Showing papers in "Corrosion Engineering Science and Technology in 2011"
TL;DR: In this paper, a nonlinear function of time is used as the reference corrosion model calibrated with operational corrosion data at long term average conditions to represent the corrosion behavior under standard environmental conditions.
Abstract: This study considers different environmental factors affecting corrosion under marine immersion conditions and proposes a mathematical model incorporating their effects on corrosion degradation through the ship life. The study adopts a nonlinear function of time as the reference corrosion model calibrated with operational corrosion data at long term average conditions to represent the corrosion behaviour under standard environmental conditions. Based on previously obtained field data, a corrosion deterioration model is developed, in which a correction factor is proposed to account for the effect of each environmental factor. These multiplicative factors correct the standard prediction of corrosion degradation to obtain short term estimates under any specific environmental condition. Then, a long term estimate of corrosion degradation is determined by summing the short term corrosion contributions during the various discrete time periods in which the ship life can be decomposed. A numerical example of a representative application of the new empirical based corrosion model is presented, to demonstrate how to apply the model.
92 citations
TL;DR: A method for extracting the key kinetic parameters from radiographs is under development to provide data for validating and calibrating a two-dimensional finite element model previously developed by Laycock and White as mentioned in this paper.
Abstract: In situ synchrotron radiography has been used to observe the evolution of two-dimensional pits growing in stainless steel foils under electrochemical control in chloride solutions. A method for extracting the key kinetic parameters from radiographs is under development to provide data for validating and calibrating a two-dimensional finite element model previously developed by Laycock and White. The local current density along the boundary of a pit is directly measured from the radiographs. Then, the local metal ion concentration and potential drop inside the pit cavity are backcalculated using transport equations and the requirement to maintain charge neutrality, giving the relationship between current density, solution composition and interfacial potential. Preliminary comparisons show qualitative correlation between the model and extracted data; quantitative comparison is under way.
47 citations
TL;DR: In this article, a 25·5 km long and 28 in. diameter underground pipeline used for transporting wet sour Arab Light grade crude oil failed after 3 years of service due to corrosion of the lower surface of the pipeline.
Abstract: A 25·5 km long and 28 in. diameter underground pipeline used for transporting wet sour Arab Light grade crude oil failed after 3 years of service. The pipeline was operated at 40% of permissible flow velocity and capacity and protected under a corrosion inhibitor programme. The failure occurred due to corrosion of the lower surface of the pipeline resulting in pinholes within a period of one month. Eight corrosion damaged areas were detected over the entire length of the pipeline. Ultrasonic non-destructive inspection and close potential surveys were conducted on the failed pipeline. Various sections of the corrosion products were metallurgically evaluated using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The corrosion product was identified using photometric and potentiometric analysis combined with X-ray diffraction. Crude oil and water samples obtained from the pipeline were also analysed. The material of the pipeline was identified as AISI grade C1018. Ultra...
41 citations
TL;DR: In this paper, the effect of chloride deposition on the susceptibility to atmospherically induced stress corrosion cracking (AISCC) of stainless steel type AISI 316L used to manufacture containers for radioactive intermediate level waste in the UK was analyzed.
Abstract: This work analysed the effect of chloride deposition on the susceptibility to atmospherically induced stress corrosion cracking (AISCC) of stainless steel type AISI 316L used to manufacture containers for radioactive intermediate level waste in the UK. Using U-bend specimens contaminated with MgCl2, a threshold deposition for AISCC occurrence has been found above chloride contamination levels of 10 and 25 μg cm−2 at 50 and 30°C respectively at the equilibrium relative humidity (RH) of the contaminant salt (∼30%RH). Higher contamination levels were required to produce cracking at 60%RH. Based on crack depth data and contaminated area characterisation, it was found that susceptibility to AISCC is affected by the liquid film volume, thickness and continuity.
