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1 – 10 of 126Clément Génin, Marc Jeannin, Anne-Marie Grolleau and Philippe Refait
The purpose of this study is to investigate cathodic protection (CP) efficiency in the tidal zone and its associated processes.
Abstract
Purpose
The purpose of this study is to investigate cathodic protection (CP) efficiency in the tidal zone and its associated processes.
Design/methodology/approach
Specific features of CP in the tidal zone, that is, persistence of a thin seawater film and insufficient cathodic potential due to ohmic drop, were addressed. In this preliminary study, carbon steel electrodes were polarized at two cathodic potentials (correct or insufficient protection) while immersed in 1 mm or 5 mm thick natural seawater layers. After CP interruption, the protective ability of the layers covering the steel electrodes was studied using various electrochemical methods, including electrochemical impedance spectroscopy. The layers were characterized by XRD.
Findings
The protective ability of calcareous deposits was increased in thin seawater films. Insufficient CP could promote protective aragonite/corrosion products layer.
Originality/value
The combined effects of thin seawater film and applied potential were never addressed, and the conclusions drawn from this preliminary study give new insight on the efficiency of CP in the tidal zone.
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Trials to develop environmentally friendly marine paints based on natural materials as replacement for copper and tin compounds for fouling and marine corrosion control.
Abstract
Purpose
Trials to develop environmentally friendly marine paints based on natural materials as replacement for copper and tin compounds for fouling and marine corrosion control.
Design/methodology/approach
Green algae, tubeworms in dead powder form and garlic were used as natural anti‐fouling components in the paints developed. Electrochemical technique was employed for testing the potential of both tubeworms and garlic in terms of inhibition of steel corrosion in seawater. Marine paint formulations containing each of the three selected natural materials were applied onto PVC and un‐primed steel surface, which were immersed in natural seawater for the assessment of their anti‐fouling and anti‐corrosion properties. The results of visual assessment and seawater analysis were also used for such an evaluation.
Findings
Tubeworms act as mixed type inhibitor while garlic affects the potential cathodic process of steel in seawater. Tubeworms‐based paint, with 25 per cent in the dry paint film, could protect steel surface from marine corrosion up to 7 months. The paints containing algae and garlic, and the corresponding algae/garlic free paints, resisted slime film formation. Steel and PVC coated surfaces with paint containing algae showed the best anti‐fouling potential within the prepared series.
Research limitations\implications
The investigation only involved the application of the dead form of green algae and tubeworms as effective pigments in the developed paints. It is recommended that further research should focus on extracting and identifying the active components in each organism against fouling and marine corrosion.
Practical implications
The paint formulations developed (containing 25 per cent by weight tubeworms in the paint film) could be used to protect un‐primed steel surface against fouling and marine corrosion for a reasonably long duration.
Originality/value
The application of one paint formulation on un‐primed steel surface for its protection from both fouling and marine corrosion is novel. The electrochemical studies of steel in natural seawater in presence of tubeworms and garlic are original.
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The purpose of this paper is to evaluate the effect of seawater temperature on the corrosion behaviour of 90‐10 cupronickel alloys. Also, to investigate the effect of thiosulphate…
Abstract
Purpose
The purpose of this paper is to evaluate the effect of seawater temperature on the corrosion behaviour of 90‐10 cupronickel alloys. Also, to investigate the effect of thiosulphate additions (one of the major sulphide oxidation products in seawater) on the alloy corrosion rate in seawater.
Design/methodology/approach
Potentiodynamic polarization measurement (DC) was used to estimate the corrosion rate of the cupronickel alloy in seawater with and without thiosulphate species (50‐650 ppm).
Findings
It was observed that the cupronickel alloy suffered accelerated corrosion as the seawater temperature was raised from 25 to 50 or 80°C. The increase in the corrosion rate was found to correspond well with the negative shift in the free corrosion potential. Thiosulphate addition was found to depend on the test temperature. At 25°C, thiosulphate activated the alloy dissolution rate and the higher were the thiosulphate concentrations, the higher was the corrosion rate. At 50 or 80°C, however, thiosulphate promoted the dissolution rate at early stages, but seemed to interfere with the surface film formation later on, producing a black film that effectively decreased the alloy corrosion rate. At higher potentials, however, the film became non‐protective, leading to accelerated corrosion once again.
