Surfaces and Interfaces II: Materials-related Electrochemistry, Chemical Reactivity and Applications

Abstract

Introduction to fundamentals of (electro)chemical surface processes on conducting materials: reactivity, degradation, functionalising and deposition. Relevant oxidation/corrosion mechanisms are presented al-ways in relation with suitable characterisations (focus: electrochemical & surface analytical methods) and data analysis. Characterisation of (thin film) metal oxides are also addressed.

Objective

The students should learn and understand the fundamental "electro"chemical reaction mechanisms responsible for the most important corrosion phenomena affecting "classical" industrial relevant metals/alloys and they should know the limitation in the use of these "standard" materials in aggressive environments. They should be able to explain in detail the degradation mechanisms of Stainless Steels and Aluminium alloys always presented as typical reference materials for the different corrosion types during the lecture. Moreover, and more importantly, they should then be able to transfer this acquired knowledge about electrochemical reactions, corrosion mechanisms and surface functionalising directly in the developments phase of very different new materials/coatings. This know-how is essential in order to minimise the corrosive failure risks and increase the sustainability/durability of new industrial products. Finally, and as most important asset of the lecture, they should know how to approach a corrosion problem/failure and be able to propose the right characterisation techniques/methodology to investigate each specific corrosion problems. For this purpose, the extended lecture now sets a stronger emphasis on electrochemical processes description and understanding with special topics dedicated to experimental data analysis (the NOVA soft-ware will be made available to the registered students to perform data analysis) and also on thin surface oxide characterisation. These defective amorphous oxides with different properties than the bulk crystal-line ones play a key role in surface reactivity but also on surface protection.

Content

The most important types of corrosion mechanisms will be presented and discussed during the different lectures. The semester will start with some short basics about thermodynamics and reaction kinetics. Afterwards and for each specific corrosion phenomenon, the most relevant experimental characterisation method will always be introduced directly in relation with explanations about the corrosion mechanism. This combination allows the student to couple theoretical physico-chemical concepts with practical characterisation methodologies used in corrosion research. It also indicates the most relevant methodologies to answer each of the stages of a degradation process. Following topics will be presented (mechanism/method used): - Thermodynamics related to corrosion processes prediction - Corrosion reaction kinetics / DC electrochemical methods - Passivation and passive film properties / XPS (X-Ray Photoelectron Spectroscopy) and EQCM (Electro-chemical Quartz Crystal Microgravimetry) - Uniform corrosion/Electrochemical Impedance Spectroscopy (EIS) with the example of Magnesium biocorrosion - Galvanic corrosion/AFM-SKPFM (Atomic Force Microscopy based Scanning Kelvin Probe Force Microscopy) - Related electrochemical processes on metallic materials: electropolishing, electrodeposition and electrophoretic deposition - Localized corrosion initiation (pitting)/ Microcapillary cell technique - Photoelectrochemistry and Crevice corrosion with description of specific electrochemical setups - Intergranular corrosion and mathematical modelling concepts / Microtomography - Stress corrosion cracking (SCC) / corrosion-fatigue - Selected examples of functional anodic oxide growth and more "exotic" corrosion mechanisms (Si, Ag, Ta, a.s.o), corrosion protection and surface functionalising will be presented at the end if times permit The special topics lecture will also contain three focusses: 1) One part directly linked to the core lecture with a stronger focus on electrochemical data treat-ment/analysis session a. With classical exercises always related to methods presented during the core lecture b. The lecturer will then also introduce various software for thermodynamic calculation and for electro-chemical measurements. The software will previously be made available to the students, and they will re-ceive small assignments to solve and present/discuss during the lecture c. "Advanced" topic: Biocorrosion and the metal(oxide)-biology interface topic will be introduced as an important field where interaction/corrosion mechanisms are still poorly understood 2) Presentations from industry representatives on selected surface treatment techniques of steel, including related analytical methods and examples of corrosion failure analysis and mitigation (2x2 hours on Thursdays). 3) In alternants on Thursdays, a detailed description of thin oxide (very relevant to passivation and bio-corrosion mechanisms) and their reactivity/characterisation will be presented. The lecture will start with a description of various oxide growth methods: a. General short introduction about oxide deposition methods b. Anodizing/electro-deposited oxides c. Thermal oxidation (oxidation and reduction kinetics, e.g. Cu) And continue with the various characterisation of thin amorphous/defective oxides by: d. Ellipsomety, advanced XRD analysis (pair distribution) e. Stress analysis (Digital image correlation, stress curvature) f. Rutherford Backscattering / ERDA g. Raman/FTIR h. HAXPES – chemical state analysis i. Synchrotron (EXAFS, XANES) and neutron methods j. Photoluminescence Each methodology is supported by presentation of research and applications examples (mainly Al, Ti, Si, Ta, Hf, etc).

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