40 citations
TL;DR: In this paper, the long term corrosion behavior of copper in anoxic aqueous sulphide solutions has been studied using corrosion potential and electrochemical impedance spectroscopy measurements and scanning electron microscopy on corroded surfaces and cross-sections of surfaces prepared using a focused ion beam.
Abstract: The long term corrosion behaviour of copper in anoxic aqueous sulphide solutions has been studied using corrosion potential and electrochemical impedance spectroscopy measurements and scanning electron microscopy on corroded surfaces and cross-sections of surfaces prepared using a focused ion beam. Experiments were conducted in solutions containing either 5×10−4 or 5×10−5 mol L−1 sulphide for 1691 and 4000 h respectively. In the more concentrated solution, a coherent, compact and crystalline chalcocite (Cu2S) film accumulated on the corroding copper surface. A parabolic growth law was obtained, and the kinetics were controlled by Cu(I) ion transport either through the Cu2S matrix or along crystalline grain boundaries in the film. In the more dilute solution, the growth of a less crystalline, porous chalcocite layer followed approximately the linear growth kinetics controlled by sulphide ion transport through the pores. If the sulphide was allowed to deplete in the dilute solution, rate control swi...
38 citations
TL;DR: A review of the corrosion performance of selected canister materials for the disposal of high activity waste in the UK is presented in this article, where the advantages and disadvantages of each material are described, as are limiting or "critical" conditions for which the use of a given material is questionable or not recommended.
Abstract: A review of the corrosion performance of selected canister materials for the disposal of high activity waste in the UK is presented. The canister materials considered are carbon steel, copper, stainless steels, titanium alloys and nickel alloys. The purpose of the review is to provide a high level overview of the technical and scientific issues relating to the use of each of these materials for the disposal of high level waste and spent nuclear fuel in the UK. The advantages and disadvantages of each material are described, as are limiting or ‘critical’ conditions for which the use of a given material is questionable or not recommended.
37 citations
TL;DR: The Swedish Nuclear Fuel and Waste Management Company has developed a method for safely disposing spent nuclear fuel, which involves encapsulation of the waste in copper canisters and burying it deep in the stable crystalline rock of the Fenno-Scandian shield as mentioned in this paper.
Abstract: The Swedish Nuclear Fuel and Waste Management Company has developed a method for safely disposing spent nuclear fuel, which involves encapsulation of the waste in copper canisters and burying it deep in the stable crystalline rock of the Fenno-Scandian shield. The design life of the canisters in the so called KBS-3 design is in excess of 100 000 years. These long canister lifetimes are a consequence of a number of factors involving the properties of the material and the nature of the near field environment in the KBS-3 repository. One of these factors, namely the thermodynamic stability of copper in O2 free water in the absence of sulphide, has been questioned. This paper critically reviews the evidence for and against the claim that water oxidises copper, and discusses the implications for canister lifetimes even if the proposed mechanism is correct. Even though the evidence presented in support of the proposed mechanism is not compelling, the Swedish Nuclear Fuel and Waste Management Company is ...
36 citations
TL;DR: In this article, the effect of microstructure change on industrial pure Al was investigated by optical/electron microscopy observation, constant immersion tests, polarisation tests and electrochemical impedance spectroscopy (EIS) in aqueous NaCl solution.
Abstract: Significant grain refinement and corrosion resistance improvement were achieved in industrial pure Al through equal channel angular pressing (ECAP). The effect of microstructure change on its corrosion resistance was investigated by optical/electron microscopy observation, constant immersion tests, polarisation tests and electrochemical impedance spectroscopy (EIS) in aqueous NaCl solution. The ultrafine grained (UFG) bulk pure Al (with grain sizes of 300–500 nm) has a higher pitting potential Epit, a lower corrosion current density Icorr in polarisation tests and an increased polarisation resistance Rp from EIS plots, along with reduced corrosion damage in immersion tests, compared with the as cast material. It was found that the improved corrosion resistance resulted from the uniform distribution of fine Si containing impurities and the formation of a denser oxide film. The ECAPed samples with smaller Si containing impurities have lower microgalvanic currents and reduced susceptibilities of pitt...