Originality/value
This paper explains the corrosion behaviour of 90‐10 cupronickel alloys in seawater as a function of test temperature and thiosulphate additions.
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This paper aims to investigate the effect of introducing nano-ceria (CeO2) particles to the epoxy coatings on mild steel in natural seawater.
Abstract
Purpose
This paper aims to investigate the effect of introducing nano-ceria (CeO2) particles to the epoxy coatings on mild steel in natural seawater.
Design/methodology/approach
The epoxy–ceria nanoparticles were coated with mild steel using a wire-wound draw-down bar method. The effects of ceria nanoparticles on the corrosion resistance of epoxy-coated samples were analyzed using scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS).
Findings
Localized measurements such as oxygen consumption and iron dissolution were observed using SECM in natural seawater in the epoxy-coated sample. The increase in film resistance (Rf) and charge transfer resistance (Rct) values by the addition of nano-ceria particles in the epoxy coating was measured from EIS measurements after wet and dry cyclic corrosion test. Scanning electron microscope (SEM)/energy dispersive X-ray spectroscope (EDX) analysis showed that complex oxides of nano-ceria were enriched in corrosion products at a scratched area of the coated mild steel after corrosion testing. Focused ion beam-transmission electron microscope (FIB-TEM) analysis confirmed the presence of the nanoscale oxide layers of ceria in the rust of the steel.
Research limitations/implications
The tip current at −0.70 V for the epoxy–CeO2-coated sample decreased rapidly because of cathodic reduction of the dissolved oxygen. The increase in film resistance (Rf) and charge transfer resistance (Rct) values by the addition of nano-ceria particles in the epoxy coating were measured from EIS measurements after wet and dry cyclic corrosion test.
Practical implications
The presence of complex oxide layers of nano-ceria layers protects the coated steel from rusting.
Social implications
The use of this nano-ceria for corrosion protection is environment-friendly.
Originality/value
The results of this study indicated the significant effect of nano-ceria particles on the protective performance and corrosion resistance of the epoxy coating on mild steel. The dissolution of Fe2+ was lower in the epoxy–ceria nanoparticle-coated mild steel than that of the epoxy-coated mild steel resulting in a lower anodic current of steel. The increase in film resistance and the charge transfer resistance showed that the nano-ceria particles and the formation of complex oxides provide better barrier protection to the coating metal surfaces.
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Mariela Rendón Belmonte, José Trinidad Pérez Quiroz, Benjamín Valdez Salas, Miguel Martínez Madrid, Andrés Torres Acosta, Jesús Porcayo Calderón and Miguel Schorr Wiener
The purpose of this paper is to characterize the surface of steel under cathodic protection while submerged in seawater, to understand the mechanism that controls the operation of…
Abstract
Purpose
The purpose of this paper is to characterize the surface of steel under cathodic protection while submerged in seawater, to understand the mechanism that controls the operation of the protection system.
Design/methodology/approach
Steel rods were immersed in seawater and NaCl solution with applied cathodic protection. The experimental methodology included monitoring of corrosion potential (Ecorr), galvanic current (Igalv) protection potential (Eprotection) and the depolarization potential of steel during the time of exposure. In addition, the chemical composition of the steel surface was assessed using a Scanning Electron Microscope (SEM).
Findings
In this research it was determined that the effectiveness of the CP system was mainly attributable to the formation of an iron oxide film on the steel surface.
Research limitations/implications
It is necessary to carry out analysis of the chemical composition of deposits formed on the steel surface, perhaps using X‐ray diffraction (XRD), to verify the presence of a protective oxide.
Practical implications
Deposits on the steel surface have the beneficial effect of reducing the current required for efficient protection. Deposit formation therefore is of economic interest, as it decreases the cost of protection.
Originality/value
A unique feature of cathodic protection in seawater is the formation of calcareous deposits on metal surfaces. Advantageous aspects of these deposits, such as decrease in cathodic current requirement, have been investigated by various authors from various viewpoints. However, very little attention has been paid to the impact of any iron corrosion product films; the present paper contributes useful understanding and explains the importance of the mechanism that controls the operation of the protection system.
