Aspects Of Corrosion Research Articles

In‐vitro evaluation of the corrosion behavior of orthodontic brackets

The number of bracket systems for orthodontic therapy increases significantly. One major concern of newly developed orthodontic devices is aspects of corrosion and biocompatibility. In this study, nine bracket systems made of different material and from various design principles were tested with respect to their corrosion behavior. Electrochemical and static immersion tests with subsequent measurement of nickel ion release were performed. In addition surface alterations of the brackets after corrosion were documented by scanning electron microscopy. Studies of corrosion behavior were performed according to the DIN/ISO standard 10271 for corrosion testing of dental materials. All systems showed traces of corrosion after electrochemical testing. However, after static immersion testing only minor corrosion defects could be documented and the measured nickel ion release was far below critical limits. All tested systems seem to be biocompatible and applicable for orthodontic therapy. The measured nickel values are far below the daily dietary intake level. A static immersion test combined with the nickel ion release measurement seems to be more relevant for the determination of biocompatibility than the electrochemical testing.

An overview of the corrosion aspect of dental implants (titanium and its alloys)

Titanium and its alloys are used in dentistry for implants because of its unique combination of chemical, physical, and biological properties. They are used in dentistry in cast and wrought form. The long term presence of corrosion reaction products and ongoing corrosion lead to fractures of the alloy-abutment interface, abutment, or implant body. The combination of stress, corrosion, and bacteria contribute to implant failure. This article highlights a review of the various aspects of corrosion and biocompatibility of dental titanium implants as well as suprastructures. This knowledge will also be helpful in exploring possible research strategies for probing the biological properties of materials.

Electrochemical and Erosion Corrosion Aspect on Main Gas Pipe Line in Sinter Plant: for Raw Petroleum Coke as Trimming Fuel

Different corrosion mechanisms and their extent within a sinter plant gas pipeline were studied. The low temperature-high moisture at the charging side and high temperature-low moisture at the discharging side exist in the main gas pipeline. The waste gas velocity is maximum near charging side and minimum near discharging side. Aggressive conditions near the charging side resulted in faster corrosion than the discharging side. The electrochemical effect was predominant at the wall while erosion effect was significantly higher at the center of the pipe. The overall effect however turns out to be same at wall and center for a particular location of the pipeline. This has been attributed to the velocity effect of waste gases.The corrosion products were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction XRD techniques. The low temperature-high moisture at the charging side promotes electrochemical reaction with formation of bigger goethite and hematite. Only, hematite was detected in between charging and discharging side where as different iron oxides and alkali compounds were detected near the discharging side.

Some aspects of copper corrosion in presence of benzotriazole and chloride ions

This paper deals with the investigation of electrochemical behaviour of copper in a sodium tetraborate (borax) solution in the presence and absence of chloride ions. The influence of benzotriazole (BTA) on the anodic behaviour of copper was also investigated. It was found that Cu 2O and CuO oxides were formed on copper and that peak current moved to the positive side with increased immersion time in a sodium tetraborate solution. After 1 h immersion of the copper electrode in a sodium tetraborate solution containing various chloride ion concentrations (0.001, 0.010, 0.050, and 0.100 mol/dm 3 Cl −) the activation effect of those ions was found, whereas after 6 h immersion of copper in the above mentioned solutions, chloride ions were found to have not only activation but also passivation effect. The investigation of the effect of benzotriazole led to a conclusion that BTA has an inhibiting effect with increasing immersion times (15 min, 1 h, 4 h, and 48 h) as well as with increasing BTA concentrations (8.4 × 10 −6, 8.4 × 10 −5, 8.4 × 10 −4, and 8.4 × 10 −3 mol/dm 3). In addition, at the lowest investigated BTA concentration (8.4 × 10 −7 mol/dm 3) an activation effect of this compound on copper dissolution was observed. Based on the Langmuir adsorption isotherm, the value of the standard free energy adsorption was found to be Δ G 0 = −35.4 kJ/mol.