34 citations
TL;DR: In this article, the authors compared different electrochemical methods for determining the repassivation potential of Alloy 22 (UNS N06022), including cyclic potentiodynamic polarisation, Tsujikawa-Hisamatsu electrochemical, potentiodynamics-galvanostatic-potentiodynamic (PGPG-GOP) method, and PTFE-wrapped ceramic crevice formers.
Abstract: Alloy 22 (UNS N06022) belongs to the Ni–Cr–Mo family, and it is highly resistant to general and localised corrosion; however, it may suffer crevice corrosion in aggressive environmental conditions. The susceptibility to crevice corrosion is measured by the value of the repassivation potential. The objective of this work is to compare different electrochemical methods for determining the repassivation potential of alloy 22; these include cyclic potentiodynamic polarisation, Tsujikawa–Hisamatsu electrochemical, potentiodynamic–potentiostatic–potentiodynamic and potentiodynamic–galvanostatic–potentiodynamic methods. The potentiodynamic–galvanostatic–potentiodynamic technique was found to be the most conservative laboratory technique, which gave the lowest repassivation potential in a relatively short testing time. The polytetrafluoroethylene (PTFE)-wrapped ceramic crevice formers formed more severe crevices, leading to higher repassivation potentials than the solid PTFE crevice formers. Torque values higher ...
33 citations
TL;DR: In this article, a reactive transport model was developed to predict the evolution of the general corrosion behavior of the copper canisters by the initially trapped O2 and by sulphide ions, including the microbial reduction of sulphate, the dissolution of pyrite impurities and the ground water itself.
Abstract: The well known KBS-3 repository design involves the disposal of spent fuel in copper canisters in a deep geological repository sealed with clay based buffer and backfill materials. A one-dimensional reactive transport model has been developed to predict the evolution of the general corrosion behaviour of the copper canisters by the initially trapped O2 and by sulphide ions. Various sources of sulphide are considered, including the microbial reduction of sulphate, the dissolution of pyrite impurities and the ground water itself. The model has been used to simulate the evolution of the canister corrosion behaviour for various scenarios, including both the Olkiluoto and Forsmark proposed repository locations, the vertical and horizontal KBS-3 design variants, increased ground water sulphide or chloride concentrations, different microbial scenarios, different rates of repository saturation, and with and without the dissolution of pyrite. Following a brief description of the model, the results of these...
32 citations
TL;DR: In this article, the status of the RD&D program related to the anaerobic uniform corrosion of the carbon steel overpack is discussed. But the authors focus on the non-uniform corrosion mechanisms (e.g., pitting corrosion, crevice corrosion and stress corrosion cracking).
Abstract: The Supercontainer design is the preferred option for the underground disposal of high level nuclear waste in Belgium. It consists of a carbon steel overpack surrounded by a thick concrete buffer. In this high alkaline environment and under normal conditions (without the ingress of aggressive species), the carbon steel overpack will be protected by a passive oxide film, which is believed to result in very low uniform corrosion rates. The backbone of the RD&D strategy, which aims to provide confidence that the integrity of the overpack will be maintained at least during the thermal phase, is based on demonstrating that each localised corrosion mechanism (e.g. pitting corrosion, crevice corrosion and stress corrosion cracking), other than uniform corrosion, cannot take place under the high pH conditions prevailing within the Supercontainer (the ‘exclusion principle’). This paper gives an overview of the status of the RD&D programme related to the anaerobic uniform corrosion of the carbon steel overp...
TL;DR: In this article, the transformation of rust in the presence of 5 g L−1 tannins extracted from mangrove (Rhizophora apiculata) barks was studied.
