Search results for " Corrosion"

Modeling and numerical simulation of the propagation of pitting corrosion of iron in chlorinated medium : contribution to the evaluation of the durab…

2012

This study deals with the understanding of the mechanisms of pitting corrosion susceptible to occur on carbon steel selected for high level nuclear waste containers. Transport/reaction models have been developed in order to simulate, by finite element method, the propagation of a pit on iron in chlorinated medium. For conservative models, pit is activated by imposing a potential on metal. Thanks to different parametric studies (geometry, environment…) simulations have permitted to classify, by severity order, the factors responsible of the increase or the inhibition of the localized corrosion rate. Otherwise, experiments on occluded (called « lead-in-pencil ») electrodes confirm that confin…

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…

The use of local electrochemical probes and surface analysis methods to study the electrochemical behaviour and pitting corrosion of stainless steels

2007

Abstract In this paper, the electrochemical microcell technique is combined with ex situ (SIMS and XPS) and in situ (SVET) techniques to study the electrochemical behaviour and pitting corrosion of inclusion-contaning stainless steels. Dissolution of metallurgical heterogeneities, depassivation and pitting mechanisms are first discussed in 1 M NaClO4, pH 3, and 1 M NaCl, pH 3, by considering the chemical composition and morphology of inclusions. The influence of the chemical composition of passive films on the electrochemical reactions and the microgalvanic coupling processes occurring at the corrosion potential is also investigated on the same specimen microstructure.

Safety assessment in N-M-V interaction of prestressed concrete elements subject to degradation of the reinforcements

2021

The estimation of residual life of viaducts and bridges is urgently topical, due to the age of Italian infrastructure network. Among the causes of reduced life of prestressed concrete structures, the role played by corrosion in prestressed reinforcements is fundamental. In fact, the reduction of the reinforcement cross-section with the formation of the outer layer of iron oxides and hydroxides and the bad filling of the ducts, induces an intermediate behaviour between that of external (unbonded) and internal (bonded) prestressing. For these reasons, the evaluation of degradation and its influence on structural safety cannot be neglected in the assessment of sections of existing structures c…

METODO PER IL TRATTAMENTO SUPERFICIALE DI LEGHE DI MAGNESIO PER APPLICAZIONI BIOMEDICALI

2019

L’invenzione oggetto di questo brevetto riguarda il processo di anodizzazione per la produzione di rivestimenti (coatings) su leghe di Magnesio AZ31. Queste leghe sono potenzialmente utilizzabili per la produzione di dispositivi biomedicali quali protesi e stent che sono soggetti a fenomeni di corrosione all’interno del corpo umano che ne possono compromettere il funzionamento. Il vantaggio di queste leghe sta nel fatto che possiedono ottime proprietà meccaniche (il modulo elastico delle leghe di Magnesio AZ31 risulta essere confrontabile con quello dell’osso umano) e risultano biodegradabili, ovvero svolgono la loro funzione di sostegno meccanico per lo stretto periodo necessario, e quindi…

A Chemical Approach to the Modelling of Band Gap of Passive Films for Corrosion Studies

2015

Photocurrent Spectroscopy (PCS) has gained a large consideration in the last decades as in situ technique for the characterization of semiconductors and photoconducting passive film/electrolyte junctions being able to provide information on the location of characteristic energy levels like: flat band potential (Ufb), internal photoemission threshold (Eth) and band gap value (Eg)

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…

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

2014

Silicate and Hydroxide Concentration Influencing the Properties of Composite Al2O3-TiO2 PEO Coatings on AA7075 Alloy

2021

This work evaluates the effect of sodium meta-silicate pentahydrate (SMS) and potassium hydroxide concentrations on properties of Al2O3-TiO2 coatings produced through plasma electrolytic oxidation in a solution containing 3 g L−1 potassium titanyl oxalate, (PTO), using a unipolar waveform with constant current density. The surface and cross-section characteristics of PEO coatings including morphology, elemental distribution, and phase composition were evaluated using FESEM, EDS, and XRD techniques. Voltage-time response indicated the concentration of SMS and KOH had a significant effect on the duration of each stage of the PEO process. More cracks and pores were formed at the higher concent…

Process parameters and surface treatment effects on the mechanical and corrosion resistance properties of Ti6Al4V components produced by laser powder…

2023

Laser powder bed fusion is one of the additive manufacturing technologies which has developed more rapidly in recent years as it enables the production of very complex geometries. Titanium alloys are among the most popular materials in the aerospace industry thanks to excellent mechanical and corrosion resistance. The corrosion behavior and mechanical properties of samples made of Ti6Al4V and characterized by the geometrical features typical of brackets were investigated taking into account the effects of process parameters on porosity and microstructure. A comparison between the corrosion resistance of samples with complex geometry (3D) and specimens characterized by simple geometry (FLAT)…