Erosion-corrosion Regimes Research Articles

On the Interaction Between Erosion and Corrosion in Chromium Carbide Coating

In this paper, the effects of slurry flow velocity and impact angle on erosion–corrosion (E–C) behavior of the chromium carbide coating in NaCl solution containing SiO2 particle were investigated. A jet impingement system was used. The mass loss test, polarization curve and surface characterization were employed to examine the coating performance. The erosion–corrosion regime of the Cr7C3-coated and uncoated specimens was determined. Results showed that pure erosion and corrosion-enhanced erosion were the dominant regime for the uncoated samples. However, both the erosion and corrosion contributed to the coating damage. Mass loss values of the coated and uncoated samples increase with flow velocity. In addition, coated and uncoated samples experience maximum mass loss at 45° and 90°, respectively. Finally, E–C degradation mechanisms were evaluated using scanning electron microscopy. The images indicate the abrasive wear mechanism and lips removal as well as plastic deformation for the uncoated sample. Also, brittle fracture, cracking and flake fragmentation were recommended as the main fracture mechanism for the chromium carbide coating.

Influence of intermittent flow sub-patterns on erosion-corrosion in horizontal pipe

Thinning of pipe wall due to erosion and corrosion has resulted in many catastrophic failures and huge economic losses in petroleum refineries (Wood et al., 2013) and nuclear power stations (Ahmed, 2012). The intermittent structure of two-phase flow through pipe (intermittent flow regime) is an important factor responsible for such erosion and corrosion. The present research is an effort to develop a regime map showing possible erosion and corrosion phenomena due to intermittent flows in pipe. In this direction, flow visualization experiments are carried out for three distinct sub-regimes of intermittent flow namely, plug flow with or without bubble rim, less aerated slug flow and highly aerated slug flow. Images captured at a rate of 1600 frames per second at 288 diameter downstream of inlet are utilised for analysing the dynamics of intermittent flow structure in terms of expansion, contraction, breaking, coalescence, collapse, and collision of bubbles. Quantitative measurements of intermittent flow characteristics (including plug/slug frequency, plug/slug velocity and length of liquid plug/slug) and their influence on erosion-corrosion phenomena in the pipe are reported in detail. Based on these qualitative and quantitative analysis, a regime map for prediction of erosion-corrosion phenomena in pipes is established as a function of inlet flow conditions for both the phases. Transition boundaries for four distinct erosion-corrosion phenomena: shear stress induced erosion, cavitation erosion, liquid impact induced erosion and flow accelerated corrosion are represented in the map and eight distinct regimes of erosion-corrosion are illustrated. The regime map is represented in terms of non-dimensional superficial Reynolds numbers of both the phases to account for pipe diameter, flow rate and fluid viscosity. This erosion-corrosion regime map developed in this research will immensely aid to the effective design of piping systems and optimization of operating conditions for safer operation of petroleum refineries and nuclear power stations.

Effects of Cr3C2 addition on the erosion–corrosion resistance of Ti(C,N)-based cermets in alkaline conditions

Effects of Cr3C2 on the erosion–corrosion behavior of Ti(C,N)-based cermets are studied in alkaline conditions. The results indicate that the erosion–corrosion resistance of cermets is improved with proper Cr3C2 content. Corrosion performance of cermets is deteriorated by Cr3C2 addition in NaOH solution. With the increase of Cr3C2, the erosion–corrosion behavior of Ti(C,N)-based cermets is classified to be erosion regime, erosion–corrosion regime, corrosion–erosion regime and corrosion regime. Materials degradation is determined by particles erosion for cermets with low Cr3C2 content, while for materials containing more Cr3C2 addition, binder corrosion and subsequent erosion are responsible for materials deterioration.