Abstract: Rust converters are chemical formulations that can be applied to corroded surfaces to convert residual rust on iron/steel surfaces into harmless and adherent chemical compounds. The known hazardous effects of most synthetic rust converters have led to a search for safer, more environmentally friendly natural products. Tannins, a class of natural, non-toxic and biodegradable polyphenolic compounds, extracted from plant sources have been proposed as an alternative. The transformation of rust in the presence of 5 g L−1 tannins extracted from mangrove (Rhizophora apiculata) barks was studied. Three different methods of pre-rusted sample preparations were tested. The rust composition of the steel was dependent of sample preparation. The pre-rusted samples prepared formed predominantly lepidocrocite and magnetite. Transformation of rust components to ferric-tannates, particularly lepidocrocite, in the presence of mangrove tannins that could be observed via Fourier transform infrared spectroscopy, X-ray ...
TL;DR: In this paper, a rotating cylinder electrode apparatus was designed so that electrodes machined from the weld metal, heat affected zone and parent material of welded X65 pipeline steel could be galvanically coupled and tested in high shear stress conditions.
Abstract: The aim of this research was to investigate the cause of the severe localised corrosion that sometimes occurs at welds in carbon steel pipelines carrying hydrocarbons and inhibited brines saturated with carbon dioxide. A rotating cylinder electrode apparatus was designed so that electrodes machined from the weld metal, heat affected zone and parent material of welded X65 pipeline steel could be galvanically coupled and tested in high shear stress conditions. The galvanic currents flowing between the weld regions were recorded using zero resistance ammeters, and their self-corrosion rates were found by polarisation resistance measurements. The total corrosion rate of each weld region was obtained from the sum of the self-corrosion and galvanic contributions. In uninhibited conditions, the weld metal and heat affected zone were both cathodic to the parent material, and localised corrosion was prevented. However, when an oilfield corrosion inhibitor was present, a current reversal took place, which resulted in accelerated weld corrosion. Electrochemical impedance spectroscopy showed that the inhibitor film had lower electrical resistance and was less protective on the weld metal than on the parent material. At the highest shear stress, a second current reversal could occur when the inhibitor was removed from all regions of the weld, and there was a return to the original galvanic behaviour. It was concluded that preferential weld corrosion was caused by unstable conditions in which the inhibitor film was selectively disrupted on the weld metal but remained effective on the other weld regions.
TL;DR: In this paper, an experimental research was performed on both mixed and migrating inhibitors to prevent and control rebar corrosion in concrete, and the ability to delay time to corrosion and to reduce corrosion rate has been studied both in the case of chloride-induced corrosion and carbonated concrete.
Abstract: To prevent and control rebar corrosion in concrete, corrosion inhibitors may be used both as a preventative technique if added to fresh concrete and as a repair system if applied to hardened concrete. In the past six years, an experimental research was performed on both mixed and migrating inhibitors. Effectiveness of mixed inhibitors has been investigated in Part 1: the ability to delay time to corrosion and to reduce corrosion rate has been studied both in the case of chloride-induced corrosion and carbonated concrete. Organic migrating inhibitors were applied to concrete specimens, and their ability to control corrosion was investigated: results are described in Part 2. Results allow to state that the inhibitors are able to delay time to corrosion, while a negligible effect was observed in the reduction of corrosion rate. In the third part, the inhibitor migration into concrete has been analysed in order to quantify inhibitor penetration depth and main penetration mechanism.
TL;DR: In this article, the influence of postweld heat treatment (PWHT), solution annealing followed by aging at 480, 550 and 620°C on the galvanic corrosion in 17-4PH stainless steel weldment in 3·5%NaCl was studied.
Abstract: The influence of post-weld heat treatment (PWHT), solution annealing followed by aging at 480, 550 and 620°C on the galvanic corrosion in 17-4PH stainless steel weldment in 3·5%NaCl was studied. Potentiodynamic polarisation revealed that all PWHTs improve the passivity of weld region by increasing the pitting potential. Heat affected zone disappears, and base and weld regions act as the anode and the cathode respectively. Zero resistance ammetry measurement for 42 h showed that PWHTs improve the galvanic corrosion resistance by decreasing the galvanic current density to a few to tenths of nanoampere per square centimetre. Aging at 620°C has the highest risk of galvanic corrosion among the three PWHTs. Difference in corrosion characteristic of base and weld were addressed to microstructure variations including ferrite, copper rich precipitates and reverted austenite.
