Learn the Fundamentals of Corrosion Electrochemistry

By the end of this lecture, learners should understand the concept of potential difference and its practical application, recognize the significance of measuring potential difference between two points in electrochemical systems and comprehend the standard conditions and conventions for measuring standard potentials of reactions with respect to a standard hydrogen reference electrode.

By the end of this lecture, learners should understand standard electrode potential and its link to Gibbs free energy, recognize the significance of the electrochemical series in ordering metals by nobility and assessing corrosion driving forces, calculate standard potentials and potential differences between metals in solutions, and determine thermodynamic driving forces for corrosion in standard conditions. Additionally, they should appreciate the implications of corrosion-related reactions occurring on the same metal surface, particularly regarding the feasibility of cathodic reactions based on metal nobility.

By the end of this lecture, learners should have gained an understanding of key concepts related to electrochemistry. They should grasp the significance of the electrochemical series in providing standard potentials under specific conditions and how the Nernst equation, derived from thermodynamic principles, enables the calculation of equilibrium potentials in non-standard scenarios. Learners should also recognize the components and variables within the Nernst equation and be capable of applying it to determine equilibrium potentials based on given conditions, such as concentration. Furthermore, this lecture introduces the Nernst equation's relevance to Pourbaix diagrams, which correlate pH and equilibrium potentials in electrochemical systems.

By the end of this lecture, learners should understand how to use the Nernst equation to calculate equilibrium potentials in non-standard conditions and determine potentials for specific reactions like oxygen reduction and hydrogen evolution as pH varies. Learners should also appreciate the significance of Pourbaix diagrams, which illustrate the thermodynamic feasibility of reactions based on pH and potential, with a specific focus on the Pourbaix diagram for water. Additionally, they should be able to interpret these diagrams, identifying three regions that signify the stability of water, oxygen, and hydrogen species, particularly in the context of corrosion analysis. Lastly, learners should recognize the fundamental connection between the Nernst equation and Pourbaix diagrams .

By the end of this lecture, learners should have a comprehensive understanding of how to construct a Pourbaix diagram for a metal, using zinc as an illustrative example. They should recognize the practical significance of Pourbaix diagrams, particularly in the context of corrosion analysis, as these diagrams reveal which species are stable at varying pH and potential conditions. Additionally, learners should appreciate the distinctions between the immunity, corrosion, and passivity regions within a Pourbaix diagram and understand their implications for a metal's corrosion behavior. Moreover, they should be able to determine the possible cathodic reactions occurring during metal corrosion by overlaying the Pourbaix diagram of water onto that of the specific metal.

By the end of this lecture, learners should possess a solid understanding of the Pourbaix diagrams for copper, aluminum, gold, and iron. They should be able to interpret these diagrams to determine the regions of immunity, corrosion, and passivity for each metal. Specifically, learners should recognize the conditions under which each metal is thermodynamically stable or prone to corrosion based on pH and potential. Additionally, they should understand which cathodic reactions are thermodynamically possible during the corrosion of these metals and how the potential difference between these reactions varies with pH.

By the end of this lecture, learners should understand the representation of corroding surfaces in terms of electrical currents, grasp the relationship between anodic and cathodic currents, and recognize the significance of the corrosion current. Additionally, they should comprehend the issue associated with directly measuring corrosion currents during free corrosion. Furthermore, learners should be familiar with the concept of a three-electrode cell and how it allows for the study of surface responses to applied external currents. Lastly, they should recognize the role of a potentiostat in automating experimental control and data collection in electrochemical corrosion studies.

By the end of this lecture, learners should have gained an understanding of how applying electrical perturbations to electrode surfaces can impact electrochemical reactions, with a focus on single reactions. They should be familiar with the concepts of overpotential and exchange current, and how these relate to the kinetics of electrochemical processes. Learners should also have grasped the practical aspects of conducting experiments to measure current-potential relationships using potentiostats and three-electrode cells. Additionally, they should be able to interpret current-potential diagrams in both linear and semi-logarithmic scales, gaining insights into anodic and cathodic behaviors near and far from the equilibrium potential.