Microstructural, tribological and corrosion aspects of thermally sprayed Ti–Cr–Si coatings

This paper is a first report of thermally sprayed Ti 60Cr 32Si 8 (at.%) alloy coating. It has been reported previously that such an alloy assumes quasicrystallinity in the presence of oxygen, when made to undergo rapid quenching. In these cases, either TiO or SiO 2 is used as an ingredient in the alloy so that it can act as a source of oxygen. This paper describes an attempt to produce a quasicrystal by thermally spraying the alloy in air, i.e., in the presence of oxygen, either by flame or atmospheric plasma spraying. The spray parameters for both the processes have been varied in the experiment in a wide range. A vacuum plasma sprayed coating served as the reference. This investigation includes a detailed study of the microstructure and phases by optical microscopy, Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), microhardness and porosity. An estimate of the composition of the coating has been done using Glow Discharge Optical Emission Spectroscopy (GDOES).The parametric variations have been correlated with the coating microstructure. The tribological properties of these coatings were studied using a ball on disc reciprocating tribometer. The corrosion properties of one representative coating have been studied using potentio-dynamic method and the corrosion response has been correlated with the microstructure. It has been found in the study that there is a likelihood of obtaining quasicrystal by atmospheric plasma spraying of this alloy under favorable parametric conditions. Some of the coatings produced in this study have very good wear resistance. The corrosion property of the coating under study has been dominated by microcracks. During corrosion testing the corroding media has been found to percolate through these cracks and attack the substrate.

Mechanistic aspects of electrochemical corrosion of aluminum alloy in ethylene glycol–water solution

The electrochemical corrosion behavior of 3003 aluminum (Al) alloy in ethylene glycol–water solutions was studied by electrochemical measurements and surface analysis techniques through an impingement jet system. Al corrosion in aerated, stationary solution is a mixed-controlled process, i.e., both activation and mass-transfer steps control the corrosion reaction. Upon flowing of solution, no matter if sand particles are contained, Al corrosion is an activation-controlled process. In addition to Al oxide film, a layer of Al-alcohol film will also be formed on the electrode surface in ethylene glycol–water solution, contributing to inhibition of anodic dissolution of Al. In the absence of oxygen, a stable passivity could also be achieved on Al alloy. The main cathodic reaction is either reduction of water or reduction of ethylene glycol. However, the reduction of water and ethylene glycol would not be as significant as that of oxygen. As a consequence, the resultant film is not as stable as that formed in the presence of oxygen, as shown in polarization measurements. Al corrosion reaction in mixed-controlled by activation step and mass-transfer step through the anodic surface film. The coverage of the adsorbed intermediate product on Al electrode surface is expected to be very small under the impingement of fluid and sand particles, which results in the generation of an inductive loop in Nyquist diagrams measured on Al electrode in ethylene glycol–water solution.

Influence of oxygen ion irradiation on the corrosion aspects of Ti-5%Ta-2%Nb alloy and oxide coated titanium

The corrosion resistance of Ti-5%Ta-2%Nb alloy and DOCTOR (double oxide coating on titanium for reconditioning) coated titanium by O 5+ ion irradiation were compared and investigated for their corrosion behaviour. O 5+ ion irradiations were carried out at a dose rate of 1 × 10 17, 1 × 10 18 and 1 × 10 19 ions/m 2 at 116 MeV. The surface properties and corrosion resistance were evaluated by using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray (EDX), glancing-angle X-ray diffraction (GXRD) and electrochemical testing methods. The results of electrochemical investigations in 11.5 N HNO 3 indicated that the open circuit potential (OCP) of DOCTOR coated titanium is nobler than Ti-5%Ta-2%Nb alloy. The potentiodynamic polarization study of Ti-5%Ta-2%Nb alloy and DOCTOR coated specimen indicated decrease in passive current density with increase in ion doses (1 × 10 17 to 1 × 10 19 ions/m 2) indicating decrease in anodic dissolution. Nyquist arc behaviour in the electrochemical impedance study substantiated the enhancement in oxide layer stability by O 5+ ion irradiation. AFM results revealed that the DOCTOR coated Ti surface was dense without gross voids, and the surface roughness decreased by O 5+ ion irradiation, but increased after corrosion test. EDX and GXRD patterns of DOCTOR coated Ti sample indicated that the coating was mainly composed of rutile TiO 2. Based on the above results, the O 5+ ion irradiation effect on corrosion behavior of Ti-5%Ta-2%Nb alloy and DOCTOR coated titanium are discussed in this paper.