A CFD model of particle concentration effects on erosion–corrosion of Fe in aqueous conditions

A CFD (computational fluid dynamics) model has been developed to evaluate the effects of particle concentration on the erosion–corrosion of the inner surfaces of a circular pipe of 90° bend at room temperatures. The relative intensity of erosion and corrosion around the pipe geometry results in transitions between various erosion–corrosion regimes, for a given inlet particle concentration. The results indicate that the corrosion-dominated regime at the pipe bend is reduced with an increase in particle concentration. Typical results from the model are shown illustrating how this 3D mapping method can be used to model parameters such as particle concentration on the erosion–corrosion regimes over the surface.

Some perspectives on modelling the effect of temperature on the erosion–corrosion of Fe in aqueous conditions

In this paper, a model is generated of the effect of temperature on the erosion–corrosion of Fe in aqueous conditions, for room temperature to 373 K. The results indicate how the transition from active to passivation dominated regimes for Fe is favoured as the temperature is increased. 2D and 3D maps are constructed showing the transitions between erosion–corrosion regimes.

Mapping erosion-corrosion of carbon steel in oil exploration conditions: Some new approaches to characterizing mechanisms and synergies

Erosion by solid particles in oil/water slurries is a technologically important area. In such conditions, it is necessary to distinguish between the effects of the sand, aqueous environment, and the oil. Erosion–corrosion maps provide a means of identification between erosion–corrosion regimes as a function of erosion and corrosion parameters. However, there has been no work carried out to map the effects of parameters in oil/water slurries. This paper investigates the effect of erosion–corrosion on carbon steel in oil field production and maps the results. Distinctions between “synergistic” and “additive” erosion–corrosion behaviour are superimposed on the maps in the various environments.

A new methodology for modelling erosion–corrosion regimes on real surfaces: Gliding down the galvanic series for a range of metal-corrosion systems

Erosion–corrosion of materials in aqueous environments is a complex phenomenon involving a very large number of variables. In such cases, characteristics of the target, particle and the environment affect the degradation mechanism. Predicting material behaviour may sometimes be a “black art” due to the parameter size which is involved in such processes.In studies of erosion–corrosion, there have been significant advances in the modelling of such processes in recent years. Various methodologies employed include quasi-static modelling, using CFD modelling and erosion–corrosion mapping. In such cases, the output of the various models can differ significantly.In this work, a methodology combining CFD modelling and erosion–corrosion mapping has been developed to model the erosion–corrosion behaviour of pure metals, which variously passivate and dissolve under a range of simulated conditions. This provides a means of mapping the component undergoing erosion–corrosion and thus is a step change on previous modelling work in this area as it enables superimposition of the erosion–corrosion map on real surfaces. The relative advantages and limitations of this approach are discussed in this paper.

CO 2 erosion–corrosion of pipeline steel (API X65) in oil and gas conditions—A systematic approach

A systematic study of pipeline steel (API X65) degradation due to erosion–corrosion containing sand in a CO 2 saturated environment has been carried out. This work focuses on the total material loss, corrosion, erosion and their interactions (synergy) as a function of environmental parameters (temperature, flow velocity and sand content) to enable the critical conditions, which move the damage mechanism from a flow-induced corrosion regime to erosion–corrosion regime, to be determined. The experimental results show that the effect of corrosion in enhancing erosion, often referred to as the synergy, is significant and accounts for a high proportion of the deviation of measured material loss from the prediction derived from established CO 2 corrosion models. Ways forward to improve erosion–corrosion prediction are discussed.

Mapping erosion–corrosion of WC/Co–Cr based composite coatings: Particle velocity and applied potential effects

In studies of erosion–corrosion of composite based coatings, there have been few attempts to map the mechanisms of the erosion–corrosion process. This is despite the fact cermet-based coatings are being increasingly used to combat erosion on pipelines and pumps where the degradation is caused by a combination of sand particles and seawater. In addition, the interactions between the processes of erosion and corrosion have only been evaluated for a limited range of conditions, despite the fact that erosion–corrosion occurs over a wide range of variables in practice. In this study, the effects of velocity, particle concentration and potential were evaluated for a WC/Co–Cr based coating. The extent of wastage was assessed using scanning electron microscopy and weight loss techniques. Mechanisms of erosion–corrosion were identified from the results. The results were used to generate erosion–corrosion mechanism maps for the coated and uncoated specimens. Velocity/potential maps were constructed showing the transitions between the erosion–corrosion regimes as a function of these parameters. The extent of synergy was also superimposed on such maps, showing the conditions where synergistic effects were likely to be at a minimum for the main process parameters.

