Erosion-corrosion Process Research Articles

Erosion Corrosion behaviors of Various Metals at different variable

Erosion corrosion process is considered one of the main problems to which too ls, machine parts and equipment are subjected and which operate in fluidized media. Solid particles strike them because of fluid motion at different speeds and varying time periods. Erosion corrosion system was made according to ASTM Specification. Circular test samples were made in diameter 15 mm and length of 50 mm from Al alloy 6061-T6 and Free Cut Brass 360 and polymer. Erosion corrosion test was made using weight loss method in sea water and Tigris river water at 500, 400 and 300 rpm for 1, 2, 3, 4.5.6 hrs. From the results reached, it is found that with increase in time, the erosion corrosion rate increases for both mediums because of the effect of medium components such as chlorine and oxygen for a certain period. When the time period increases, it decreases because the oxygen dissolved in water is used up which is responsible for corrosion. Also a protective is formed from the remnants of corrosion process. Moreover, it is found when speed increases, corrosion rate decreases due to speed prevent ion from summing at electrods.

Visualising the dynamic processes of flow accelerated corrosion and erosion corrosion using an electrochemically integrated electrode array

An electrochemically integrated and individually addressable multi-electrode array has been proposed and demonstrated as a new tool for simulating, visualising and monitoring the dynamic processes of flow accelerated corrosion (FAC) and erosion corrosion under natural corrosion conditions. It has been shown for the first time that FAC and erosion corrosion are able to evolve and propagate freely on the electrode array surface, and that similar corrosion patterns have been observed on the array and coupon surfaces after being exposed to the same flow condition. This method has enabled the visualisation of FAC and erosion corrosion processes with high spatial and temporal resolutions, providing a new means of probing, monitoring and assessing FAC and erosion corrosion and their prevention.

The synergistic effect of cavitation erosion and corrosion of nickel-aluminum copper surface layer on nickel-aluminum bronze alloy

A completely nickel-aluminum-copper (Ni-Al-Cu) layer was obtained through thermal diffusion process on a nickel-aluminum-bronze (NAB) substrate. The cumulative mass loss of the NAB alloy during the cavitation erosion tests was about 6.4 times and 5.5 times as large as that of the Ni-Al-Cu layer in distilled water and 3.5 wt% sodium chloride (NaCl), respectively. Electrochemical measurements under quiescence and cavitation erosion conditions were conducted to investigate the synergistic effects of cavitation erosion and corrosion. The results showed that the synergism had measurable effect on the cavitation erosion-corrosion process for both the NAB alloy and the Ni-Al-Cu layer. The total contribution of the cavitation erosion component including WE and WCIE was more than 80% and WE occupied the largest percentage. Thus, the improved cavitation erosion resistance of the Ni-Al-Cu layer was mainly due to mechanical factors, which implied a homogeneous and refined microstructure and the formation of hardened Ni3Al phase.

Theoretical model and its verification for the effect of sand concentration on the critical flow velocity for erosion–corrosion of 304 stainless steel in 3.5 wt.% NaCl solution

A theoretical model based on fluid dynamics and mechanical analyses was proposed to explain the relationship between the critical flow velocity (CFV) and sand concentration which indicated that the CFV followed a power law of ，i.e. CFV varied with Cm as a power function with exponent of −0.5. Potentiostatic polarisation measurements were performed on 304 stainless steel during the erosion–corrosion process to validate the model. The erosion–corrosion tests were conducted at various flow velocities between 0 and 17 m s−1 and four silica sand concentrations of 2–5 wt.% under the impingement of sand-containing NaCl solution at an impact angle of 90°. It was observed that the anodic current density under a controlled potential increased significantly when the flow velocity was above a critical value. The CFV values of 304 stainless steel under impingement by NaCl solution containing 2–5 wt.% sand are 14, 111, 9 and 8 m s−1, respectively. The experimental results showed that the CFV did follow a power law of sand concentration, while the exponent deviated from the theoretical predicted result. The deviation was attributed to the difference between the actual impact velocity and the inlet flow velocity according to the calculated results by the computational fluid dynamics (CFD) model. And the corrected CFV followed a power law of which was in consistence with the predicted result ().