Measurement of Corrosion Potentials of the Internal Surface of Operating High-Pressure Oil and Gas Pipelines

Abstract Corrosion potential is a fundamental electrochemical parameter critical to understanding the thermodynamic aspects of corrosion. Many corrosion theories are based on corrosion potentials. Corrosion potential is routinely and easily measured in the laboratory. In order to transfer this scientific knowledge from the laboratory to the field, it is necessary to determine the corrosion potential under operating field conditions. In this paper, the unique challenges measuring corrosion potentials in an industrial environment are described using measurements of the corrosion potentials of the internal surfaces of pipelines as examples.

Some aspects of plant corrosion and protection in oil refining

Some aspects of plant corrosion and protection in oil refining

Hierarchical Bayes methods for systems with spatially varying condition states

In engineering decision making, we often face problems where the conditions governing certain response models vary spatially. In such cases, the use of hierarchical Bayesian models is often beneficial. Such models are based on a “condition state” vector that is assumed to be conditionally independent given a set of “hyper-parameters.” All other process parameters are then conditional on this state variable vector. Such models can be applied to a large variety of problems where data from various systems or sources need to be spatially “mixed,” such as in deteriorating infrastructure, spatial aspects of corrosion, preference and consequence modeling, and system failure models for large industrial plants. The models are especially useful for performing statistical inference and for updating in the context of life-cycle optimization, optimal inspection, and maintenance planning. A detailed extension is explored that allows for the spatial correlation of the individual “states” given the hyper-parameters. This allows an efficient posterior assessment of high-level upcrossing rates for the purpose of risk analysis.Key words: spatially distributed processes, hierarchical Bayes models, statistical inference for large systems, spatial correlation.

Numerical Simulation of Crystallographic Corrosion: Particle Production and Surface Roughness

We use a cellular automaton model to describe corrosion of a metal with crystalline defects. The line defects are distributed over the material mimicking screw or edge dislocations. The line-defect density and the corrosion probabilities of the metal surface site are the model parameters accounting for the crystallographic aspect of corrosion. The corrosion probability is higher for a site located on a line-defect than otherwise. Varying the model parameters, we investigate the roughness of the metal surface considering both its geometrical and chemical aspects. A complicated surface structure with a high geometrical roughness appears if the defect density is not too high. We show a strong correlation between what we call chemical roughness and the properties of the produced particles by the corrosion front. A mean field description is used to analyze the simulation results. For the long time, the simulation results show that the topography of the corrosion front changes from a defect-controlled regime to a situation where the stochastic aspect is the dominant factor.

A comparison of one-stage and two-stage Bayesian processes in engineering decision-making

Engineering decision-making problems often involve conditions that vary spatially either in a continuous way or from element to element. In such cases, the use of two-stage Bayesian models is often advisable in design optimization, maintenance and inspection planning. Two-stage models are based on a ‘state’ or ‘condition’ variable vector that is assumed to be conditionally independent with a pdf given a set of ‘hyper-parameters’. All other process parameters and responses are conditional on this state variable vector. Such models can be applied to a large variety of problems where data from various systems or sources need to be spatially ‘mixed’, such as in deteriorating infrastructure, spatial aspects of corrosion, preference and consequence modeling, and system failure models for large industrial plants. The models are described in detail and an extension is given that allows for the spatial correlation of the individual ‘states’ given the hyper-parameters.