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The purpose of this study is to use polybenzoxazine (Pbz) functionalized ZrO2 nanoparticles to synthesize polyurethane (PU)-PbZ/ZrO2 nanocomposite. The results derived from the…
Abstract
Purpose
The purpose of this study is to use polybenzoxazine (Pbz) functionalized ZrO2 nanoparticles to synthesize polyurethane (PU)-PbZ/ZrO2 nanocomposite. The results derived from the electrochemical impedance spectroscopy (EIS) and polarization studies indicated the superior anticorrosive activity of PU-Pbz/ZrO2 nanocomposite coatings compared to those of plain PU coatings. The decreased corrosion current was detected on the scratch of the PU-Pbz/ZrO2 nanocomposite-coated mild steel surface by scanning electrochemical microscopy (SECM) compared to other studied coatings. The superior anticorrosive and mechanical properties of the proposed nanocomposite coatings provide a new horizon in the development of high-performance anticorrosive coatings for various industries.
Design/methodology/approach
The Pbz functionalized ZrO2 nanoparticles were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) and thermogravimetric analysis (TGA) in terms of the structural, morphological and thermal properties of these coatings. A different formulation of coatings such as PU, PU-Pbz, PU-ZrO2 and PU-Pbz/ZrO2 were prepared and investigated for their corrosion protection performance on mild steel in natural seawater by electrochemical techniques. The surface morphological studies were done by SEM/EDX and XRD analysis.
Findings
The superior anticorrosive property of the proposed nanocomposite coatings provides a new horizon in the development of high-performance anticorrosive coatings for various industries. Addition of Pbz wrapped ZrO2 nanoparticles into the PU coating resulted in the blockage of charge transfer at the metal/electrolyte interface, which reduced the dissolution of mild steel. It was revealed from the SEM/EDX analysis that the formation of the corrosion products at the metal/electrolyte interface behaved as the passive layer which reduced the dissolution of steel.
Originality/value
The inclusion of polybenzoxazine functionalized ZrO2 nanoparticles to the polyurethane coating reinforces the barrier and mechanical properties of PU-Pbz/ZrO2 nanocomposite, which is due to the synergistic effect of ZrO2 and Pbz.
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Zhaopeng Wang, Yi Wang, Bowei Zhang, Zhan Zhang, Kui Xiao, Junsheng Wu, Qiong Yao, Guojia Ma and Gang Sun
The purpose of this paper is to investigate the influence of the potential of hydrogen (pH) and dissolved oxygen in artificial seawater on the passivation behavior of 316L…
Abstract
Purpose
The purpose of this paper is to investigate the influence of the potential of hydrogen (pH) and dissolved oxygen in artificial seawater on the passivation behavior of 316L stainless steel.
Design/methodology/approach
The corrosion behavior was studied by using electrochemical measurements such as electrochemical impedance spectroscopy and polarization curve. The passive films were characterized with X-ray photoelectron spectroscopy.
Findings
The polarization resistance of the passive film decreases as the pH value drops ascribed to the formation of much more point defects. The donor carrier concentration (ND) in the passive film formed in the deaerated condition is lower than that in aerated conditions. Nevertheless, this phenomenon is the opposite when the pH value is 1 due to the significant decrease of Fe oxides/hydroxides coupled with the stable content of Cr oxides/hydroxides species. In addition, the compositional variation of the passive film also leads to the changes of its semiconductor properties from N-type to bipolar type.
Originality/value
This paper shows the variation of polarization resistance, corrosion potential, passive film composition and semiconductor properties with the pH value and dissolved oxygen. The results can serve as references to the further study on crevice corrosion of 316L in seawater.
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J. González‐Sánchez, L. Dzib‐Pérez, E. Garcia‐Ochoa, G. Canto and M. Sosa‐Baz
The purpose of this paper is to quantitatively assess the pit growth rate on AISI 304L and AISI 316 austenitic stainless steels in natural seawater and 3.5 wt.% NaCl solutions…
Abstract
Purpose
The purpose of this paper is to quantitatively assess the pit growth rate on AISI 304L and AISI 316 austenitic stainless steels in natural seawater and 3.5 wt.% NaCl solutions through electrochemical measurements during the potentiostatic growth of pits.
Design/methodology/approach
A quantitative characterisation was carried out based on chronoamperometric measurements. The volume of dissolved metal per pit was calculated from the charge registered and Faraday's law, considering both, hemispherical and semi‐elliptical pit shapes and the density of the steels. Empirical growth laws for maximum pit depth as a function of polarisation time were obtained and compared with pits volumetric profile obtained from optical microscopy analysis and mechanical removal of material on both steels.
