Erosion-corrosion Interactions Research Articles

Laser-based fabrication of superwetting titanium alloy with enhanced corrosion and erosion-corrosion resistance

Titanium (Ti) alloy is vulnerable to erosion and corrosion effect of sea water in the application of marine equipment and prone to degradation and failure. In order to further enhance the erosion-corrosion resistance of Ti alloy, a laser-heat hybrid treatment is applied to fabricate superwetting Ti alloy surface. The surface morphology, chemical composition and surface wettability of Ti alloy before and after laser processing are characterized. The surface behaviors of the superwetting Ti alloy surface during corrosion and erosion-corrosion interaction are evaluated by electrochemical station and two-phase flow erosion equipment. The experimental results indicate that the periodic micro-bump structure induced by laser texturing and the low surface energy after heat treatment contribute to the surface wettability transformation into superhydrophobicity with the contact angle of 156.2°. Compared with the untreated Ti alloy surface, the laser-heat-treated superhydrophobic surface exhibits a smaller corrosion current density and a larger potential in NaCl solution, showing better corrosion resistance. The surface erosion-corrosion resistance has also been increased by 18% due to the decrease of solid-liquid contact area caused by air cavity of superhydrophobic surface. This can provide a solid laser-based fabrication method of Ti alloy for long-term and stable application in marine environment.

Flow Velocity and Sand Loading Effect on Erosion–Corrosion during Liquid-Solid Impingement on Mild Steel

The presence of CO2, sand, and water in oil and gas reservoirs causes erosion–corrosion leading to material degradation in pipelines and fluid handling equipment that results in increasing maintenance and repair costs and a decrease in production. While the weight loss caused by erosion–corrosion is known to depend on flow velocity, angle of impact, sand loading and size and target material properties, field operators often limit the flow rate based on a critical corrosion velocity to protect the equipment. This study investigates the effects of sand loading and flow velocity on weight loss associated with erosion–corrosion in a mild steel sample using a submerged impingement jet. The weight loss by erosion, corrosion and their interaction for a flow velocity range of 10 m/s to 20 m/s and sand loading range of 300 mg/L to 600 mg/L, in a seawater environment, are presented. The results showed that the weight loss by pure erosion and erosion–corrosion interaction increases linearly with jet velocity and sand loading, and that erosion is dominant in all cases except at low velocity and sand loading. The scanning electron microscope (SEM) images after impingement tests were analyzed. In addition, correlations for the velocity and sand loading were derived using the design of experiment method (DOE).

On a multiphysics approach to modelling the erosion–enhanced corrosion of low–alloy carbon steel in chloride containing environments

The effect of chloride on erosion-enhanced corrosion was studied experimentally and by a multiphysics algorithm developed to describe the erosion-corrosion interactions. API 5 L X65 steel was exposed to a slurry jet of different chloride content (0.005, 0.05 or 0.5 M) containing silica particles (250–350 μm). An electrochemical-transport-reaction model was used for numerical simulation of polarization curves. Visualization of the flow conditions was also carried out in this work. The effect of erosion on corrosion was found to be well described as a proportionality factor between the kinetics constants of the electrochemical reactions with and without the erodent. The presence of chloride was found to affect the system mainly through increased conductivity of the electrolyte.

Design of an elbow for integrated gravimetric, electrochemical and acoustic emission measurements in erosion-corrosion pipe flow environments