By the end of this lecture, learners should have a solid understanding of the kinetics of electrochemical reactions, particularly in scenarios involving charge transfer control. They should be familiar with the Butler-Volmer equation and its application in describing the relationship between current density, overpotential, and reaction kinetics. Additionally, learners should grasp how the Butler-Volmer equation simplifies near the equilibrium potential and for large overpotentials, leading to linear and exponential relationships, respectively.

By the end of this lecture, learners should have a comprehensive understanding of the kinetics involved in diffusion-limited reactions, focusing on the cathodic reaction of oxygen reduction. They should be able to explain how the diffusion of oxygen molecules to the metal surface can become the limiting step in this reaction. Furthermore, learners should understand the concept of concentration polarization and how it contributes to the total overpotential in cathodic reactions. They should be familiar with the oxygen limiting current and its representation in current density-potential plots, including both linear and semi-logarithmic scales.

By the end of this lecture, learners should understand the anodic kinetics of passive metals and how passivity leads to the formation of protective oxide films. They should be able to describe the key features of anodic polarization curves for passive metals, including the active-passive transition, passive region, and transpassive or pitting region at high potentials. Additionally, learners should grasp the factors influencing the behavior of passive metals at high potentials, such as oxide conductivity, metal ion oxidation states, and the presence of aggressive ions like chlorides. They should be able to differentiate between different phenomena, like pitting, oxygen evolution, and high-valence cation formation, based on observed current changes.

By the end of this lecture, learners should understand the fundamental concept of Evan's diagrams and how they are utilized to analyze the behavior of corroding electrodes experiencing multiple simultaneous reactions. These diagrams provide insights into corrosion processes, including the corrosion potential, corrosion current, and the role of Tafel coefficients. Additionally, learners should grasp the simplifications made when constructing Evan's diagrams, focusing on the relevant branches of anodic and cathodic reactions, and comprehend the significance of the position of the corrosion potential between equilibrium potentials in electrochemical systems.

By the end of this lecture, learners should have acquired the knowledge and skills needed to estimate the corrosion current in corroding electrodes when both the anodic and cathodic reactions are under activation control. They should understand two distinct methods for estimating the corrosion current: one involving the application of large polarizations and the other using small polarizations to measure polarization resistance. Learners should also be able to calculate the corrosion current using the Stern-Geary equation and have an appreciation of the advantages and limitations of each method.

By the end of this lecture, learners should understand how the kinetics of anodic and cathodic reactions influence the corrosion potential and corrosion current density in materials undergoing corrosion under activation control. They should grasp the concept that the presence of cathodically active phases can lead to increased cathodic activity, resulting in higher corrosion rates and higher corrosion potentials. Learners should also recognize that the corrosion potential alone is not a direct indicator of corrosion rate when comparing materials corroding independently, emphasizing the importance of considering specific kinetic factors to assess relative corrosion susceptibility. Additionally, they should be aware of the concept of galvanic corrosion, where electrical connections between materials can accelerate corrosion on the material with the lower corrosion potential.

By the end of this lecture, learners should have a clear understanding of how active corrosion, limited by the diffusion of oxygen, influences the corrosion behavior of materials. They should be able to identify the characteristics of such corrosion in potentiodynamic polarization curves, including the linear region in the anodic branch and the vertical region in the cathodic branch. Learners should also recognize that in this scenario, the corrosion current is primarily determined by the oxygen limiting current, with other factors having minimal impact. They should grasp the relationship between the availability of oxygen, corrosion current density, and corrosion potential, understanding that more oxygen results in higher corrosion rates and higher potentials. Additionally, learners should comprehend how the distribution of oxygen in different regions of a material can lead to localized corrosion, where regions with lower oxygen availability tend to corrode more than those with higher oxygen concentration.

