under active corrosion was discussed. Finally, the interaction between the localized corrosion and erosion was studied through the dynamic change of the local current distribution revealed by the wire beam electrode. [ABSTRACT FROM AUTHOR]

In this paper, a new kind of carbon steel (CS) and stainless steel (SS) galvanic sensor system was developed for the study of rebar corrosion in different pore solution conditions. Through the special design of the CS and SS electronic coupons, the electronic resistance (ER) method and zero resistance ammeter (ZRA) technique were used simultaneously for the measurement of both the galvanic current and the corrosion depth. The corrosion processes in different solution conditions were also studied by linear polarization resistance (LPR) and the measurements of polarization curves. The test result shows that the galvanic current noise can provide detailed information of the corrosion processes. When localized corrosion occurs, the corrosion rate measured by the ER method is lower than the real corrosion rate. However, the value measured by the LPR method is higher than the real corrosion rate. The galvanic current and the corrosion current measured by the LPR method shows linear correlation in chloride-containing saturated Ca(OH)₂ solution. The relationship between the corrosion current differences measured by the CS electronic coupons and the galvanic current between the CS and SS electronic coupons can also be used to evaluate the localized corrosion in reinforced concrete., Competing Interests: The authors declare no conflict of interest.