Volume 29, Issue 1-2

Irradiation-assisted stress corrosion cracking (IASCC) refers to the process(es) by which irradiation enhances the inherent susceptibility of alloys to stress corrosion cracking (SCC). This article begins with an introduction to the IASCC problem experienced in light water reactors, followed by a summary of existing plant and laboratory data that reveal its dependence on irradiation, environment and alloy parameters. The specific effects of irradiation on IASCC are classified into two categories: the effects on water chemistry and the effects on microstructure. Water chemistry effects include radiolysis and its effects on corrosion potential, and effects of corrosion potential on IASCC. Microstructure effects include radiation- induced segregation (RIS), irradiated microstructure, swelling and creep, and hydrogen and helium generation. Leading mechanisms proposed to explain the role of radiation in the SCC process are: radiolysis and crack tip strain rate, grain boundary chromium depletion, irradiation hardening, localized deformation and RIS of minor elements. As nuclear power plants operate for longer, an increased incidence of SCC can be expected unless active mitigation steps are taken. Drawing on the accumulated understanding over the past four decades of the key processes believed to control IASCC, a set of attributes of an ideal, IASCC-resistant alloy are identified as a first step.

The determination of oxide thickness via cathodic reduction was developed in 1936. It is a simple laboratory practice that has the sensitivity and capability to analyze total oxide thickness of both cuprous and cupric oxides within the same run. Unfortunately, contradictory results and misidentification of oxide layers on the copper surface have caused ambiguity in the interpretation of many published results, leading to its incorrect use in industrial applications. This review surveys experimental parameters used by the authors, such as electrolyte composition and concentration, current density, current efficiency, sample history, inter­facial impedance, crystalline orientation, and concentration of depolarizer on the cathodic reduction of copper oxides. Ultimately, the goal of the review is to propose solutions by which more precise measurement and correct identification of oxide layers could be derived from this type of experiment.

Electro-chemical scanning probe microscope (EC-SPM) is one of the potential surface investigation techniques to study the electrode-electrolyte interface and over, the years, it has significantly contributed to the understanding of the physico-chemical phenomenon of electrochemical process in different electrochemical environments. The ability to probe the local character at the sub-microscopic level of electrode-electrolyte interfaces with potentiostatic control has advanced its applications in various fields of fundamental, and applied, research such as material science, biological science, physical and chemical science, in order to study the structure and dynamic properties of materials and interfaces. Included in such studies are the structure-reactivity of electrode surface, electro-deposition, surface reconstructions, absorption process, process of corrosion initiation, the study of biological substances in nearby physiological conditions and other interfacial surface morphological studies. Out of several interesting applications of EC-SPM, one of the important and interesting fields of study is the process of corrosion initiation of different materials in simulated environments. To date, its applications are wide spread for understanding passive film property, surface dissolution, surface morphological changes prior to corrosion initiation, the efficiency of inhibitors, and many other branches of corrosion science. As EC-SPM continues to play a significant role in comprehending the process of corrosion, it is important to keep up-to-date on the progress made in the recent past. Thus, the basic aim and scope of the present review is to provide the trends and status of corrosion research of various technologically important materials using EC-SPM. The review includes, an introduction to the fundamentals of EC-SPM, instrumententation in commercial equipments, and applications in the field of corrosion research of various technologically important materials in different electrochemical environments. Illustrative examples have been provided from several investigations reported in the field of electrochemical scanning probe microscopy towards addressing the most critical aspects of corrosion. Major emphasis has been given towards passivation, corrosion initiation, material protection using coatings and associated phenomenon. The review mostly focuses on morphological features of various investigations made so far; for more explanation and other allied experimental techniques readers are requested to go through the respective articles.

Fabrication and applications of self-organized TiO 2 nanotube arrays is briefly reviewed. This nanoscale material has attracted considerable attention owing to its potential in gas sensing, photo-thermal and photovoltaic conversion devices, photoelectrolysis and photocatalysis, etc. TiO 2 in nanowire form, nanotube form and other nanoporous structures is desirable because of its high surface–volume ratio, high surface activity and superior sensitivity. TiO 2 nanotubes and nanofibers have been developed by diverse techniques such as sol-gel, electrodeposition and anodization. In recent years, there has been significant progress in nano-structured TiO 2 fabrication using the anodization method. This consists of oxidation (corrosion) of titanium foils or titanium thin films deposited onto substrates (e.g., silicon), immersed in acid or neutral F - containing solutions. Significant interest has arisen in anodization parameters, such as applied potential, concentration and type of corrosive solutions, anodization time length and temperature. This parameters influence mechanical-structural, chemical and electrical features of porous TiO 2 . Recent work concerning fabrication, applications and growth models is described in this review paper.