Modelling particulate erosion–corrosion regime transitions for Al/Al 2O 3 and Cu/Al 2O 3 MMCs in aqueous conditions

Very little research effort has been directed at development of models of erosion–corrosion of composite materials. This is because, in part, the understanding of the erosion–corrosion mechanisms of such materials is poor. In addition, although there has been a significant degree of effort in the development of models for erosion of MMCs, there are still difficulties in applying such models to the laboratory trends on erosion rate. In this paper, the methodology for mapping erosion–corrosion processes in aqueous slurries was extended to particulate composites. An inverse rule of mixtures was used for the construction of the erosion model for the particulate MMCs. The corrosion rate calculation was evaluated with reference to the matrix material. The erosion–corrosion maps for composites showed significant dependency on pH and applied potential. In addition, the corrosion resistance of the matrix material was observed to affect the regime boundaries. Materials maps were generated based on the results to show the optimum composite composition for exposure to the environment.

Erosion-Corrosion of Stainless Steels in Aqueous Slurries—A Quantitative Estimation of Synergistic Effects

Abstract The synergism between erosion and corrosion of stainless steels (SS) in 3.5 wt% sodium chloride (NaCl) + 0.5 N sulfuric acid (H2SO4) + 30 wt% aluminum oxide (Al2O3) dual-phase fluid has been studied by means of a rotating cylinder electrode apparatus. The erosion/erosion-corrosion behavior of several SS, 1Cr13 (ferritic), Type 316L (austenitic [UNS S31603]), 0Cr14Ni5Mo (martensitic), and CD-4MCu (α+γ duplex), were investigated further to illustrate the synergistic mechanism. The experimental results showed that CD-4MCu had a higher erosion-corrosion resistance because of its excellent deformation strengthening capability. By measuring and calculating each component of the synergistic interaction, it could be concluded that the removal of material mainly came from the mechanical damage in the condition of this study. Based on the classification of erosion-corrosion regimes with respect to the ratio of erosion to corrosion rate, the synergistic mechanism of erosion-corrosion of SS in the condition ...

Impact angle effects on the erosion–corrosion of superlattice CrN/NbN PVD coatings

Wastage due to the combined effects of erosion and corrosion is a serious issue in a wide range of industrial environments. The extent of wastage is dependent on a range of parameters relating to properties of the particle, target and the environment. In such cases, surface engineering (through providing a protective coating) may be used to avoid the deleterious effects of both processes. In recent years, there has been an increasing interest in the potential of CrN/NbN superlattice PVD coatings to provide resistance to erosion–corrosion in such conditions. Initial studies on the effects of velocity have shown that they significantly outperform conventional coatings, although the behaviour depends on the conditions. There is however, poor understanding on the effects of many important tribological variables, such as particle size and impact angle, on the performance of such coatings. In this work, the effect of impact angle on the erosion–corrosion of a range of CrN/NbN superlattice coatings was assessed at a range of applied potentials in a carbonate/bicarbonate solution. The mechanisms of erosion–corrosion of the coatings, as a function of impact angle and applied potential, showed significant differences when these parameters were varied. Erosion–corrosion maps were constructed based on these results showing the change in mechanisms and wastage rates as a function of impact angle and applied potential. Possible reasons for the differences in erosion–corrosion regimes for coated and uncoated specimens are described in this paper.