Effects of tungsten on erosion–corrosion behavior of high chromium white cast iron

In this study, effects of tungsten on wear resistance of high chromium white cast iron with and without tungsten in erosion–corrosion condition have been investigated. At the same time, the comparison between wear resistance of this grade of cast iron and low alloy steels with various contents of Cr which are used in industrial condition (in Sarcheshme Company, the greatest copper production company in the Middle East and with more than 4000 years historical cupper production background) was studied, while, copper concentrates have used for erosion particles. Results show that, because of higher hardness of matrix due to the tungsten, the wear resistance of high chromium cast iron increases. In addition to that, combine cutting and deformation wear mechanism and spalling mechanism were attributed in high chromium cast iron and low alloy steels, respectively. Subsequently, pitting mechanism in corrosion aspect was recognized because of inhomogeneity in chemical composition and sulfide inclusions content. Finally, the combine effects of erosion and corrosion (synergetic effect) were recognized in the high chromium white iron in industrial condition for the damaged samples.

Study on strength and corrosion performance for steel embedded in metakaolin blended concrete/mortar

It is an undeniable fact that concrete is the most widely used man-made construction material in the world today, and will remain so for decades to come. The popularity of concrete is largely due to the abundance of raw material, low manufacturing and maintenance cost, excellence in compression, and corrosion aspects, durability to weathering and fire hazards, versatility in forming various shapes and its unlimited structural applications in combination with steel reinforcement. However, the cement industry is also highly energy intensive, and the emission of carbon dioxide during cement manufacturing has created enormous environmental concerns. There has also been an increase in the number of incidents where concrete structures experienced severe deterioration in extreme environments. All these factors have contributed pressures from various quarters to reduce cement consumption, and to intensify research in exploring the possibilities of enhancing strength, durability and corrosion reduction through the use of pozzolans as supplementary cementing materials. The utilization of calcined clay in the form of metakaolin as a pozzolan for concrete has received considerable interest in recent years. The use of metakaolin as a mineral admixture for concrete is a well documented practice. Metakaolin is a quality enhancing pozzolan for concrete. It is manufactured from kaolin which is abundance in India and other parts of the country. In the present investigation mechanical property and corrosion behavior of carbon steel using metakaolin (5–20%) as partial replacement in ordinary Portland cement (OPC). Compressive strength, resistivity, ultra pulse velocity, open circuit potential, studies on water absorption, weight loss were studied. It was found that up to 15% replacement of metakaolin in OPC improves the mechanical properties of concrete. Corrosion of carbon steel improved by the addition of metakaolin up to 15%.

Corrosion and mechanical-microstructural aspects of dissimilar joints of Ti–6Al–4V and Al plates

In this study, Ti–6Al–4V and Al plates were joined by explosive welding at various explosive loads. Tensile-shear, bending, hardness, microstructure and corrosion behaviours of the explosively joined samples were investigated. At the end of the tensile-shear tests carried out according to ASTM D 3165-95 standard, no seperation was observed in the interfaces of the joined samples. The results of the bending tests also showed no sign of any distinctive seperation, crack and tear in the interfaces. The highest hardness values were measured in regions next to interfaces. The optical microscope and SEM examinations revealed that an increment in wavelength and amplitude was observed with increasing explosive load. It is seen from the corrosion test results that materials loss was high at the beginning of the corossion tests but the rate of material loss decreased later on. Furthermore, increasing deformation with increasing explosive load increased the materials loss in corrosion tests.