TL;DR: In this paper, an in situ electrochemical probe, utilising anodic stripping voltammetry (ASV), has been developed to measure dissolved Cr concentration in the molten salt LiF-KF-NaF (46·5−11·5-42 mol.-%), commonly referred to as FLiNaK.
Abstract: An in situ electrochemical probe, utilising anodic stripping voltammetry (ASV), has been developed to measure dissolved Cr concentration in the molten salt LiF–KF–NaF (46·5–11·5–42 mol.-%), commonly referred to as FLiNaK. Tests were performed in a glassy carbon crucible in an argon atmosphere glovebox at a molten salt temperature of 650°C. Cyclic voltammetry was performed to determine reversibility and mid peak potential. The Cr2+/Cr0 reaction occurred with a mid peak potential of −0·51 V versus a 10 mol.-% Ni2+/Ni0 reference electrode. The integrated current from the anodic waves at this potential were used for Cr cation quantification. The integrated current from the ASV measurements correlated linearly with Cr concentration, measured independently using neutron activation analysis, over a range of 30–950 ppm (1·2–38 mmol L−1). This study is significant for determining Cr concentrations in high temperature molten FLiNaK salts exposed to Cr containing structural materials.
TL;DR: In this article, the authors focus on the potential measurement problem in the presence of AC through standard potential measurement procedure and the use of a potential probe, and suggest the need of a proper methodology for potential measurement to determine reliably CP conditions.
Abstract: Cathodic protection (CP) monitoring in the presence of simultaneous AC and DC interference could lead to erroneous measurements, since IR drop contribution due to both DC and AC could heavily affect potential readings. Therefore, to know the true potential (or true polarisation level), the ohmic drop contribution has to be eliminated. In literature, there is lack of agreement about the proper procedure to measure the true potential in the presence of AC. Laboratory tests on carbon steel specimens in soil simulating conditions were carried out focusing on potential measurement problem in the presence of AC through standard potential measurement procedure and the use of a potential probe. Results suggest the need of a proper methodology for potential measurement to determine reliably CP conditions.
TL;DR: In this article, the microarc oxidation (MAO) of AM60 magnesium alloy in two kinds of electrolytes is studied to compare the influence of electrolyte on the properties of the MAO coatings.
Abstract: The microarc oxidation (MAO) of AM60 magnesium alloy in two kinds of electrolytes is studied in this paper to compare the influence of electrolytes on the properties of the MAO coatings. One concentrated electrolyte is composed of 100 g L−1 NaOH+20 g L−1 Na2B4O7.10H2O+50 g L−1 C6H5Na3O7.2H2O+60 g L−1 Na2SiO3.9H2O and the other is a dilute solution, which is composed of 5 g L−1 NaOH+15 g L−1 Na2SiO3.9H2O. It was found that the sparking behaviour in dilute electrolyte is more intensive and the breakdown voltage UB is higher (the UB in dilute electrolyte is 282 V, while it is 82 V in the concentrated electrolyte). The thermal effect during the MAO in the two electrolytes is also measured, and the temperature increment in dilute electrolyte is more than twice of that in the concentrated electrolyte. The corrosion resistance of the MAO films is studied by electrochemical impedance spectroscopy and potentiodynamic polarisation techniques and the microstructure of the films is examined by SEM. The electr...
TL;DR: In this article, the corrosion rate of pure copper in an oxic bentonite/saline groundwater environment has been followed by thin electrical resistance sensors placed in a bentonite test package that was kept at room temperature for 3 years.
