Corrosion
1) Thermal spray stainless steel coatings for hydroelectric turbines
Hydroelectricity is a competitive source of renewable energy due to its relatively low cost and flexibility. Some Canadian hydropower facilities have been in service for over 100 years, where recent advances in erosion mitigating technologies such as thermal spray coating techniques have been responsible for the extended performance beyond the equipment’s expected lifetime. While the erosion resistance of such hydraulic machinery has been improved, water contamination and infiltration can lead to severe damage and reduced operating life. In collaboration with HydroQuebec, this project will focus on studying the corrosion properties of a spectrum of engineered coatings developed to address the corrosion and erosion degradation mechanisms of stainless steel thermal spray coatings.
Experimental investigations
The base material for this project is a titanium and niobium stabilized ferritic stainless steel with low nickel content, which has been chosen from an economical perspective and due to its impressive stability in aqueous environments. It is well known that stainless steel is susceptible to localized corrosion, which originates from local inhomogeneities on the micron scale that lead to local electrochemical differences at the metal’s surface. Therefore one of the objectives of this project is to investigate the microstructural influence on corrosion properties of stainless steel thermal spray coatings in-situ using ultra microelectrodes and the scanning probe technique scanning electrochemical microscopy. SECM can be used in numerous modes, where the two of particular interest to this project include substrate generation/ tip collection (SG/TC) mode and feedback mode. The micro corrosion results will be complemented with bulk corrosion measurements such as potentiodynamic polarization measurements and electrochemical impedance spectroscopy and corrosion initiation sites will be studied ex-situ.
The base material for this project is a titanium and niobium stabilized ferritic stainless steel with low nickel content, which has been chosen from an economical perspective and due to its impressive stability in aqueous environments. It is well known that stainless steel is susceptible to localized corrosion, which originates from local inhomogeneities on the micron scale that lead to local electrochemical differences at the metal’s surface. Therefore one of the objectives of this project is to investigate the microstructural influence on corrosion properties of stainless steel thermal spray coatings in-situ using ultra microelectrodes and the scanning probe technique scanning electrochemical microscopy. SECM can be used in numerous modes, where the two of particular interest to this project include substrate generation/ tip collection (SG/TC) mode and feedback mode. The micro corrosion results will be complemented with bulk corrosion measurements such as potentiodynamic polarization measurements and electrochemical impedance spectroscopy and corrosion initiation sites will be studied ex-situ.
Schematic of a microstructural investigation using SECM.
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Mathematical modelling
Methods development
Laboratory measurements of corrosion rate are extremely dependent on the environmental (electrolyte, pH) and experimental (scan rate, potential range) conditions employed. ASTM standards provide a basis for designing experiments, but do not cover all cases -- comparing experiments in a systematic way is still a major challenge in the field. Our group uses finite element simulation to understand the effect of varying these conditions on the corrosion properties of a material in order to understand its overall behaviour. This involves describing what’s going on during a given measurement: the kinetics of reaction at the surface, the diffusion of species through the solution and passive film found on many metals, and the effect of material geometry on both of these. The underlying differential equations describing these systems can then be solved using finite element software such as COMSOL Multiphysics.
Recently, we have developed a finite element model for decoupling the contributions of mass transfer and activation to polarization curves, a technique commonly used to examine the mechanism of reaction as well as determine both the corrosion rate and potential of a sample. This model applies to a broad material scope, including both corrosion-susceptible magnesium alloys and corrosion-resistant stainless steels.
Methods development
Laboratory measurements of corrosion rate are extremely dependent on the environmental (electrolyte, pH) and experimental (scan rate, potential range) conditions employed. ASTM standards provide a basis for designing experiments, but do not cover all cases -- comparing experiments in a systematic way is still a major challenge in the field. Our group uses finite element simulation to understand the effect of varying these conditions on the corrosion properties of a material in order to understand its overall behaviour. This involves describing what’s going on during a given measurement: the kinetics of reaction at the surface, the diffusion of species through the solution and passive film found on many metals, and the effect of material geometry on both of these. The underlying differential equations describing these systems can then be solved using finite element software such as COMSOL Multiphysics.
Recently, we have developed a finite element model for decoupling the contributions of mass transfer and activation to polarization curves, a technique commonly used to examine the mechanism of reaction as well as determine both the corrosion rate and potential of a sample. This model applies to a broad material scope, including both corrosion-susceptible magnesium alloys and corrosion-resistant stainless steels.
Comparison of a simulated to experimental polarization curve.
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First principles modelling
High-performance corrosion-resistant materials often make use of heavily alloyed substrates with multi-component coatings. In complicated systems of this nature, understanding the contribution of each component is crucial to understanding and predicting its behaviour. Laboratory measurements are taken over a period of hours or days, but manufacturing targets are based on performance over a period of years or decades. Bridging this gap requires predictive simulation, the accuracy of which depends on the level of detail involved.
