Caratterizzazione della resistenza a corrosione di leghe ferrose in liquidi ionici a base imidazolo,

The possibility to use ionic liquids (ILs) in several industrial applications, from galvanic to electronics, to CO2 capture in combustion processes, requires a deeper understanding of the compatibility of the ILs of major interest with metallic materials that currently compose industrial plants. This work proposes the evaluation of the corrosion behavior of a carbon steel (API 5L X52) and a stainless steel (AISI 316) in presence of methyl imidazolium based ILs. The analysis focuses on the dependence of ILs corrosiveness on their chemical formulation, with particular reference to the anion composition and to the chain length of the imidazolium cation

Impianti di ionizzazione Cu-Ag per la di disinfezione delle acque e rischi di corrosione per spostamento

The copper and silver ionization system is one of the water sanitation treatments. Effective ionization occurs if the content of copper ions in solution is 0.2-0.4 mg/L and that of silver ions is 0.02-0.04 mg/L. An excess of copper and silver ions can react with other metal surfaces, triggering a deposition reaction, allowing the formation of deposits of more noble metals, and then promoting a localized corrosion phenomenon due to galvanic coupling. In the present paper, two case histories will be presented: one related to a legionella sanitizing plant system of a hospital; the second related to a system of water purification of a vessel on a boat. In both cases, working conditions are illustrated, corrosion morphology is described, focusing on the presence of copper and silver deposits, and the cause of corrosion is presented, estimating a reliable corrosion rate

Organic Inhibitors to Prevent Chloride-Induced Corrosion in Concrete: Atomistic Simulations of Triethylenetetramine-Based Inhibitor Film

Inhibitors are largely used to prevent chloride-induced corrosion in reinforced concrete structures thanks to both a barrier effect on chloride penetration and a competition with the adsorption of the inhibitor. The interaction mechanisms between passive film on carbon steel, the inhibitor molecule, and chlorides still require deeper understanding. Theoretical studies based on molecular mechanics (MM) and molecular dynamics (MD) methods can be useful to better understand the passive film formation and its interaction with chlorides. In this work, the interaction between a triethylenetetramine (TETA) inhibitor film on γ-FeOOH surface and chlorides is studied using MD methods. After MM optimization in the initial adsorption stage, some chlorides are close to protective TETA film. After MD run at room temperature effectively, chlorides remain close to the protective film. In order to have an effective barrier on chloride attack, the metal oxide must remain wholly covered by the protective film. The TETA film well covers the lepidocrocite surface but cannot kinetically efficiently prevent the chloride-induced corrosion compared to other organic films exposing COO− groups because it does not exert any repulsion to chlorides

Hydrogen charging of carbon and low alloy steel by electrochemical methods

Atomic hydrogen can be the result of different processes like electroplating, chemical and electrochemical pickling treatments, in welding or by cathodic processes in corrosive fluids. Moreover, adsorption of atomic hydrogen can affect materials in contact with high pressure gaseous hydrogen. Once entered the material, atomic hydrogen interacts with the metal structure and may produce a "damage" of various forms, such as Hydrogen Induced Cracking (HIC), delayed fracture, blistering and hydrogen embrittlement. In particular, when H2S is present ("sour service"), metallic materials, such as carbon and low alloy steels, may suffer hydrogen damage and hydrogen embrittlement. Sour service materials must be used in compliance with international accepted standards, used worldwide in oil and gas activities, when fluids are classified as sour. The present study has been carried out in order to set up an electrochemical method to charge with hydrogen two typical pipeline materials, carbon and low alloy steels. The reason of the use of an electrochemical method is to avoid any critical conditions from the point of view of preparation, safety and disposal. Hydrogen content in the specimens was measured by two different methods: hot glycerol bath and Inert Gas Fusion (IGF) analysis. Hydrogen content in the specimens is about 0.6-2 ppm; mechanical performances were assessed by means of J integral tests: a pronounced decrease of fracture toughness was observed for H charged specimens.{GRAPHIACAL ABSTRACT

Effetto dell’intermittenza della corrente di protezione nei sistemi di protezione catodica dell’acciaio

The paper reports the results of a preliminary research study on the effects of protection current intermittence on the cathodic protection conditions of buried or immersed pipelines. It is well known that cathodic protection has chemical and electrochemical beneficial effects on carbon steel, which do not disappear instantly in correspondence to the current interruption. According to this premise, laboratory tests of intermittent cathodic protection in which the current has been interrupted cyclically were carried out on carbon steel specimens in soil-simulating solution. The effects of the duration of the current-off time, the number of on-off cycles, and of the applied current density have been studied. Potential has been monitored weekly and the residual corrosion rate was calculated by means of a simple electrochemical model

TiO2 Microparticles Incorporation in Coatings Produced by Plasma Electrolytic Oxidation (PEO) on Titanium

This research describes the influence of two types of particles, namely rutile and anatase microparticles (average d < 5 μm), on the morphology, structure, and anticorrosive properties of PEO coatings on titanium produced in an alkaline solution based on NaOH and sodium metasilicates. The paper reports the experimental results relating to the study of the influence of the electrical regime and working frequency of the anodizing treatment on the interaction between the particles, the substrate, and the oxide to determine the optimal conditions that favour the incorporation of the particles and the production of a thick oxide. PEO coatings are characterized by using a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, and X-ray diffraction (XRD) testing. The electrochemical behaviour is evaluated by free corrosion potential monitoring and electrochemical impedance spectroscopy analysis (EIS) performed in a sulphuric acid solution. The particles are successfully incorporated into the coating under any electrical condition and at any frequency. However, only treatments carried out at 1000 Hz allow the production of coatings that combine a large thickness (up to 50 μm) and improved anticorrosion behaviour. In contrast, oxide layers produced at 20 Hz and in DC show a quite damaged structure, affecting their anticorrosion behaviour and resulting in lower corrosion potential and impedance values

Utilizzo di nitrati come inibitori di corrosione per le armature nel calcestruzzo

Corrosion inhibitors have been long considered as an effective preventative technique to slow down the onset and/or propagation of corrosion phenomena in reinforced concrete. Several substances have been evaluated as possible candidates, and great interest has been dedicated to nitrite ion. When investigating how these substances slow down corrosion related processes – chlorides diffusion, critical chloride threshold, CO2 penetration and corrosion propagation –interactions between inhibitor and concrete are also vital. Recently, nitrate based compounds have been proposed as corrosion inhibitors, as they present lower cost than nitrites and are already used in concrete as set accelerators. Some studies have shown that nitrates inhibiting mechanism is similar to that of nitrites. This work proposes the evaluation of a nitrate based substance as possible corrosion inhibitor in concrete, and compares its performance with a nitrite based inhibitor