Abstract: The principal strategy for high level radioactive waste disposal in Sweden is to enclose the spent fuel in copper canisters that are embedded in bentonite clay ∼500 m down in the Swedish bedrock. At this depth, the groundwater is reducing. However, oxic conditions are initially established in the repository during emplacement. The corrosion rate of pure copper in an oxic bentonite/saline groundwater environment has been followed by thin electrical resistance sensors placed in a bentonite test package that was kept at room temperature for 3 years. The corrosion potentials of the sensors have verified oxic conditions in the test package. The corrosion rate of pure copper in this environment has been found to slowly decrease to quite low but measurable values; from above 15 μm/year down to ∼1 μm/year after 3 years of exposure. The measurements have verified a desired behaviour of copper in the environment.
TL;DR: In this paper, the corrosion behavior of carbon steel A106 and stainless steel 304 (SS304) in aqueous monoethanolamine was studied by performing electrochemical polarisation experiments.
Abstract: Corrosion behaviour of carbon steel A106 and stainless steel 304 (SS304) in aqueous monoethanolamine was studied by performing electrochemical polarisation experiments. Potentiodynamic curves were studied and compared under conditions with different temperatures, carbon loading and O2 percentage in purging gases. It was found that corrosion of A106 and SS304 was promoted under conditions with higher temperature. While the presence of O2 speeds the corrosion of A106, it has a negligible impact on SS304 at 80°C and lowers the corrosion rate at 40°C. Corrosion rates and other important parameters were calculated based on the electrochemical curves for A106. Sample surfaces after tests were examined by scanning electron microscopy and energy dispersive spectroscopy. Mechanisms involved in iron dissolution and passivation from oxide films were discussed.
TL;DR: In this paper, the effects of radiation on the anaerobic corrosion of carbon steel, in relation to the overpack that will be used in the Belgian super container concept for radioactive waste disposal, were investigated.
Abstract: This paper summarises recent experimental results from a programme that was carried out to investigate the effects of radiation on the anaerobic corrosion of carbon steel, in relation to the overpack that will be used in the Belgian supercontainer concept for radioactive waste disposal. Anaerobic corrosion rates of carbon steel were measured by monitoring hydrogen evolution using manometric gas cells and an autoclave and the corresponding electrochemical behaviour was investigated by measuring open circuit potential, linear polarisation resistance and alternating current impedance. The test medium was alkaline simulated pore water, at γ-irradiation dose rates of 0 and 25 Gy h−1, temperatures of 25 and 80°C and chloride concentrations of 0 and 100 mg L−1. The anaerobic corrosion rates exhibited a slow decline due to the formation of magnetite. Good agreement was found with weight loss measurements. A dose rate of 25 Gy h−1 had a negligible effect on gas generation rates.
TL;DR: In this paper, the corrosion protection and barrier properties of the sol-gel layer on stainless steel substrate are investigated as a function of the thickness, and the protection conferred by the solgel layer is studied by the electrochemical measurements in a sodium chl...
Abstract: An efficient energy management of a building requires optimum use of the light energy, which is strongly dependent on optical properties of used materials. In the lighting sector, aluminium is generally employed as substrate for the reflectors. Nowadays, new steel substrates combining good corrosion resistance and flexibility are developed to answer the growing need of this market. Specific requirements for optical applications are a high reflectivity (total reflectivity >82%), a high superficial hardness and durability and also a suitable formability. The sol–gel layer is used in this particular application for its levelling properties before depositing of the reflective layer and good barrier properties to avoid contact between the metallic layers. The corrosion protection and the barrier properties of the sol–gel layer are investigated as a function of the thickness. The protection conferred by the sol–gel layer on stainless steel substrate is studied by the electrochemical measurements in a sodium chl...
TL;DR: In this paper, the effect of PEO coatings on the stress corrosion cracking (SCC) behavior of the alloy was investigated by slow strain rate tensile (SSRT) tests in ASTM D1384 solution.