Erosion-Corrosion Behavior of HVOF WC-Co Coating in Cl− and SO42− Containing Solutions

With the increasingly severe working condition, machine components need to expose to corrosive media including Cl− and SO42− containing environments. In this work, erosion-corrosion properties of HVOF sprayed conventional WC-12Co coating and CeO2 modified WC-12Co coating were tested in 3.5wt.% NaCl solution and 1mol/L H2SO4 solution. Mass loss rate was measured and worn surface were observed to investigate the effects of corrosive media on the erosion-corrosion resistance and mechanism. The results showed that the erosion-corrosion rate was higher at the beginning in 3.5wt.% NaCl solution than that in 1mol/L H2SO4 solution. With a longer time exposure, the absorption and osmosis of SO42− into the microcracks reduced the corrosion resistance and load-supporting capacity of the coatings, resulting in the worse erosion-corrosion resistance than that in NaCl solution. Corrosion-accelerated erosion mechanism dominated the erosion-corrosion process.

Corrosion behavior of Al‐brass alloy during erosion–corrosion process: Effects of jet velocity and sand concentration

Polarization and electrochemical impedance spectrometry measurements were performed on Al‐brass alloy during the erosion–corrosion process. The erosion–corrosion tests were conducted at various SiO2 particle concentrations between 0–90 g/L and three jet velocities of 3, 6, and 9 m/s under an impingement angle of 90°. At a jet velocity of 3 m/s, the results showed a decrease in the corrosion rate at sand concentrations higher than 20 g/L, which was attributed to the particle rebounding effect. At higher jet velocities of 6 and 9 m/s, a continuous increase in the corrosion rate was observed with sand concentration. The results also showed a higher effect of jet velocity on the corrosion rate as compared with the sand concentration. This was related to the increase in the frequency and energy of the impacts by increase in jet velocity, whereas sand concentration could only affect the impact frequency. The role of impact energy on the corrosion rate was determined by calculation of normalized erosion‐enhanced corrosion rate. At high sand concentrations, the normalized erosion‐enhanced corrosion rate of the alloy was a function of second power of jet velocity as was expected by an equation drove from the energy and frequency of impacts.

SCALING DETECTION IN A PIPELINE WITH FLUID UNDER PRESSURE USING NATURAL FREQUENCIES OF FLEXURAL VIBRATIONS

Pipelines can form scale deposits on their walls. Erosion-corrosion processes in pipelines are characterized by the fact that deposition of corrosion products in some of their portions occurs simultaneously with wall thinning in the others. In this paper consideration is given to natural frequencies of flexural vibrations in a pipeline clamped at both ends and subjected to the action of tension force. The pipeline has wall scale deposits and is filled with fluid under pressure. The scale deposits are supposed to be uniformly distributed on the inner surface of the pipeline. Here, the Kirchhoff’s equation for flexural vibrations is applied. The frequency equation has been derived from the equation that dictates the type of flexural vibrations and also the boundary conditions for a pipeline clamped at its ends. Solutions have been found to the primal problem to determine the first and the second natural frequencies of flexural vibrations in the pipeline for the given scale density in the pipeline, axial force, wall thickness, inside pressure of the pipeline and uniform scale thickness on the pipe wall as well as to the inverse problem to determine scale density on the pipe wall and deposition thickness using two natural frequencies of flexural vibrations in the pipeline. It has been found that an increase in the density of scale deposits on the pipe wall results in smaller natural frequencies of pipe flexural vibrations. Besides, the research has shown that a reduction in the pipe inside area or an increase in the scale thickness results in smaller natural frequencies of pipe flexural vibrations. Using two natural frequencies of pipe flexural vibrations we can determine the density of scale deposits on the pipe wall and pipe inside area or scale thickness. The investigation outcomes can be applied to assess axial loading and pipe wall thickness using two natural frequencies of flexural vibrations.

