One of the main applications of SVET in corrosion research is the study of the corrosion inhibition effectiveness and the evaluation of the self-healing effect of inhibitor-containing coatings. The tip of the platinum/iridium vibrating electrode is electroplated with black platinum, which creates a large electrode surface and confers high capacitance to the tip. When studying organic inhibitors in aqueous solutions with SVET, inhibitor adsorption may occur at the tip, causing its contamination and the initial calibration conditions of the system might not be valid. This may lead to an incorrect interpretation of the results. This work is intended to study the effect of different inhibitors (cerium nitrate, 8-hydroxyquinoline, potassium 2,5-dimercapto-1,3,4-thiadiazolate, benzotriazole and mercaptobenzothiazole), typically used for corrosion protection of aluminum alloys, on the Pt probe signal during SVET measurements. The results reveal the detrimental effect of some corrosion inhibitors on the sensitivity of the vibrating probe, an effect that imposes a regular assessment of the electrode state during measurements. The increase of the signal noise was related to a decrease of the probe capacitance, while the false current density signal was a result of the potential drift between vibrating and reference electrodes.@en

Integrated attenuated total reflection – Fourier transform infrared spectroscopy (ATR-FTIR) – Electrochemical impedance spectroscopy (EIS) measurements were used to simultaneously follow chemisorption mechanisms of organic inhibitors as well as their corrosion inhibition efficiency towards magnesium based substrates. Four carboxylic compounds, i.e. 2,5-pyridinedicarboxylic acid (PDC), 3-methylsalicylic acid (MSA), sodium salicylate (SS) and fumaric acid (FA), were selected based on their promising inhibiting capacities and were all shown to chemisorb at the MgO/Mg(OH)2 surface by carboxylate bond formation. Orientation analysis using polarized infrared light showed that carboxylate bonds established using aliphatic carboxylate compound aligned perpendicular to the magnesium surface, whereas carboxylate bonds with aromatic compounds were oriented in plane with the magnesium surface. This different orientation is associated to the involvement of π-interactions in the MgO/Mg(OH)2 – aromatic carboxylate adsorption. Additionally, DFT calculations revealed that the addition of hetero-atoms (i.e. N or OH) in the molecular structure contributes to increased adsorption energies, indicating that next to carboxylate groups also these hetero-atoms are involved in interfacial interactions. Integrating the ATR-FTIR setup with an electrochemical cell allowing for simultaneous EIS measurements lead to two surface phenomena determining the inhibition efficiency. Surface hydroxylation processes on one hand forming a MgO/Mg(OH)2 layer on one hand, and the chemisorption of carboxylate compounds on the other hand. The inhibition efficiency was found to increase in following order: FA < PDC < MSA and was mainly associated to the formation of a MgO/Mg(OH)2 layer. SS was shown to act as a corrosion accelerator rather than a corrosion inhibitor. Despite its high sensitivity for water, both surface processes could be followed in situ by means of ATR-FTIR. Simultaneously, protective properties of the formed films could be quantified by means of EIS. Consequently, integrated ATR-FTIR – EIS methodology has shown to be highly valuable for gaining in-situ insights in the inhibition mechanism, while quantifying the inhibition efficiency. This was even possible for highly active metal substrate as magnesium, although further developments are suggested if one aims to quantify electrochemical constants related to corrosion and other surface processes measured at the low frequencies (i.e. < 1 Hz).@en

Self-healing materials have the ability to repair themselves and recover functionality after degradation, damage and failure. This chapter reviews recent developments in self-healing protective coatings which contain rare earth-based inhibiting compounds for active corrosion protection of metals. These new 'green' inhibitors are being developed as substitutes for chromate-based inhibitors. Different types of organic, hybrid and metallic systems are considered, with particular emphasis on thin sol-gel based layers. The main strategies for encapsulation of RE inhibitors are also reviewed. Significant future effort is required to improve the properties of organic coatings and to explore new self-healing coating alternatives that allow controlled release of the inhibitor.@en

This book is about reviewing and exploring the opportunities for introducing increased functionality into coating systems. The intention is to not only provide an account of recent developments, such as other books of this genre, but to also review, in detail, the nature of the problems that we are trying to address in advancing the materials science of coating systems. To this end we examine the fundamentals of corrosion science, the materials science of coatings, and developments in characterisation methods that all help to give an overview of the field. Importantly, we also look at the needs of industry with respect to developments in the coatings field.@en

This book is about reviewing and exploring the opportunities for introducing increased functionality into coating systems. The intention is to not only provide an account of recent developments, such as other books of this genre, but to also review, in detail, the nature of the problems that we are trying to address in advancing the materials science of coating systems. To this end we examine the fundamentals of corrosion science, the materials science of coatings, and developments in characterisation methods that all help to give an overview of the field. Importantly, we also look at the needs of industry with respect to developments in the coatings field.@en