Studies concerning the durability of concrete vaults for intermediate level radioactive waste disposal: Electrochemical monitoring and corrosion aspects

The Argentine Atomic Energy Commission (CNEA) is responsible of the development of a management nuclear waste disposal programme. This programme contemplates the design and construction of a facility for the final disposal of intermediate-level radioactive waste. The proposed concept is the near-surface monolithic repository similar to those in operation in El Cabril, Spain. The design of this type of repository is based on the use of multiple, independent and redundant barriers. Since the vault and cover are major components of the engineered barriers, the durability of these concrete structures is an important aspect for the facilities integrity. This work presents a laboratory and field investigation performed for the last 6 years on reinforced concrete specimens, in order to predict the service life of the intermediate level radioactive waste disposal vaults from data obtained from electrochemical techniques. On the other hand, the development of sensors that allow on-line measurements of rebar corrosion potential and corrosion current density; incoming oxygen flow that reaches the metal surface; concrete electrical resistivity and chloride concentration is shown. Those sensors, properly embedded in a new full scale vault (nowadays in construction), will allow the monitoring of the corrosion process of the steel rebars embedded in the structure.

Long term corrosion behavior of reinforced concrete structures in chloride environnement

The paper presents different aspects of reinforcement corrosion by analyzing 17 year-old beams kept in a chloride environment under their service load: the corrosion process in relation to cracks, the characterization of initiation and propagation phases and the mechanical behavior in relation to corrosion intensity. The first one concerns the long term behavior of cracked reinforced concrete members exposed in chloride environment. Despite the fact that crack opening is largely superior to the threshold value that affects the ability of chloride ions to diffuse along a crack, results show no correlation with the initial presence of cracks and the intensity of long-term corrosion along the reinforcement. The second one concerns the comparison between the duration of initiation and propagation phase in relation to the covercrete. The third concerns a model of the mechanical behaviour of corroded reinforced concrete members subjected to bending. It is possible to take into account the effect of reinforcement corrosion on the bond between the steel and concrete by increasing the transfer length as a function of the intensity of corrosion. It is possible to forecast a residual mechanical property to help owners to justify that nuclear power plants will kept their serviceability at a given time.

Phosphoric acid anodization of Ti–6Al–4V – Structural and corrosion aspects

Electrodeposited anodic oxide coatings were produced on Ti–6Al–4V from phosphoric acid electrolyte. Different coatings were produced by varying the time periods. Structure of the coatings was analysed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The coatings were exposed to simulated body fluid for a period of 1 month and the weight loss is used to calculate the corrosion rate. Electrochemical polarization and ac impedance studies were performed on the coatings in simulated body fluid and it was found that coatings produced from shorter times showed very good resistance to the attack by this medium.

Corrosion of aluminium and magnesium in BFS composite cements

Legacy radioactive wastes arising from reprocessing of nuclear fuels in the UK are classified as intermediate level waste (ILW), which contain things such as aluminium and magnesium. Blast furnace slag (BFS) composite cements are used to encapsulate ILW. These cements have a high pH which is advantageous to limit the mobility of some of the radioactive species but can cause corrosion of metals. The present paper describes some fundamental aspects of corrosion of aluminium and magnesium in BFS composite cements.The corrosion of aluminium produced an interface between aluminium and cement which was porous with a series of zones containing bayerite (Al(OH)3) and strätlingite (2CaO.Al2O3.SiO2.8H2O). With magnesium, the main corrosion product was found to be brucite (Mg(OH)2) and the porous zone was less pronounced. The hydration of the bulk cement did not appear to be affected by the corrosion of these metals.

Corrosion and Quality

Corrosion is an interaction between a material and its environment that results in deterioration of both. Quality has a wider meaning and designates the suitability of products, management quality and work. Corrosion is a phenomenon, and quality is a philosophical category. The aim of this work is to find common ground between corrosion and quality. We encounter degradation of materials and the environment in everyday life. Corrosion influences the quality of work, products, management, environment and life. The aspects of corrosion correspond to the various meanings of quality. Corrosion costs may be considered as part of the total costs of quality. Corrosion costs are estimated to be as high as 5% of the GNP in various countries.