Evaluation of Cavitation Erosion-Corrosion Process of Q235 and ZG06Cr13Ni4Mo With Various Applied Potentials

Evaluation of Cavitation Erosion-Corrosion Process of Q235 and ZG06Cr13Ni4Mo With Various Applied Potentials

Effect of erosion speed on the interaction between erosion and corrosion of the Fe–3.5 wt% B alloy in a flowing zinc bath

Abstract

Corrosion behavior of ZHMn55-3-1 copper alloy in stagnant and flowing seawater with entrained sediment

Purpose – The purpose of this investigation was to study the erosion-corrosion behavior of ZHMn55-3-1 copper alloy in seawater (flow velocity from 0 to 0.8 m/s, sediment content from 0 to 0.15 percent), to analyze the effects of the flow velocity and sediment content on the erosion-corrosion process. Design/methodology/approach – A simulated erosion-corrosion test system was set up. Weight loss determinations and electrochemical measurements (such as potentiostat square wave (PSW), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests) were used to study the erosion-corrosion behavior of ZHMn55-3-1 copper alloy in stagnant and flowing seawater with different sediment contents. Findings – Under the test conditions, ZHMn55-3-1 copper alloys had good corrosion resistance to stagnant clear seawater, while increasing the flow velocity and sediment content reduced the corrosion resistance of the material. The difference in the erosion-corrosion mechanism between flow velocity and sediment content was that the former affected both the cathode process and the anode process of electrochemical corrosion, while the latter essentially affected only the anode process. Originality/value – This paper explains the effects of flow velocity and sediment content on the erosion-corrosion behavior of ZHMn55-3-1 copper alloy in flowing seawater.

Surface Characterization and Erosion–Corrosion Behavior of Q235 Steel in Dynamic Flow

The study aims at investigating the surface evolution and erosion–corrosion behavior of Q235 steel during erosion–corrosion process in various dynamic flows. For the purpose, true flow fields with the average flow velocities of 0.4 and 0.8 m/s and impact angles of 0°, 30° and 90° to the sample surface were successfully measured by particle image velocimetry. The topography of erosion–corrosion surface was observed by laser scanning confocal microscopy. The evolution of localized corrosion pattern is found to be determined by impact angle, i.e., round or elliptical corrosion pit corresponds to impact angle of 90° and ribbon-like corrosion pit corresponds to 0°. The deeper corrosion pits were observed at impact angle of 30° than those at the other two impact angles owing to combined effects of shear and normal stresses. Electrochemical impedance spectroscopy of samples shows smaller radiuses of capacitive loops at velocity of 0.8 m/s than those at 0.4 m/s. Equivalent circuit analysis implies unstable surface state of sample in dynamic flow. Above results indicate that the flow velocity and impact angle play the key role in the erosion–corrosion behavior of Q235 steel.

Problems relating to operation of geothermal power stations stemming from the presence of admixtures in the geothermal heat carrier

The effects the specific features of chemical composition and the thermophysical properties of geothermal heat carrier have on the metal erosion-corrosion processes and on the formation of deposits during operation of a geothermal power station are analyzed. Methods for preventing the formation of deposits and making the geothermal power station equipment more resistant to erosion and corrosion are considered. Results from calculation and experimental investigations aimed at studying how the concentration of silicic acid and other admixtures vary in the working loop and turbine flow path at the Verkhne-Mutnovsk geothermal power station are presented. The possibility of using surface-active inhibitors to prevent the formation of deposits and erosion-corrosion processes in the geothermal power station equipment is demonstrated.

Selective Removal of Cs+, Sr2+, and Ni2+ by K2xMgxSn3–xS6 (x = 0.5–1) (KMS-2) Relevant to Nuclear Waste Remediation

137Cs and 90Sr, both byproducts of the uranium and plutonium fission processes, make up the majority of high-level waste from nuclear power plants. 63Ni is a byproduct of the erosion-corrosion process of the reactor components in nuclear energy plants. The concentrations of these ions in solution determine the Waste Class (A, B, or C); thus, their selective removal in the presence of large excesses of nonradioactive ions is necessary to reduce waste volume and cut disposal costs. We report the new material K2xMgxSn3–xS6 (x = 0.5–1, KMS-2) and its application for the ion exchange of Cs+, Sr2+, and Ni2+ in varying conditions. This compound crystallizes in the hexagonal space group P63/mmc with cell parameters a = b = 3.6749(8) A and c = 16.827(4) A. The difference in crystal structure between KMS-2, the previously reported Mn analog K2xMnxSn3–xS6 (KMS-1), and their parent SnS2 is also described. Distribution coefficients for KMS-2 are high for Cs+ (7.1 × 103 mL/g) and Sr2+ (2.1 × 104 mL/g) at neutral pH (∼ ...

