K.A. Yasakau

Lanthanide Salts as Corrosion Inhibitors for AA5083. Mechanism and Efficiency of Corrosion Inhibition

The inhibition effect of trivalent lanthanide (Ce 3+ , La 3+ ) cations toward the localized corrosion of 5083 aluminum alloy in chloride-containing solutions was investigated in the present work. Electrochemical impedance spectroscopy was employed to estimate the inhibition efficiency of the lanthanide species under study. Scanning Kelvin probe force microscopy was used to provide deeper understanding of the corrosion and inhibition mechanisms at the micro level. The results of electrochemical tests demonstrate effective hindering of the localized corrosion attack due to precipitation of highly insoluble deposits on cathodic intermetallics. Trivalent lanthanum cations confer a more effective corrosion inhibition in comparison to that of Ce 3+ . Superior inhibition of La 3+ resulted from the formation of very dense hydroxide domes while cerium-based precipitates have a porous granulated structure.

Active corrosion protection coating for a ZE41 magnesium alloy created by combining PEO and sol–gel techniques

An active protective coating for ZE41 magnesium alloy was produced by sealing an anodic layer, loaded with 1,2,4-triazole, with a sol–gel film. An anodic oxide layer was formed using PEO in a silicate–fluoride alkaline solution. This thin (1.8 μm) porous PEO layer was impregnated with corrosion inhibitor 1,2,4-triazole and sealed with a silica-based sol–gel film modified with titanium oxide. For the first time it was demonstrated that this relatively thin PEO-based composite coating revealed high barrier properties and provided superior protection against corrosion attack during 1 month of continuous exposure to 3% NaCl. A scanning vibrating electrode technique showed a sharp decrease (100 times) of corrosion activity in micro defects formed in the 1,2,4-triazole doped composite coating, when compared to blank samples.

Active Corrosion Protection by Nanoparticles and Conversion Films of Layered Double Hydroxides

The active corrosion protection of metallic substrates can be achieved by the addition of corrosion inhibitors to protective coatings. However, direct mixing of inhibitors with coating formulations...

Smart self-healing coatings for corrosion protection of aluminium alloys

Abstract: The main subject of this chapter is the application of smart, self-healing coatings for the protection of aluminium alloys against corrosion. The chapter begins by providing an introduction to the types of aluminium alloys used in industry and the problems, which face these alloys when they are exposed to a corrosive environment. Current strategies for protection against corrosion are discussed. Information on the different protective systems that do not possess intelligent inhibitive abilities, such as inorganic, hybrid organic–inorganic and polymeric coatings, are comprehensively presented and examined from the point of view of their applications, performance and drawbacks. The chapter also critically reviews different smart protection systems with controlled inhibitor release, based on pH permeable polymers, polyelectrolytes and biopolymers and coatings with ‘smart’ micro- and nanocontainers. The chapter concludes with a final discussion of the current and future protective systems for the prevention of corrosion in aluminium alloys.

Self-healing nanocoatings for corrosion control

Abstract: This chapter provides an overview of nanotechnology-based self-healing coatings. Different perspectives on the self-healing concept are presented and discussed in detail, with particular relevance for different trends in terms of coating technology. The chapter starts with an introduction on the self-healing concept, followed by a short description of different self-healing coatings. The detailed discussion of anticorrosion coatings begins with systems traditionally used in corrosion protection, including corrosion conversion coatings. Then, different self-healing systems consisting of surface treatments based on silane coatings, sol–gel coatings with nanoreservoirs and conductive polymers are reviewed in detail. The type, specific applications, performance and associated protection mechanisms are critically discussed in the context of their promising utilization as corrosion protective systems in real-life applications.

Study of the Corrosion Mechanism and Corrosion Inhibition of 2024 Aluminum Alloy by SKPFM Technique

Aluminum alloys have found many applications in different branches of industry. In spite of the valuable properties, there is a significant drawback because of the strong corrosion susceptibility, especially in chloride-containing medium. The present work is focused on study of the 2024 aluminum alloy corrosion mechanism on early stages using Scanning Kelvin Probe Force Microscopy (SKPFM). The corrosion impact was studied measuring the Volta potential (VP) and topography of alloy matrix and S-phase intermetallics after immersion in different electrolytes and pH. It is shown that presence of the chloride anions in the electrolyte leads to increase of aluminum matrix potential for about 100 mV. This can be resulted from the adsorption of chloride ions and their incorporation into the native oxide layer changing semiconductive properties of the oxide. The zones surrounding the S-phase intermetallics are changed more significantly demonstrating higher increase of VP close to the inclusion. These regions are correlated with the increased oxygen content suggesting formation of thicker oxide layer due to local polarization. Addition of an inhibitor to electrolyte also leads to change in Volta potential that is reflected on lower corrosion impact of aggressive environment.

Role of intermetallics in corrosion of aluminum alloys. Smart corrosion protection

Abstract This chapter provides an outlook of the corrosion mechanisms of aluminum alloys emphasizing the role of the intermetallic inclusions in corrosion initiation, progress, and inhibition. Various types of aluminum alloys are briefly discussed in terms of their chemical composition, microstructure, and applications in industry. The chapter also presents current active and passive corrosion protection strategies for aluminum alloys. The principal role of inhibitors in active corrosion inhibition and corrosion self-healing of aluminum alloys is emphasized. In the end of the chapter, a critical review of different active self-healing coating systems containing corrosion inhibitors and nanocontainers with inhibitors applied on aluminum alloys has been presented. The limitations and perspectives of such approaches are also discussed.

Novel and self-healing anticorrosion coatings using rare earth compounds

Abstract: 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.

Brittle Coating Layers for Impact Detection in CFRP

The detection of possible impacts in carbon-fiber-reinforced plastic (CFRP) structures is important for the evaluation of structural integrity of CFRP. Sol–gel-based sensitive coatings for impact detection on CFRP substrates have been developed and investigated by University of Aveiro (UAVR). The coatings are based on hybrid sol–gel formulations with tunable mechanical properties, i.e., brittleness adjusted for a defined range of impact energy. This sensitive layer allows the identification and location of mechanical impacts under visible light and without supplementary tools or conditions for its detection. A systematic study was performed to enhance the coating response for the defined impact threshold. A set of different parameters such as composition, fillers, curing conditions, surface roughness, and chemistry of the surface were tested and optimized.

Two Thermodynamics-Based Approaches to Atomic Oxygen Sensing

Impact of atomic oxygen is a main factor responsible for enhanced oxidation and fast degradation of spacecraft and satellite construction materials in low earth orbits. Thus, information concerning atomic oxygen concentration is important for spacecraft designers and manufacturers. Many sensors have been developed to perform atomic oxygen concentration measurement. However, these sensors have important disadvantages: high power consumption, low reproducibility, limited lifetime, and large mass/size parameters. In the present work two new methods based on a thermodynamic approach are proposed, employing an enhanced chemical potential of atomic oxygen. The first method is based on measurement of maximal temperature of silver oxidation in atomic oxygen, since this temperature depends on the concentration of oxygen in atmosphere. The second method is based on a Nernstian-type sensor with oxygen-conducting solid electrolyte. The electromotive force of this cell also depends on the concentration of atomic oxygen in the gas phase. Thermodynamic interpretations of sensor operation are proposed. The results of laboratory experiments on atomic oxygen pressure estimation by both methods are in good agreement. A new complex sensor using both approaches in one device is developed.