Search results for "CORROSION"

Electrochemical Age Determinations of Metallic Specimens—Utilization of the Corrosion Clock

2019

Dating needs an age-dependent phenomenon (a "clock"), a procedure for monitoring the advance of time by measuring a physicochemical quantity, and, in the case of archeological artifacts, a sampling procedure that guarantees the representativity and integrity of the dated objects. Metal corrosion in an aerobic atmosphere is a phenomenon whose advance can in principle be used as a clock that depends on the environmental conditions. In spite of the limitation imposed by differences in local conditions of corrosion, a new approach for age determinations has been developed and applied as a feasible tool for age determinations of metallic specimens studied by archeologists and historians. These t…

The use of the Pearson’s correlation coefficients to identify mechanical-physical-chemical parameters controlling the tribocorrosion of metallic alloy

2021

Abstract Tribocorrosion is of complex nature as it involves multiscale interactions between mechanical, (electro-)chemical, physical, and material factors. A methodology based on the use of the Pearson’s correlation matrix and local techniques is described here to analyze interactions between these factors. The most influent experimental parameters selected for tribocorrosion tests on the surface/subsurface characteristics and on the corrosion parameters are identified. Correlations between surface/subsurface and corrosion parameters are also analyzed to propose criteria and to understand basic mechanisms of tribocorrosion. This methodology is particularly useful in the case of multiphase m…

Influence of aeration on the localized trenching on aluminium alloys

2010

This paper aims to make the difference between alcalinisation and micro-galvanic corrosion in the mechanism of the corrosion of Al alloys. Using a pH microprobe, the pH changes inside a pure water droplet deposited on a thermal aged 2011 aluminium alloy were scanned. These pH variations, depending on the position inside the droplet, were related to the heterogeneous corrosion attacks of the aluminium surface quantified by AFM measurements. A modelling investigation is proposed to evaluate the distinct roles of alcalinisation, due to the oxygen reduction reaction (ORR), and the galvanic coupling between intermetallic particles and the surrounding matrix. It can be concluded that the former c…

Application of total internal reflexion fluorescence microscopy for studying pH changes in an occluded electrochemical cell: Development of a wavegui…

2006

A device for pH mapping derived from optical sensors similar to total internal reflection fluorescence microscopy (TIRFM) has been developed for future possible applications in the field of localized corrosion. The sensing principle is the increase of the fluorescent yield of the fluorescein with the pH of the medium. The basic principle of this sensor is based on the excitation of a fluorescent silica polymer film of nanometre dimensions, deposited by sol–gel method on a waveguiding layer. The total internal reflexion conditions creates an evanescent wave which interacts with the molecules trapped in the silica layer. A conventional microscope located above the sample collects the fluoresc…

Origin of Ubiquitous Stripes at the Graphite–Water Interface

2020

The investigation of solid-liquid interfaces is pivotal for understanding processes like wetting, corrosion, and mineral dissolution and growth. The graphite-water interface constitutes a prime example for studying the water structure at a seemingly hydrophobic surface. Surprisingly, in a large number of atomic force microscopy (AFM) experiments, well-ordered stripes have been observed at the graphite-water interface. Although many groups have reported on the observation of stripes at this interface, fundamental properties and, in particular, the origin of the stripes are still under debate. Proposed origins include contamination, interplanar stacking of graphene layers, formation of methan…

Ultimate Shear of RC Beams with Corroded Stirrups and Strengthened with FRP

2019

Transverse reinforcement plays a key role in the response behavior of reinforced concrete beams. Therefore, corrosion of steel stirrups may change the failure mode of elements from bending to shear, leading to a brittle and catastrophic crisis. It is important to strengthen reinforced concrete beams with corroded stirrups to enhance the shear resistance. This paper presents a formulation, based on the modified compression field theory, to estimate the ultimate shear of reinforced concrete beams strengthened with FRP, because of stirrup corrosion. The detrimental effect of corrosion on steel stirrup yield strength was taken into account by introducing an empirical decay law. The effective st…

In-vitro-Studie der Interferenz von kieferorthopädischer Bebänderung und Füllungswerkstoffen

1992

Discoloring and layers on bands and restorations during fixed orthodontic therapy are well known clinical phenomenon. Because of the complexity of etiological factors an in-vitro model was used in this study. Aim of the study was to examine the amounts and sort of metals which are dissolved. Therefore, respectively 25 normed MOD-cavities in Frasaco-teeth were filled with a non-gamma-2-amalgam (Amalcap plus, Vivadent) and condensed manually or mechanically. In addition, ten crowns of a high golden (Maingold SG, Heraeus) as well as a palladium basis alloy (Albabond A, Heraeus) were casted. Then they were banded with stainless steel bands (Dentaurum) and cemented with a glass ionomer cement (K…

Mott-Schottky analysis of differential capacitance data of passive-film electrolyte junctions. Is it really providing correct physical insights on th…

2009

Semiconductor electrochemistry approach to passivity and passivity breakdown of metals and metallic alloys

2004

AbstractA critical appraisal of the use of the theory of semiconductors in characterising passive films on metals and alloys is provided, with special emphasis on the use of Mott-Schottky theory for the location of characteristic energy levels of the passive film-electrolyte junction. Some inconsistencies between theory and experimental results in the case of thin passive films are discussed together with possible alternative ways for overcoming such problems. The role of semiconducting properties in determining the pitting behaviour of passive films on W in solutions containing halide is presented and discussed. The validity of a recently proposed correlation between the solid state proper…

Non Linear Phenomena in Oxidation of Metals and Alloys

1991

Analyse de quelques exemples du comportement non conventionnel des couches de corrosion obtenues par oxydation ou sulfuration de certains metaux et alliages