Papers by Keyword: Cathodic Protection

Abstract: In this paper, it is proposed to investigate the influence of the parameter providing the rate of pipeline coating degradation on the protective length of cathodic protection systems (CPS). Comparison of the calculated values of the pipeline coating resistance with the predicted values is carried out according to the theoretical distribution of the pipeline coating resistance in time. The difference between the practical value of the parameter providing the rate of coating degradation of the considered pipeline section from the predicted one is determined. The dependence of the parameter providing the rate of pipeline coating degradation on the protective length of the CPS has been formed, which makes it possible to reduce the number of cathodic protection stations along the pipeline path at the design stage, and to diminish their energy consumption in the electrochemical protection system from corrosion of oil and gas pipelines.

Abstract: Generally, reinforcing steel in concrete is protected from corrosion. This happens because the cement content in the concrete has an alkaline effect. It can reduce the risk of corrosion, but the reinforcing steel may still corrode if exposed to a corrosive environment. One method of providing a high protection value against corrosion is the sacrificial anode cathodic protection system. This study aims to evaluate the effectiveness of the sacrificial anode cathodic protection on reinforced concrete. Three types of specimens were used in the study. The specimens were (a) unconnected anode-cathode specimen, (b) connected anode-cathode (design 1), and (c) connected anode-cathode (design 2). The dimensions of the concrete specimen are 1000 mm in length, 100 mm in width, and 100 mm in height. Profometer 5+ was used to locate the reinforcing steel in the concrete. In this study, the condition of the protected criteria of reinforced concrete was achieved within 30 weeks in 2019 after wet-dry cycle treatment in 3.5% NaCl media, and thus, the specimen was exposed in an open air for one year. In 2020, all of the specimens were treated again with a wet-dry cycle for 3 weeks to measure the potential value of the reinforcing steel after a year. The measurement result of the corrosion potential value after one year showed that the specimen (c) had a potential value of -884.67 mV. While the specimen (b) had a potential value of -689 mV. These results show that the specimen (c) still within the protected criteria based on the NACE standard after one year of exposure, whereas the specimen (b) is no longer protected after one year of exposure.

Abstract: The paper is aimed to the study of the corrosion-fatigue behavior of high strength steels for offshore pipelines. Tests have been performed in order to study fatigue crack growth in synthetic seawater under cathodic protection. The tests have been carried out on three different steel grades from 65 to 85 ksi with tempered martensite and ferrite-bainite microstructures. The effect of stress intensity factor, cathodic protection potential and cyclic loading frequency is shown.

Abstract: Cathodic protection induces the formation of a calcareous layer has been shown to improve metal protection against corrosion by reducing the oxygen diffusion on the metal surface. The present study focuses on the electrochemical scaling induced by the application of cathodic polarisation. A combination of non-invasive in-situ electrochemical techniques and electrochemical impedance spectroscopy was used. Metal/electrolyte interface behaviour was studied using voltammetry to determine the controlling anodic and cathodic reactions. One-week long experiments were conducted. Applied potential –1.2 V_SCE was shown to enable the formation of CaCO₃ allotropes calcite and aragonite, and brucite due to increased interfacial pH which resulted in the formation of hydrogen at the electrode surface. Time constants from bode plots for applied potential –1.2 V_SCE also illustrated the inhomogeneity of the calcareous layer. Modelling of polarisation curves illustrated a “passivation” phenomenon which resulted from formation of hydroxyl cations. This was further validated by bode plots with the added information on the diffusion reaction process. High frequency behaviour showed a steady increase in the electrolyte resistance which may be attributed to the formation of the calcareous layer. Evidence of the initial Mg-gel porous layer, which precedes the formation of brucite, was found.

Abstract: In this paper, sample of Eu-doped SrTiO₃ was synthesized using hydrothermal method, in which the Eu (NO₃)₃ and Sr (OH)₂ were as the Eu and Sr source. X-ray diffraction (XRD), scanning electron microscope (SEM) were used to characterize the structure and ingredient of the as-prepared samples. The results show that high-purity of SrTiO₃ was prepared and structure of SrTiO₃ without change with Eu doping. Also, performance of cathodic protection of stainless steel was tested in the photoelectricity cell. Furthermore, the mechanism of the improvement by the rare earth was also detected.