Modelling particulate erosion–corrosion in aqueous slurries: some views on the construction of erosion–corrosion maps for a range of pure metals

In studies of erosion–corrosion by solid particles in aqueous conditions, there have been various attempts in recent years to model the process. In particular, predictive models have been developed for steels to chart transitions between erosion–corrosion regimes. Such regimes identify whether the erosion–corrosion process is affected by active dissolution or passivation processes in the aqueous environment. A very important development in the study of aqueous corrosion of pure metals has been the concept of the corrosion map, developed by Pourbaix in the last century. Such maps identify regimes of corrosion, ranging from immunity to active dissolution and to passivation, as a function of pH and electrochemical potential. The position of the boundaries, as a function of the latter variables, may differ significantly for various pure metals. This paper models the erosion–corrosion behaviour for a range of pure metals, i.e. Ni, Al, and Cu (metals which have not been addressed to date using such an approach) and compares the results with a reference metal, Fe. Erosion–corrosion mechanism and wastage maps are constructed based on the results. In addition, materials selection maps are developed based on the results, showing how erosion–corrosion resistance for the materials may be optimised in such conditions.

Erosion–corrosion of chromium steel in a rotating cylinder electrode system: some comments on particle size effects

The effect of particle size on the erosion–corrosion response of a Cr containing steel in NaOH was studied in a rotating cylinder electrode system. The results showed that for the same addition of particles by weight, the corrosion rate in the presence of erosion was independent of particle size. However, the erosion–corrosion rate appeared to be dependent on particle sizes for size ranges from 50 to 100 μm but above this value, this dependence was reduced. Erosion–corrosion mechanism and wastage maps were constructed based on the results showing the variation in erosion–corrosion regimes, as a function of particle size and electrochemical potential.

Erosion–corrosion mapping of Fe in aqueous slurries: some views on a new rationale for defining the erosion–corrosion interaction

In studies of erosion–corrosion of materials in aqueous conditions, there have been various attempts to define regimes of interaction. Such regimes indicate whether erosion or corrosion may dominate the wastage mechanism. However, intermediate regimes in which corrosion and erosion interact with each other may lead to situations where the wastage is far greater than the sum of the processes acting separately. A common method of defining erosion–corrosion interactions has been to distinguish between the regime in which erosion enhances the corrosion rate (the so called “additive effect” because the corrosion contribution can be measured electrochemically and thus added to the erosion contribution to assess the overall wastage rate) and the regime where corrosion enhances erosion (the so-called “synergistic” effect). However, regimes of erosion–corrosion, where corrosion impedes the erosion are also of great importance mechanistically, and usually these are termed as exhibiting “negative synergism”. Defining the conditions in which a transition from “positive” to “negative synergism” occurs, is useful in order to optimize the parameters to minimize the wastage rate. This paper reviews the rationale that has been used to define erosion–corrosion regimes in aqueous conditions as part of a study of the erosion–corrosion of Fe at various pHs. The mathematical definitions are discussed in relation to practical erosion–corrosion problems. In addition, a new “antagonistic” erosion–corrosion regime is proposed to properly define the concept of “negative synergism”.

Erosion of construction materials in a reverse osmosis plant utilizing seawater in Kuwait

The development and production of fresh potable water by reverse osmosis (RO) from the high saline Arabian Gulf sea requires several considerations. Among the number of considerations are minimized energy consumption, improved membrane performance, increased recovery and salt rejection, and improved materials of construction. The state-of-the-art for selection of appropriate corrosion-resistant alloys for a specific environment is not sufficiently advanced to make the obvious choices for a specific environment. Many metallic components in RO units still exhibit corrosion attacks in different forms. Localized corrosion in the form of pitting and crevice and mechanically induced erosion-corrosion are some of the problems behind many of the failures in RO equipment. It still remains necessary to conduct laboratory and plant testing of candidate alloys to establish those alloys that may be suitable for use. Results of laboratory tests conducted on a number of candidate construction materials for the various components and piping systems are described. The materials were exposed to an erosion-corrosion regime.

