Search results for " Corrosion"

Characterization of Thin Passive Film-Electrolyte Junctions.The Amorphous Semiconductor (a-SC) Schottky Barrier Approach

2016

The knowledge of the solid-state properties of passive film is a preliminary task for a full understanding of the electron and ion transfer processes at the metal/oxide and oxide/electrolyte interface. Both processes are of paramount importance in determining the mechanism of film growth and dissolution as well as in determining the nature of the breakdown during the growth of anodic oxide films or the onset of generalized or localized corrosion process (1-2). With very few exceptions, it is a common belief, that most of anodic oxide films, grown on metals and alloys in aqueous solutions, display a semiconducting or insulating behaviour. It is also very well known that in many cases the ini…

UN PROCEDIMENTO PER IL TRATTAMENTO DI ACCIAIO ZINCATO

2019

La zincatura viene comunemente effettuata su acciaio al carbonio per impartigli una protezione attiva, ossia una protezione catodica per anodo sacrificale, oltre che una protezione fisica di tipo barriera. La zincatura potrebbe essere utilizzata anche per barre di armature nel calcestruzzo armato nei casi in cui strutture debbano essere fabbricate in ambienti particolarmente aggressivi, quali atmosfere marine e/o industriali, dove il composito calcestruzzo/metallo può subire carbonatazione e/o attacco da cloruri. Tuttavia, la zincatura ha un effetto collaterale, ossia diminuisce l’aderenza delle barre causando problemi alla struttura. Questa controindicazione ne ha limitato l’uso in questo …

Composite Coatings of Chitosan and Silver Nanoparticles Obtained by Galvanic Deposition for Orthopedic Implants

2022

In this work, composite coatings of chitosan and silver nanoparticles were presented as an antibacterial coating for orthopedic implants. Coatings were deposited on AISI 304L using the galvanic deposition method. In galvanic deposition, the difference of the electrochemical redox potential between two metals (the substrate and a sacrificial anode) has the pivotal role in the process. In the coupling of these two metals a spontaneous redox reaction occurs and thus no external power supply is necessary. Using this process, a uniform deposition on the exposed area and a good adherence of the composite coating on the metallic substrate were achieved. Physical-chemical characterizations were car…

Hydroxyapatite/Chitosan/Collagen coatings through galvanic coupling

In this work, the attention was focused on Hydroxyapatite/ Chitosan/Collagen composite as biocoatings for application in orthopaedic devices. Hydroxyapatite was selected for its osteoconductivity due to its chemical structure similar to bones. Collagen has the same function since 90-95% of bone matrix is constituted of collagen fibers. Furthermore, chitosan are largely used yet in medical field (e.g. antibacterial agent or drug deliver) and in this work were used to create a synergic interaction with hydroxyapatite and collagen to increase the strength and bioactivity of coating. Coatings were fabricated by galvanic deposition process that has different advantages an it does not require ext…

Electrochemical analysis of the first Polish coins using voltammetry of immobilized particles

2017

[EN] A series of 20 denarii from Boleslaus the Brave (992-1025) and Mieszko II Lambert (1025-1034), corresponding to the beginning of the Polish state were studied using the voltammetry of immobilized particles (VIMP) methodology. VIMP experiments, applied to nanosamples of the corrosion layers of the coins in contact with aqueous acetate buffer, provided well-defined responses mainly corresponding to the corrosion products of copper and lead. Such voltammetric responses, combined with X-ray fluorescence (XRF) spectroscopy experiments performed on the same set of coins, and complemented by focusing ion beam-field emission scanning electron microscope (FIB-FESEM) on silver coins from the 19t…

Rôle des espèces sulfures dans la corrosion des aciers non alliés : hétérogénéités de la couche de produits de corrosion et couplages galvaniques

2014

The present study relates to the problem of the long-term interim storage of nuclear wastes. In France, it is envisaged that high-level radioactive wastes will be confined in a glass matrix, stored in a stainless steel canister, itself placed in a carbon steel overpack. The wastes will then be stored at a depth of ~450 m in a deep geological disposal, drilled in a very stiff (indurated) clay (argillite) formation. A temperature as high as 90°C is expected at the steel surface because of the intense radioactivity. Anodic polarization at applied current density was used to synthetize corrosion product layers likely to be formed in storage conditions. The S235 steel electrodes were covered by …

CORROSION RESISTANCE OF DIFFERENT STAINLESS STEEL GRADES IN FOOD AND BEVERAGE INDUSTRY

2020

Consideration of the formation of solids and gases in steady state modelling of crevice corrosion propagation

2007

Abstract One of the challenges in the simulation of crevice corrosion propagation is the rigorous treatment of non-aqueous species (gas or solids), since the appearance of a new phase in a crevice will automatically have an impact on its geometry. This paper presents a simple approach, where heterogeneous reactions are considered in a post-processing step, by determining the conditions of potential, external chemistry (pH, chloride, …) or geometry under which gas or solid phases could appear in the crevice. Thus, as function of these conditions, stability diagrams for the different phases that are liable to appear in an actively propagating crevice can be constructed. Such diagrams (e.g. di…

The use of linear regression methods and Pearson’s correlation matrix to identify mechanical–physical–chemical parameters controlling the micro-elect…

2008

Abstract Machining introduces residual stresses at the specimen surface and modifies the microstructure and the texture in a small volume close to the surface. Such changes are important in controlling the corrosion behaviour of machined workpieces in the presence of an aggressive environment. In the present paper, the relationships between cutting parameters and the surface and subsurface characteristics of machined copper were first quantified experimentally using a complete plan of L 8 (2 3 ) and a linear regression method. The influence of surface characteristics on the local polarisation curves of machined surfaces was then investigated. The shear-type crystallographic orientation gene…

Recent advances in local probe techniques in corrosion research – Analysis of the role of stress on pitting sensitivity

2007

Local probe techniques have been largely applied to predict the spatial distribution of the electrochemical reactions and to quantify the corrosion rate. These local probe techniques are now being developed to capture the temporal information, in-situ and in real-time. Nevertheless only few works have been devoted to investigate with these local probes the role of stress on pitting sensitivity on passive materials. In this paper, a part of the most recent studies based on combination of local electrochemical measurements with finite element mapping of surface stress gradients are reported illustrating the role of inclusions under straining and the mechanical effect of surface preparation on…