Findings
Electrochemical‐based calculations of localised metal dissolution per pit present acceptable fit with the real volume of dissolved metal on hemispherical pits.
Originality/value
The paper presents the quantitative relationship of the corrosion pit growth rate of stainless steels in chloride containing solution determined by chronoamperometry (electrochemical technique) through the Faraday law's, with the mechanical removal of material (pit profile) through the density of metal.
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Jiayuan Hu, Shunan Cao, Li Yin, Qinqin Liang and Jianli Xie
Some power plants in China that adopt reverse osmosis (RO) product water as their fresh water source face serious metal corrosion of their water distribution system. The corrosion…
Abstract
Purpose
Some power plants in China that adopt reverse osmosis (RO) product water as their fresh water source face serious metal corrosion of their water distribution system. The corrosion process of carbon steel in RO product water is still not clear and there is no suitable anti‐corrosion method for the power plant to employ. The purpose of this paper is to study the corrosion behavior of carbon steel in RO product water, determine the factors leading to the high corrosion rate of carbon steel, and then suggest appropriate anti‐corrosion measures.
Design/methodology/approach
By measuring polarization curves and AC impedance values of the corrosion system and analyzing corrosion products using scanning electron microscopy (SEM), infrared spectroscopy (IR) and X‐ray diffraction (XRD), the corrosion behavior of Q235A carbon steel in the RO product water derived from seawater was studied.
Findings
The experimental results showed that the corrosion process of carbon steel in RO product water is controlled by the diffusion process of oxygen, and the corrosion products contain γ‐FeOOH, Fe3O4 and small amounts of α‐FeOOH. Although rust formed had a double layer structure, the outer rust layer, which contained γ‐FeOOH and a little α‐FeOOH, was thin. The inner rust layer, containing Fe3O4, was the main component of the rust layer. Due to the weak acidity of RO product water, γ‐FeOOH can be transformed to Fe3O4 very quickly and Fe3O4 will accumulate on the metal surface. Because of the electrical conductivity and fractured surface of the Fe3O4 layer, the corrosion product layer cannot inhibit the corrosion process by hindering the diffusion process of oxygen, and hence the corrosion rate of carbon steel is always high.
Originality/value
The paper describes the first systematic research to be carried out on the corrosion behavior of carbon steel in RO product water. It was found that the generation and accumulation of Fe3O4 on the metal surface was the primary reason leading to the high corrosion rate of carbon steel, and anti‐corrosion measures can be chosen following the following rules: deoxygenation, raising of the pH of the solution, or addition of corrosion inhibitors to the solution.
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This study aims is to evaluate the environmentally friendly turmeric as a corrosion inhibitor for mild steel in a simulated seawater corrosion medium such as a 3.5% NaCl solution…
Abstract
Purpose
This study aims is to evaluate the environmentally friendly turmeric as a corrosion inhibitor for mild steel in a simulated seawater corrosion medium such as a 3.5% NaCl solution. To accomplish this, different proportions of turmeric (0.3, 0.6, 0.9 and 1.5%) were added to solvent-free epoxy-acrylate resin-based coating formulations. Then, all the formulations were sonicated and coated as thin films on different substrates; these coated films were then polymerized under a dose of 10 kGy of electron beam (EB) radiation.
Design/methodology/approach
Various properties of all cured coating films such as Fourier transform infrared spectroscopy, water contact angle, thermogravimetric analysis and scanning electron microscopy were studied, in addition to their physical, chemical and mechanical properties. Turmeric was then evaluated in these formulations as an anticorrosion agent for mild steel in 3.5% NaCl. The different corrosion-resistant properties of all EB-cured coating films were evaluated by open circuit potential measurements, rust degree, blistering, adhesion loss at X-cut and weight loss measurements.
Findings
The results showed that most of the formulations are homogeneous, especially at low concentrations of turmeric, and their films have high-performance properties.
Originality/value
It was also found that the formulation containing 0.6% of turmeric per 100 g of coating was considered the best formulation as it gave the highest protection to the mild steel plates with no negative effects on the chemical and physical properties of their films.
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