Our group uses a first principles understanding of the thermodynamics and kinetics of corroding systems in order to predict material behaviour as a function of material composition. Recently, we have used Pourbaix diagrams as a basis for simulating the corrosion of iron-based systems as a function of potential and pH. Further objectives of this project are to build up a detailed, systematic view of a high-performance coated alloy in order to accurately predict its behaviour under a variety of conditions.
High-performance corrosion-resistant materials often make use of heavily alloyed substrates with multi-component coatings. In complicated systems of this nature, understanding the contribution of each component is crucial to understanding and predicting its behaviour. Laboratory measurements are taken over a period of hours or days, but manufacturing targets are based on performance over a period of years or decades. Bridging this gap requires predictive simulation, the accuracy of which depends on the level of detail involved.
Our group uses a first principles understanding of the thermodynamics and kinetics of corroding systems in order to predict material behaviour as a function of material composition. Recently, we have used Pourbaix diagrams as a basis for simulating the corrosion of iron-based systems as a function of potential and pH. Further objectives of this project are to build up a detailed, systematic view of a high-performance coated alloy in order to accurately predict its behaviour under a variety of conditions.
E. D. Verink, Jr. Simplified Procedure for Constructing Pourbaix Diagrams in Uhlig 's Corrosion Handbook, Second Edition, (Ed. R. Winston Revie), 2000, John Wiley & Sons, Inc., Hoboken, NJ, USA, pp 111 - 124
Pourbaix diagram of iron.
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2) Corrosion-fatigue behavior of 13Cr-4Ni steels for hydraulic turbines
Quebec has a considerable high-voltage transmission system of hydropower, able to carry electricity across the country from mostly northern hydro dams towards southern demand centers. Hydro-Quebec’s production fleet is composed of more than 350 hydraulic turbines, which when in use can undergo damages from a combination of fatigue, cavitation, and corrosion synergistic effects, reducing the operating life time of materials.
Based on this, the current project (Fatco – Fatigue-Corrosion International Research Project) involves Canadian and Italian universities and industries, and is focus on the understanding of such synergistic effect aiming at the comprehension of the degradation mechanism of cast stainless steel and fatigued steel. Moreover, the corrosion and fatigue properties will be quantified and studied, as well as models will be developed to allow the prediction of fatigue-corrosion. With this evaluation, all the partners involved in this project will have benefits of improving their attenuating corrosion approach to provide long term sustainability of their infrastructure.
Based on this, the current project (Fatco – Fatigue-Corrosion International Research Project) involves Canadian and Italian universities and industries, and is focus on the understanding of such synergistic effect aiming at the comprehension of the degradation mechanism of cast stainless steel and fatigued steel. Moreover, the corrosion and fatigue properties will be quantified and studied, as well as models will be developed to allow the prediction of fatigue-corrosion. With this evaluation, all the partners involved in this project will have benefits of improving their attenuating corrosion approach to provide long term sustainability of their infrastructure.
SEM images of a 13Cr-4Ni steel undergoing localized corrosion.
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3) Scanning electrochemical cell microscopy investigations of aluminum alloys
This project will correlate the surface structure of aluminum alloys to their local corrosion properties. This will use the scanning electrochemical cell microscopy, which can extract spatially resolved electrochemical information on the micrometer scale. In this method, a microscale electrochemical cell is formed by approaching a pipette filled with electrolyte to bring it into contact with the alloy surface through the microdroplet at the end of the pipette. At each landing site we can conduct polarization measurements.
Using these landing sites, we can explore the surface heterogeneities of the alloy including intermetallic spots, grain boundaries, pits, crevices and so on. In this way, we can build up images reflecting the local corrosion properties which are correlated to the underlying alloy microstructure.
Using these landing sites, we can explore the surface heterogeneities of the alloy including intermetallic spots, grain boundaries, pits, crevices and so on. In this way, we can build up images reflecting the local corrosion properties which are correlated to the underlying alloy microstructure.
Recent group publications
- Grandy, L.; Lacasse, R.; Adsetts, J.; Hitz, C.; Chhin, D.; Mauzeroll, J. Observation of natural convection and particle ejection from stainless steel single pits. Corrosion Science. 2024. 241, 112518
- Grandy, L.; Yassine, S.; Lacasse, R.; Mauzeroll, J. Selective Initiation of Corrosion Pits in Stainless Steel Using Scanning Electrochemical Cell Microscopy. Analytical Chemistry. 2024. 96, 19, 7394-7400
- Grandy, L.; Mauzeroll, J. Localizing the electrochemistry of corrosion fatigue. Current Opinion in Colloid & Interface Science. 2022, 61, 101628