Erosion-corrosion degradation in oil and gas pipelines is a significant problem, and a change in flow geometry can significantly enhance rates of degradation. In this study, a 3D printed 90° elbow, integrated into a flow loop, was developed to evaluate erosion-corrosion of X65 carbon steel along both the inner and outer internal portions of the bend in an aqueous carbon dioxide (CO2)-saturated environment containing sand particles. Designing representative geometries capable of measuring rates of corrosion, erosion and their synergistic interactions, can be challenging and currently no designs have been reported in literature that effectively integrate the required measuring techniques to determine local degradation rates throughout the component. To elucidate the individual contributions to overall erosion-corrosion degradation rates, gravimetric and electrochemical measurement techniques were used to quantify degradation rates at multiple locations in the flow geometry, with the specimen design also enabling the possibility of completing acoustic emission measurements to detect particle impacts. The design of the elbow is presented and erosion-corrosion tests were conducted to determine the magnitude and individual contributions of erosion, corrosion and erosion-corrosion interactions at a flow velocity of 6 m/s in a CO2-saturated, pH 4, 60 °C, 2 wt% NaCl solution containing 1000 mg/L of sand particles.

Erosion-corrosion interactions of X65 carbon steel in aqueous CO2 environments

When sand is present in carbon dioxide (CO2) corrosion environments in carbon steel oil and gas pipelines, wear rates can be particularly severe. The wear mechanism when surfaces are exposed to impact by a solid-laden corrosive fluid is known as erosion-corrosion and consists of erosion and corrosion components with total erosion-corrosion degradation enhanced by interactions between erosion and corrosion. The causes of corrosion-enhanced erosion and erosion-enhanced corrosion of carbon steel, in this regime, are not fully understood and are the subject of study in this work in a 60 °C, pH 4.7, 2% NaCl solution, containing 1000 mg/L of sand particles with an average diameter of 250 µm, flowing through a submerged impinging jet (SIJ) nozzle at 20 m/s. Particle impact angles and velocities were predicted on the SIJ sample surface using computational fluid dynamics (CFD) to improve the understanding of how particle impingement contributes to erosion-enhanced corrosion and corrosion-enhanced erosion. Corrosion-enhanced erosion accounted for up to 20% of total erosion-corrosion degradation, with focused ion beam scanning electron microscopy (FIB-SEM) analysis showing that removal of work hardened layers and subsurface cracking were causes of enhanced degradation. Erosion-enhanced corrosion was not significant in the conditions tested.

Erosion–corrosion interaction of Fe–B alloy in flowing zinc

The effect of erosion angle on the erosion–corrosion interaction of Fe–3.5 wt-%B alloy in flowing zinc was investigated. The total erosion–corrosion rate decreased linearly, whereas the pure erosion rate fluctuated slightly with increasing erosion angle, which was strongly dependent on the erosion–corrosion interaction. At an erosion angle of 0°, liquid zinc corrosion damaged the sample surface and facilitated erosion, which in turn increased corrosion via the removal of corrosion products. As the erosion angle increased, corrosion products accumulated and Fe2B flaked and cracked in front of the erosion interface, which resulted, in turn, in increased obstruction to the diffusion of liquid zinc. Accordingly, the erosion–corrosion interaction was reduced, thereby resulting in a low material loss at high erosion angles.

Effect of 0.3 wt.% Al Addition in Flowing Liquid Zinc on the Erosion-Corrosion Behavior of Fe-3.5 wt.% B Alloy

The effects of 0.3 wt.% Al added to flowing liquid zinc on the corrosion inhibition and erosion-corrosion interfacial characteristics of Fe-3.5 wt.% B alloy were investigated in order to separate the pure erosion rate from the total erosion-corrosion rate and further study the erosion-corrosion interaction created by flowing zinc. The result indicated that the erosion-corrosion rate increased slowly and then sharply thereafter, while the corrosion-inhibition rate increased linearly and slowly at a bath temperature of 460-550 °C. The corrosion-inhibition efficiency of 0.3 wt.% Al addition in the flowing liquid zinc bath was significantly reduced and then enhanced with increasing bath temperatures, depending on the interfacial microstructures after Al-corrosion inhibition. A uniform and continuous Fe2Al5Zn x inhibition layer, which suppressed the corrosion reaction of iron and zinc, formed on the erosion-corrosion interface of the Fe-3.5 wt.% B alloy, thereby reducing the spallation of anticaustic Fe2B skeleton. Moreover, the gradual deterioration of the inhibition layer led to a reduction in the corrosion-inhibition ability. The present results indicate that, due to the beneficial Al-corrosion inhibition effect, the corrosion-inhibition rate as the pure erosion rate of Fe-3.5 wt.% B in flowing liquid zinc can be well separated from the erosion-corrosion rate by adding 0.3 wt.% Al to flowing liquid zinc bath.