By the end of this lecture, learners should understand the corrosion behavior of materials when both hydrogen evolution and oxygen reduction reactions occur at the corrosion potential. They should grasp how factors like experimental conditions, electrode composition, and oxygen concentration influence the dominance of these cathodic reactions and, consequently, the corrosion process. Additionally, learners should recognize how potentiodynamic polarization curves can provide insights into these corrosion mechanisms and learn to interpret cases where hydrogen and oxygen currents have comparable magnitudes near the corrosion potential, making precise corrosion current estimation challenging based solely on the cathodic branch of the curve.

By the end of this lecture, learners should understand the behavior of passive metals in corrosive environments. They should grasp the concept of active-passive transitions in the anodic behavior of passive metals, as well as the influence of cathodic reactions, such as hydrogen evolution and oxygen reduction, on the corrosion process. Additionally, learners should recognize how the relative positions of anodic and cathodic curves impact the corrosion rate and behavior of passive metals, as demonstrated through potentiodynamic polarization curves.

By the end of this lecture, learners should have a comprehensive understanding of the practical aspects of setting up a three-electrode cell for electrochemical measurements. They should recognize the key components of a three-electrode cell, including the working electrode, reference electrode, and counter electrode, and understand their roles in the electrochemical measurement process. Additionally, learners should grasp the importance of electrode area, the distance between the reference electrode tip and the working electrode surface, and the size and position of the counter electrode in optimizing cell performance. They should also be aware of variations in cell configurations, such as the use of luggin probes, separate compartments for the counter electrode, and double-chamber reference electrodes, and when and why these variations might be employed to address specific measurement requirements.

By the end of this lecture, learners should have a clear understanding of two crucial aspects in electrochemical measurements. Firstly, they should be proficient in converting potential measurements obtained using commercial reference electrodes (such as silver-silver chloride, calomel, or copper-copper sulfate) into potentials with respect to the hydrogen reference electrode, which serves as the standard for tabulated potential values. This involves understanding the concept of potential differences and how to add the potential of the commercial reference electrode to the experimental potential measurement with the correct signs.Secondly, learners should grasp the distinction between applying a set polarization with respect to the open circuit potential (corrosion potential) and applying it with respect to the reference electrode. They should be able to visualize this concept on a potentiodynamic polarization curve and understand how the choice of reference for polarization affects the interpretation of electrochemical measurements.

By the end of this lecture, learners should have a comprehensive understanding of the key parameters involved in setting up and conducting a potentiodynamic polarization measurement in electrochemistry. They will grasp the significance of factors such as the free corrosion time, starting and ending potentials, and sweep rate. This knowledge will enable them to make informed decisions when designing experiments, allowing for the acquisition of accurate and meaningful potentiodynamic polarization curves. Students will also appreciate the trade-offs and considerations when selecting these parameters, ensuring the reliability and relevance of their electrochemical measurements.

By the end of this lecture, learners should have acquired a fundamental understanding of linear polarization measurement as a non-destructive method for estimating corrosion currents. They will have learned how to set up and conduct linear polarization experiments, where small potential sweeps near the corrosion potential are employed to assess corrosion rate. Additionally, students will comprehend the relationship between polarization resistance, Stern-Geary coefficients, and corrosion current estimation. Learners will grasp the key parameters involved in linear polarization experiments, enabling them to design and perform accurate corrosion assessments.

By the end of this lecture, learners will have acquired knowledge about how electrolyte resistance impacts the shape of potentiodynamic polarization curves in electrochemical studies. They will understand that factors such as electrolyte resistivity and electrode spacing influence electrolyte resistance. Moreover, students will grasp the concept that electrolyte resistance introduces an ohmic overpotential, which increases proportionally with current density and becomes dominant at high currents when there's no diffusion limitation. This knowledge will enable them to recognize non-linear behavior in potentiodynamic polarization curves and the challenges it poses for graphical analysis, corrosion current estimation, and Tafel coefficient determination.