Simplifying the erosion–corrosion mechanism map for erosion of thin coatings in aqueous slurries

A significant advance in the study of erosive wear in recent years has been the construction of erosion mechanism maps showing the transitions between the erosion–corrosion regimes as a function of the main process parameters. The various corrosion regimes, ranging from active to passive conditions, have been incorporated on the map. Hence, the map is more complex than that in dry oxidizing conditions where the predominant corrosion process is film growth. The object of this work has been to study the combined effects of increasing erodent velocity and applied potential on the erosion of PVD coatings, i.e., Ti 2N and CrN in aqueous conditions. The substrate was mild steel, the particles alumina and the solution, a carbonate–bicarbonate buffer. Mechanisms of erosion–corrosion were identified on the basis of the results. The erosion mechanism maps generated from the results provided a means of differentiating between erosion–corrosion behaviour of the coating and the substrate. Significant shifts in the boundaries were identified for different coatings. The stages in the construction of such maps, in addition to the various approaches towards simplifying the nomenclature and the format, are described in this paper.

Some thoughts on the construction of erosion–corrosion maps for PVD coated steels in aqueous environments

In studies of erosion-corrosion of materials in aqueous conditions, there have been a few attempts to evaluate the performance of coatings. This is despite the fact that the use of coatings provides a relatively economic method of reducing erosion-corrosion damage in such environments. There has also, as a consequence, been no attempt to define a rationale for coating selection for exposure to various erosion-corrosion environments. The object of this work has been to address the above issues by investigating the effect of increasing velocity on a range of physical vapour deposition (PVD) coated and uncoated steels, at various applied potentials, in a carbonate/bicarbonate slurry solution containing alumina particles. The performance of two coatings, Ti2N and CrN was evaluated. The results were compared to those for the uncoated steel (mild steel) and 304 stainless steel, The results showed that the both the corrosion and passivation potentials for the coatings occurred at different values for the individual coatings. Hence, the erosion-corrosion regime maps differed for the different coating systems. Materials performance maps were constructed from the results, providing a basis by which the use of such coatings may be optimized for exposure to aqueous erosion-corrosion conditions. (C) 1999 Elsevier Science S.A. All rights reserved.

A methodology for the construction of the erosion-corrosion map in aqueous environments

For the erosion of alloys under aqueous conditions, there have been some recent attempts to identify the transitions between the erosion-corrosion regimes using laboratory results. Such transitions can be superimposed on an erosion-corrosion map as a function of the main corrosion and erosion variables. Defining the magnitude of the wastage rate on such maps enables the relevant process parameters involved in the damage process to be optimized. The object of this work was to model the erosion-corrosion behaviour of mild steel exposed to an aqueous solution containing alumina particles. The results were used to identify the transitions between the erosion-corrosion regimes on erosion-corrosion mechanism maps. Process control maps, which show the magnitude of the wastage rate, were also constructed using such an approach. This paper describes the basis of the mathematical models used to construct the boundaries on the maps. The effects of particle size, flux, and solution pH on such boundaries are demonstrated. In addition, a qualitative comparison is made between the results of the model, and a series of slurry erosion-corrosion tests of mild steel in aqueous media.

Effects of particle velocity and applied potential on erosion of mild steel in carbonate/bicarbonate slurry

The present paper describes a study of the combined effects of velocity and applied electrochemical potential on the erosion of mild steel in an aqueous carbonate/bicarbonate slurry. The erodent used was alumina; the velocity was varied between 2 and 10m s−1 and the potential between −1·0 and 0·2 V (saturated calomel electrode). Measurements were made of the erosion rate in the absence of corrosion (when the surfaces were cathodically protected), the instantaneous corrosion rate, and the overall erosion–corrosion rate. The results showed that the effect of velocity varied as a function of the applied potential. Velocity exponents were evaluated for the various erosion–corrosion conditions, and the trends in the variation of the exponents were discussed for each of the applied potentials. Criteria for the existence of erosion–corrosion regimes in aqueous environments were suggested, and were used to generate an erosion–corrosion map based on the experimental data.MST/3364