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

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”.

Some recent advances in the development of theoretical approaches for the construction of erosion–corrosion maps in aqueous conditions

Significant progress has been made in the development of methodologies for the construction of erosion–corrosion maps for erosion by solid particles in aqueous conditions. Mathematical models for solid particle erosion have been combined with those for aqueous corrosion, enabling regime transitions to be identified as a function of the main process parameters. The effects of both erosion and corrosion variables have been identified on the maps. An important issue in such work has been the wide range of variables involved in the erosion–corrosion process. This has been addressed through combining such parameters into dimensionless groups. The results indicate that, although there are some limitations with such an approach, the technique does present some important advantages in dealing with the large number of variables associated with a single erosion–corrosion interaction. This paper describes some new developments on the above work, and indicates how the erosion–corrosion transitions, for pure metals and steels, can be described on a single map. Future directions of the work are also addressed.

Computer simulation of erosion-corrosion interactions at elevated temperatures

Computer simulation of erosion-corrosion interactions at elevated temperatures

Computer simulation of erosion-corrosion interactions at elevated temperatures

Although there have been some attempts to model erosion by solid particles at elevated temperatures, there have been few efforts to develop a model which can generate images of the surface morphologies in the various erosion-corrosion regimes. Many classifications of erosion-corrosion regimes have been identified and there is evidence that there are at least three such regimes. The physical significance of the surface in such regimes may be difficult to visualize, particularly when the situation is neither “erosion-dominated” (erosion of the substrate) nor “corrosion-dominated” (erosion plays a minor role compared with corrosion). The object of this research has been to develop a physical model to simulate the transitions between erosion--corrosion regimes at elevated temperatures. Properties of the particle (shape, size, velocity, hardness, flux), the target (corrosion resistance, hardness, impact angle) and the environment (gas composition and temperature) are considered in the model. The results are then used to construct a computer-generated image of the eroding surface. This paper describes the physical basis of the model and shows how the transitions between the regimes can be achieved by variation of the erosion and corrosion parameters. Typical results are shown and compared with existing erosion-corrosion data. The future development of the research is outlined in terms of the application to other environments in which erosion-corrosion occurs.

Relationship between the effects of velocity and alloy corrosion resistance in erosion-corrosion environments at elevated temperatures

Erosion-corrosion by either solid particle or liquid impact occurs in a wide variety of industrial environments which range from coal conversion processes to steam turbines in nuclear power generation. The effects of erosion-corrosion depend on properties of the particle, the target and the nature of the corrosion environment. Various regimes of erosion-corrosion interaction have been identified, ranging from “erosion-dominated” (erosion of the substrate) to “corrosion-dominated” (erosion of the corrosion product). In studies of erosion-corrosion, the effects of impact velocity are generally not well understood. In some environments in which corrosion occurs, high velocity exponents have been reported, while, in others, the values are close to 1. In addition, the effects of alloy corrosion resistance in environments of different velocities have been puzzling with differences in the exponents reported, as alloy corrosion resistance is increased. This paper considers the effect of velocity for various erosion-corrosion studies from the literature. The effects of alloy corrosion resistance for such results are evaluated. Some general provisos for the interpretation of the effects of velocity will be made for alloys of different corrosion resistance in erosion-corrosion environments. It is shown that relative erosion-corrosion resistance of alloys in one environment cannot be used arbitrarily to predict resistance in other environments, particularly if parameters such as velocity are varied significantly.