Preventing inadmissible erosion-corrosion thinning from occurring in the diffuser segments of feedwater supply control systems of power units at nuclear power stations equipped with RBMK-1000 reactors

Results obtained from investigations of erosion-corrosion processes that occur during operation of the feedwater supply control systems used in power units of nuclear power stations equipped with RBMK-1000 reactors and the sensitivity of these processes to variations in the chemical composition of metal and in the flow path geometry are presented. It is found that local erosion-corrosion thinning of the walls in the diffuser segments of feedwater supply control systems occur mainly due to intense mass transfer in the near-wall region taken in combination with a low content of chromium. Hydrodynamic simulation was carried out, and it was shown based on its results that local erosion-corrosion thinning of the walls of pipeline segments downstream of the valves controlling the supply of feedwater to power units of nuclear power stations equipped with RBMK-1000 reactors can be prevented by subjecting them to appropriate modernization. It is found that the above mentioned diffuser parts can be made more resistant to erosion-corrosion wear by keeping the content of chromium in the main metal and weld joints at a level of no less than 0.25% and concurrently reducing the hydrodynamic effect in the zones of weld connections.

The synergistic effect between erosion and corrosion of API pipeline in CO2 and saline medium

Erosion–corrosion is common in oil and gas processing plants and pipelines where there is interaction between solid particles, corrosive fluid and target material. The objective of the present work is to assess the synergism between erosion and corrosion of API X-70 pipeline steel under liquid–solid impingement conditions in 2g/l NaCl solution purged with CO2 as the corrosive (acidic) media and aluminum oxide as the erodent. The total material loss rate, the components of erosion, corrosion and their synergistic interactions have been determined. The experimental results show that there is an immense correlation exists between erosion and corrosion. During erosion–corrosion, erosion enhances corrosion and corrosion enhances erosion resulting in higher material loss. Scanning electron microscopy analysis of the worn specimen reveals that plastic deformation and fracture are the dominant mechanisms during the erosion–corrosion process. Furthermore, corrosion removes the work hardened layer and exposes a stress free surface for erosion while erosion removes the passive film from the surface and creates a work hardened layer which is highly susceptible to corrosion.

Determination of the best behavior among AISI D3 steel, 304 stainless steel and CrN/AlN coatings under erosive-corrosive effect

The erosive-corrosive effect of aqueous NaCl slurries on metals and metals coated with a multilayer system was analyzed. The erosion-corrosion experiments were performed in a test machine in which the impingement velocity, impact angle, concentration of solids and pH of the solution were controlled. Polarization curves were simultaneously obtained to correlate the electrochemical effects to the erosive wear mechanisms. The slurry used consists of silica particles suspended in a mixture of acid solution and 3.5% NaCl, with a pH value of 5.6. Electrochemical results showed the best corrosion resistance for steel coated with CrN/AlN system deposited with 50 bilayer. Additionally, the surface analysis by SEM micrograph revealed formation of cracks in CrN/AlN multilayers coating and plastic deformation in both steel substrates (AISI D3 steel and 304 stainless steel), especially when the mean impact angle is a critical value of 90°. Measurements of critical and passive current densities showed that the behavior of coated materials differed depending on the substrate that is used. Nonetheless, in a general way, by increasing the impact angle and by changing its incidence from normal to grazing, it led to an improved resistance to erosion-corrosion processes.

Mapping erosion–corrosion of carbon steel in oil–water solutions: Effects of velocity and applied potential

In this study, the erosion–corrosion performance of carbon steel was investigated in crude oil, reservoir water, and a mixture of both solutions at a range of applied potentials, velocities and impact angle. The application of such work is to upstream and downstream oilfield conditions, where the proportions of hydrocarbon and water may vary during the extraction process over time. Following exposure of the carbon steel in the crude oil, the extent of erosion was greater than that of corrosion, whilst in the reservoir water, the erosion and corrosion contributions were similar. Regimes of erosion–corrosion were proposed based on the variation in erosion behaviour at various impact angles and applied potentials in the environments studied. Mechanistic changes were identified on erosion–corrosion maps as a function of velocity and applied potential at various impact angles, indicating important transitions in erosion–corrosion processes in the oil/water environments.