Abstract: This paper presents the cathodic protection of steel embedded concrete of aluminum based alloy in brackish mud. In this experiment, aluminum based alloys containing 5% zinc, 2% magnesium, and 0.5-2% stannum were fabricated. These elements were added because they produce heat treatable alloys, improved anti friction characteristics, fluidibility, and contain highest strengthening effect on aluminum alloys. These alloys were tested as sacrificial cathodic protection for the standard steel embedded concrete exposed to sea water and brackish mud. Surface morphology of the samples after subjected to corrosion was investigated through scanning electron microscopy (SEM) and anode capacity test (efficiency test). The results revealed that sample with the composition of 95.6% of aluminum, 3.83% of zinc, and 0.19% of stannum showed the best performance hence it was selected for cathodic protection in brackish mud.

Abstract: Aluminum alloy is well-known as a sacrificial anode material which can provide higher-electrochemical capacities than other types of sacrificial anodes. Al-Zn-In-Si alloys are primarily used to protect steel structures for marine application. The electrochemical behaviors of aluminum sacrificial anodes were investigated using experimental set-up conformed to NACE standard TM0190-2012. The electrochemical capacity of Al-5 wt% Zn-0.015 wt% In-0.1 wt% Si alloy is about 2,600 Ah/kg. The results indicate that the electrochemical capacities of Al-Zn-In-Si based alloys are improved by addition of Ti. Al-5 wt% Zn-0.015 wt% In-0.1 wt% Si alloy with Ti addition can provide higher-electrochemical capacities up to 2,747 Ah/kg.

Abstract: The influence of flow velocity on the protectiveness of calcareous deposits which formed by cathodic protection in seawater was studied. The deposition process and the protectiveness of calcareous deposits were investigated by electrochemical impedance spectrum (EIS) and linear polarization resistance technique (LPR). The EIS results showed that the capacitive loops sizes decreased with increasing flow velocities, indicating that calcareous deposits formed at higher flow velocities provided poorer protectiveness. An exponential decrease of protectiveness with increasing flow velocities was observed, which was quantified by LPR. The results of SEM and XRD showed that aragonite of calcium carbonate deposited at lower flow velocities but magnesium hydroxide deposited at higher velocities.

Abstract: Nowadays, the cathodic protection is a common way of additional corrosion protection of buried structures. This protection is usually accompanied by cathodic polarisation on the protective potential of-850 mV(CSE). Its function is to prevent undesirable corrosion rates, in case the coating protection fails. Objective was to predict a state in terms of passivity or activity in which a carbon steel is in. And to do so, there is a monitoring of pH values by amphoteric metals, which would track pH changes of cathodically protected material in a soil. For pH detection, Al and Zn, were used. Main aim was to track corrosion rate of these amphoteric metals as a most reliable way to predict pH changes. Cathodic protection led to higher pH values of model soil located closely to surface of protected material. In case of carbon steel, alkalisation led to passive state and in the same time amphoteric metals could exist in active state. The aim of this work was to clarify usage of monitoring the corrosion rate of amphoteric metals for detection of pH values influenced by cathodic polarisation.Graphical abstract: Fig. 1 Kinetic and thermodynamic demonstration of passivation of cathodically protected steel

Abstract: The roof of the Ensor-gallery at Ostend is a cylindrical vault, constructed as a coarse grillage of reinforced concrete, with embedded reinforced concrete roof panels with prismatic glass tiles. The concrete ribs of the roof shell were heavily damaged by long term exposure to the chloride containing sea air, causing severe reinforcement corrosion. The paper presents the experimental data on the degradation, as well as the alternative approach used in the restoration project to avoid the loss of a major part of the authentic material. The approach is based on a combination of galvanic cathodic protection with embedded and bored in sacrificing anodes, the application of a chloride inhibiting impregnation followed by a realkalising treatment on the preserved parts, concrete repair and reconstruction with a self-compacting, shrinkage compensating, polymer modified repair mortar. Completely denuded steel reinforcement bars were replaced by glass fiber reinforced polyester rods.