Abstract: A wrought AZ31 magnesium alloy was plasma electrolytic oxidation (PEO) coated in phosphate and silicate based alkaline electrolytes The effect of these PEO coatings on the stress corrosion cracking (SCC) behaviour of the alloy was investigated by slow strain rate tensile (SSRT) tests in ASTM D1384 solution The untreated and PEO coated AZ31 magnesium alloy specimens were found to be susceptible to SCC, despite the fact that the PEO coatings offered an excellent general corrosion resistance The results of the polarisation tests on the untreated AZ31 alloy specimen after prolonged immersion in ASTM D1384 electrolyte suggested the formation of a film on the surface constituted by the corrosion products The cracking of this film and the evolution/ingress of hydrogen at these defective sites during the SSRT tests in the corrosive environment was believed to be responsible for the SCC of the untreated alloy Similarly, the cracking of the PEO coatings during the SSRT test, the consequent exposure of the unde
TL;DR: In this article, the authors examined the corrosion properties of duplex treated (nitrided and with a diamond-like carbon coating) 316L stainless steel and Ti-6Al-4V alloy.
Abstract: 316L and Ti–6Al–4V are widely used as biomaterials and materials of various mechanical components. In biomedical applications, they are used to manufacture coronary and pulmonary stents, hip prosthesis, screws and external fixations. However, Cr, Al and V are released from the alloys to the body environment and these ions mix into the blood stream. Release of even small amounts of these ions may cause local irritation of the tissues surrounding the implant. This situation may be prevented by applying suitable surface treatments to the biomaterials. The overall objective of the present paper is to examine the corrosion properties of duplex treated (nitrided and with a diamond-like carbon coating) 316L stainless steel and Ti–6Al–4V alloy. Diamond-like carbon films were deposited on nitrided samples using closed field unbalanced magnetron sputtering system. The corrosion behaviour of duplex treated samples was tested using the potentiodynamic method in ringer’s solution at 37uC. The corrosion resistance of duplex treated samples was significantly improved in comparison with the uncoated and single treated samples. In addition, the corroded surfaces were investigated by SEM where small pits were observed on all samples.
TL;DR: In this paper, the corrosion performance of untreated, direct current and active screen plasma carburised AISI 316 was investigated by immersion in a boiling solution of sulphuric acid, and the experimental results showed that the corrosion behaviour of expanded austenite produced by low temperature plasmaCarburising is controlled by the type and density of surface defects.
Abstract: Active screen plasma is a recently developed plasma surface alloying technique, which has shown potential for addressing some drawbacks associated with conventional direct current plasma processes. In this study, the corrosion performance of untreated, direct current and active screen plasma carburised AISI 316 was investigated by immersion in a boiling solution of sulphuric acid. The experimental results show that the corrosion behaviour of expanded austenite produced by low temperature plasma carburising is controlled by the type and density of surface defects; the corrosion properties of the active screen plasma carburised material are superior to that produced by direct current plasma because of the significantly reduced edge effect and surface defects; and the bias level used in the active screen carburising treatment has a profound effect on the corrosion performance of the material. Based on the experimental results, the corrosion mechanisms involved are discussed.
TL;DR: In this paper, the authors investigated the hydrogen permeation behavior of X56 steel under loading in a simulated atmospheric environment and found that the hydrogen percolation current increases as the elastic deformation of the steel increases.
Abstract: The hydrogen permeation behaviour of X56 steel under loading in a simulated atmospheric environment was investigated. The results show that the hydrogen permeation current increases as the elastic deformation of the steel increases. In addition, the hydrogen permeation current decreases with an increase in plastic deformation. Cracking of the passive film and the reduced specimen thickness after deformation are proposed as reasons for the decrease in permeation. Thus, during plastic deformation, there is a competition between dislocation trapping and dislocation transport of hydrogen, which affects the overall hydrogen permeation current.
TL;DR: In this paper, a metal waste form (MWF) alloy of D9 stainless steel with 8·5 wt% zirconium was cast and evaluated for the corrosion behaviour.