Simulation of corrosion-erosion of passive metals using a micro-scale dynamical model

This article reports our recent efforts in extending a micro-scale dynamical model (MSDM), which was originally developed to model mechanical wear, to simulation of erosion-corrosion or corrosive wear of passive metallic by taking into account of chemical and mechanical properties of passive films as well as the competition between passivation and failure of passive films during corrosive wear processes. In this model, the target material is discretized and mapped onto to a discrete lattice. Each lattice represents a small volume of the material. The site-site interaction is dependent on mechanical properties of the material. For erosion-corrosion involving solid particle impingement in corrosive slurry, each ejected solid particle is also discretized and treated in a similar way. Determined by the activity of the target metal, the lattice sites are classified into two groups: active and passive sites. During an erosion-corrosion process, passive lattice sites on surface, which protect the inner active lattice sites from being corroded, could be damaged or worn away by the impingement of ejected particles. When the passive sites on surface are removed and active lattice sites underneath are exposed to the corrosive solution, they begin to transform from an active state to a passive state, corresponding to the development of passive film. The active lattice sites continuously degrade until a complete passive film forms. The dissolution rate of the target metal is influenced by the passivation state and the deformation of the adjacent lattice regions. In order to evaluate the effectiveness of this model in simulating corrosive wear, erosion-corrosion of 304 stainless steel is simulated and preliminary comparison between modeling and experiments is made.

Assessing the resistance of metal matrix composites and their microstructural integrity under erosion–corrosion

Abstract Materials and machinery components handling corrosive slurries are exposed to erosion–corrosion (EC) processes that significantly reduce their service lifetime. Difficulties predicting material loss in industrial machinery, financial and security impacts due to early failure of worn components and the necessity of managing highly aggressive slurries (e.g. oilsands), have motivated the application of surface engineering solutions to reduce the negative effects of erosion–corrosion processes. The erosion–corrosion resistance of nickel base and iron base metal matrix composites (C Ni and C Fe MMCs, respectively) coatings was studied in this paper. The behavior of the MMCs compared with their non-reinforced matrices (NRMs); tungsten carbides (WC) particles were used to reinforce the NRMs. The microstructures of the NRMs and MMCs were analyzed by microscopy techniques and the effects of adding a reinforcing phase to the matrices are reported and linked to their EC resistance. The EC resistance was assessed at different sand contents (10 and 50 g/l) and temperatures (20 and 65 °C) using a submerged impinging jet (SIJ) apparatus; the MMCs were also studied under EC at 5, 10 and 14 m/s to analyze the structural integrity of the reinforcing phase. The results shown that, the C Ni was the more EC resistant coating under most of the experimental conditions, at 5 m/s the EC degradation mechanism was dominated by matrix degradation with the WC showing little damage and the C Fe was negatively affected by corrosion, especially at 65 °C. Interestingly, the MMCs were more susceptible to changes in temperature whereas, for the NRMs EC resistance was more affected by the sand content of the slurry.

Corrosion and Erosion-Corrosion Processes of Metal-Matrix Composites in Slurry Conditions

The corrosion and erosion-corrosion (EC) processes of four metal-matrix composites (MMCs) in a simulated cooling water environment have been assessed in this article. The MMCs consisted of two Ni-base and two Fe-base matrices alloyed with different concentrations of chromium, molybdenum, boron, silicon, and carbon; the matrices were reinforced with tungsten carbide (WC) particles. The corrosion behavior has been investigated using a combination of potentiostatic polarization and post-tests surface analysis. The EC processes were studied by in situ electrochemical techniques measuring the current density and corrosion potential response at different slurry temperatures and sand content. At static conditions it was found that as the temperature increased, there was a transition from a homogeneous corrosion of the matrix to an interfacial corrosion mechanism. The Ni-base MMCs showed a better corrosion resistance and interestingly a highly alloyed matrix did not significantly improved MMC’s corrosion resistance. In the in situ EC tests, the Fe-base MMCs showed a constant increase in the current density at all sand contents. Whereas, significant changes were not observed in the Ni-base MMCs below 0.5 g/L. Although sand content had an effect on the monitored current density (the current increased as the sand content increased) this effect was less pronounced above 3 g/L.