Search results for " corrosion"

Influence of an elastic stress on the conductivity of passive films

2001

Abstract The electrochemical impedance was measured over a large range of frequency and under straining condition in sodium chloride solution. The Mott-Schottky analysis, performed at high frequency, appears as very useful method to study the effect of an elastic stress on the capacitance values. The results obtained indicate that the semi-conductive properties of passive films formed on a type 316 L stainless steel (SS) are not markedly modified by an elastic stress when applied after ageing. In contrast, passive films formed in the presence of elastic stress have a higher donor and acceptor concentration than those formed in a stress-free state, suggesting that the passive film conductivi…

Droplet cell investigation of intergranular corrosion on AA2024

2017

An original method combining a droplet cell with direct optical interrogation of the reverse side of a 50μm thick foil AA2024 has been tested to evaluate the possible analysis of the current during intergranular corrosion tests. The foil microstructure and the selected orientation were suitable for recording the current generated during the propagation in volume of a well-defined grain boundary trace. Even if it is impossible to reach a charge and mass balance from these preliminary attempts, it was demonstrated that it is possible, despite hydrogen evolution, to record a current transient resulting from the full penetration of an intergranular path. Keywords: Intergranular corrosion, Alumi…

Influence of bond deterioration on shear-flexure failure of prestressed girders with post-tensioned tendons

2021

Internal prestressing with bonded tendons suffers corrosion of wires and bond deterioration due to the bad infill of grouted sheaths. Many bridge girders show this state through cracking, deflections and in the worst cases, sudden failures. In Italy these are common situations, and the internal tendon corrosion is among the major causes of bridge degradation and damage, especially for grouted post-tensioned tendons. This paper presents the analysis of failure of prestressed cross-sections considering shear and flexure in the case of bond deterioration due to corrosion of internal post-tensioned tendons. The structural behaviour is analysed for different typologies of bridge deck composed of…

A simple model for the calculation of the axial load-carrying capacity of corroded RC columns

2015

In the present paper, a simplified model is used to determine the axial load-carrying capacity of compressed short reinforced concrete columns subjected to corrosion processes. The model considers members with circular and square cross-sections and accounts for—cover spalling, —concrete core confinement induced by transverse steel reinforcement, —buckling of longitudinal reinforcing bars. Strength reduction in concrete cover and core due to cracking induced by rust formation, reduction of steel area in longitudinal bars and transverse stirrups due to general and pitting corrosion and loss of confinement pressure are considered. The load-carrying capacity and load-axial strain curves here ge…

Photocurrent Spectroscopy in Corrosion and Passivity Studies. A Critical Assessment

2016

Photocurrent Spectroscopy (PCS) is currently employed for the characterization of solid-state properties of semiconducting and insulating materials, since the knowledge of their band gap is a prerequisite to any possible application in different fields such as: solar energy conversion (photoelectrochemical and photovoltaic solar cells, photocatalysis) and microelectronics (high-k, high band-gap materials) (1-2). In the last 20-30 years an increasing number of scientists working in the area of corrosion has been attracted by this technique owing to its versatility and ability to scrutinize in situ corrosion layers and passive films having semiconducting or insulating behaviour. In previous w…

Renforcement de la résistance à la corrosion localisée de l’acier inoxydable 304L grâce au traitement de surface par laser impulsionnel

2013

L’acier inoxydable 304L est utilise dans de nombreux domaines. Cependant, il peut, dans certaines conditions, etre sensible a la corrosion par piquration. Dans cette etude, nous nous sommes interesses aux potentialites du traitement de fusion superficielle par laser nanopulse pour l’amelioration de la resistance a la corrosion de cet acier. Ce traitement consiste a focaliser un faisceau laser sur la surface du materiau, provoquant sa fusion quasi instantanee sur quelques microns, immediatement suivie d’un refroidissement ultra-rapide allant jusqu’a 1011 K/s. Les parametres laser impliquent des modifications des proprietes physico-chimiques. Nous avons notamment etudie l’influence du recouvr…

High Temperature Corrosion of Superheater Tubes in Waste Incinerators and Coal-Fired Plants

2004

Photoelectrochemical Characterization of Oxide Layers on 316L Stainless Steel Grown in High temperature Water

2014

La torre del Tempo: il punto di vista del chimico

2013

L’obiettivo del presente lavoro è stato quello di valutare la tipologia di lega metallica, il suo degrado e la tipologia di vernice dell’opera in ferro policroma “La Torre del Tempo” di E. Tadini. A tale scopo sono state effettuate delle misure di Microscopia Ottica, Diffrattometria a raggi X, Spettroscopia micro-Raman e Spettroscopia NMR. The goal of this study was to evaluate the type and the of conservation state of the metal alloy and the type of varnish of samples coming from “La Torre del Tempo” E. Tadini. The samples were characterized by Optical Microscopy, X-ray Diffractometry, micro-Raman Spectroscopy and NMR spectroscopy.

Evidence for characteristic vascular patterns in solid tumours: quantitative studies using corrosion casts

1999

The vascular architecture of four different tumour cell lines (CaX, CaNT, SaS, HEC-1B) transplanted subcutaneously in mice was examined by means of microvascular corrosion casting in order to determine whether there is a characteristic vascular pattern for different tumour types and whether it differs significantly from two normal tissues, muscle and gut. Three-dimensional reconstructed scanning electron microscope images were used for quantitative measurements. Vessel diameters, intervessel and interbranch distances showed large differences between tumour types, whereas the branching angles were similar. In all tumours, the variability of the vessel diameters was significantly higher than …