Abstract: Metal waste form (MWF) alloy of D9 stainless steel with 8·5 wt-% zirconium was cast and evaluated for the corrosion behaviour. The microstructure, phase analysis, corrosion resistance and passive film properties of the alloy were evaluated using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and electrochemical methods. The corrosion performance of MWF alloy was carried out in demineralised (DM) water at pH 1, 5 and 8 and also in simulated Kalpakkam and Rajasthan ground water systems. In X-ray diffraction analysis, the identified phases are mostly iron based solid solutions of γ-austenite, Zr–Fe type and Ni–Zr type intermetallics. The typical microstructure of MWF alloy showed the presence of solid solution and the intermetallics. The anodic polarisation results of MWF alloy in Rajasthan ground water and in DM water at pH 5 and 8 showed higher breakdown potential compared with DM water at pH 1 and in Kalpakkam ground water. The electrochemical impedance spectroscopic...
TL;DR: In this article, the dependence of the corrosion rate on cell current density (CD) for three anode materials (Pb-Ca-Sn, RuO2-IrO2/Ti and IrO2−Ta2O5/Ti) in a laboratory scale copper electrowinning cell has been studied by means of short term weight loss tests, scanning electron microscopy observations and energy dispersive spectroscopy analysis.
Abstract: The dependence of the corrosion rate on cell current density (CD) for three anode materials (Pb–Ca–Sn, RuO2–IrO2/Ti and IrO2–Ta2O5/Ti) in a laboratory scale copper electrowinning cell has been studied by means of short term weight loss tests, scanning electron microscopy observations and energy dispersive spectroscopy analysis. The lead anodes (Pb–Ca–Sn) corroded at all the studied cell CDs, and their corrosion rate increased with increasing cell CD. The precious metal oxide anodes (RuO2–IrO2 and IrO2–Ta2O5) only exhibited corrosion at the highest tested cell CD (1000 A m−2), and their corrosion rates were about a quarter of the lead corrosion rate at the same cell CD. The electrocatalytic properties of the three anode materials were characterised by means of potentiodynamic experiments. The overall results pointed to IrO2–Ta2O5/Ti as the best anode material of choice, although plant tests would be required before deciding on any specific commercial use.
TL;DR: In this paper, a set of model canisters was set up in the Aspo underground laboratory in contact with bentonite with a range of densities, and water analysis and electrochemical measurements indicated an increase in the corrosion rate of both iron and copper.
Abstract: To ensure the safe disposal of spent fuel in Sweden, SKB is planning to use the copper–iron canister in a granitic deep geological repository, surrounded by a compacted bentonite engineered barrier. In order to develop a deeper understanding of the internal corrosion behaviour of the design should a leak occur in the outer copper canister, a set of model canisters was set up in the Aspo underground laboratory in contact with bentonite with a range of densities. The environmental conditions and electrochemical corrosion behaviour were monitored using a range of techniques. Water analysis and electrochemical measurements indicated an increase in the corrosion rate of both iron and copper in contact with low density bentonite, and of iron only in experiments with no bentonite present. This behaviour may be attributable to microbial activity. The measured corrosion rate depends on the technique used and it will be necessary to confirm the measurements by removal and examination of weight loss coupons.
TL;DR: In this article, the performance of nanocrystalline Zn-Ni alloy coatings with 3 to 18 at-%Ni was investigated by measurement of open circuit potential with time and neutral salt spray test.
Abstract: Corrosion behaviour of nanocrystalline Zn–Ni alloy coatings (with 3 to 18 at-%Ni) electrodeposited on steel substrate from additive free chloride baths by DC plating has been investigated by measurement of open circuit potential with time and neutral salt spray test. The alloy coatings containing up to 16 at-%Ni exhibited an increase in resistance to the appearance of white and red rust with increasing Ni content. The resistance to the appearance of white rust and ability to protect the underlying steel substrate decreased with further increasing Ni content. This has been considered to be due to reduced passivating ability of the alloy coating with a significant rise in the grain size above 50 nm.