Journal of

Corrosion and Anticorrosion Protection

Volume III, Issue 2, 2008

Content

B. TUTUNARU, Adriana PĂTRU SAMIDE , M. PREDA, A. CIUCIU
The galvanic corrosion of couple 316L stainless steel/TIALV, in physiological serum

Abstract: Galvanic corrosion of 316L stainless steel / TiAlV couple was studied by using electrochemical measurements. It was observed that the critic pitting potential is shifted towards negative direction. Polarisation resistance for the 316L stainless steel / TiAlV couple was about 5 times smaller than in the case when 316L stainless steel was coupled with Pt. The corrosion current for 316L / TiAlV couple, estimated from Tafel diagram, was of 1.1 μA/cm². This fact is suggesting that the association of 316L stainless steel with TiAlV should be avoided for bioimplants in the human body.

Bogdan-Ion MOCANU , Eva TRÎMBIŢAŞU, Nicolae NAUM, Octav PÀNTEA
Study regarding the anticorrosive action of the volcanic zeolitic tuff in the waste water treatment plants

Abstract: In this paperwork the action of the volcanic zeolitic tuff, which contents clinoptilolite, on the metallic equipments from the Waste Water Tratement Plants (WWTP) is presented from the corrosion point of view. The volcanic zeolitic tuff could be used in the biological stage of WWTP for the biodegradation capacity improvement of the active sludge. This tuff has property to reduce the organic substances by adsorbtion, to increase the settling capacity of the active sludge in the clarifiers and as well as could have property to decrease the corrosion action on the pipes and the dynamic equipments such as rotors of the pumps or scraper bridges of the secondary clarifiers. The experiments were carried out by weight loss method using the metallic specimens, which were kept a various periods of time in waste water both without and with the addition of zeolitic tuff, simulating the conditions from the biological stage. The results were shown in the graphic way.

Gabriela Elena BADEA , Ioana MAIOR, Anca COJOCARU, Teodora BADEA
Significant differences between anodic behaviour of 18Cr-10Ni stainless steel and nickel in 10–80% HCOOH aqueous solutions

Abstract: Anodic potentiostatic curves on 18Cr-10Ni stainless steel and on nickel in 10, 20, 40, 60 and 80% HCOOH aqueous solutions have been recorded at the room temperature. The stainless steel is in active state in all tested solutions and passes in passive state by anodic polarization, presenting an extended domain of stable passivity (960 mV), which shifts to positive potential values with increasing of the formic acid concentration. The oxidation of the formic acid takes place simultaneously with the oxygen evolution in the transpassive region. After polarization, the surface of the stainless steel maintains the color and metallic smooth. Nickel has catalytic effect for the formic acid oxidation. The anodic polarization curves show anodic waves, extended on all the passive region of nickel, having the peak currents higher than those obtained for stainless steel with two magnitude order, in the same solutions. After polarization, nickel surface presented visible changes as pitting, cracks and lost metallic smooth. On nickel surface take place successive/simultaneous and concurrent reactions, which determine dissolution/passivation of nickel and oxidation of the formic acid.

Viorel BRÂNZOI, Florentina GOLGOVICI , Florina BRÂNZOI
Inhibiting effect of some organic compounds on aluminium corrosion in hydrochloric acid solutions

Abstract: Two organic surfactants (sodium dodecyl sulfate and sodium dodecyl benzene sulfonate) were investigated as corrosion inhibitors for aluminium in aqueous solutions of 0.5M HCl using polarization and electrochemical impedance spectroscopy (EIS) techniques. The influence inhibitor concentrations were studied. At the lower overvoltage value the dissolution process is controlled by activation, while at the higher overvoltage value, the dissolution process is controlled by diffusion. Corrosion rate decreased as inhibitor concentration increased. Under the critical micelle concentration the inhibition of those two surfactants is negligible. At a concentration higher than critical micelle concentration, the inhibiting action of surfactants increases rapidly with the increasing of surfactant concentration up to a limiting value. The inhibition of the dissolution process in the presence of surfactants can be explained by adsorption of them on the active sites of the surface. In our case, we presume that the inhibitors of this type are strong adsorbed on the metal surface, when a protector film is formed on the metal surface and as a result, the reaction between the metal and the corrosive solution would take place only via the diffusion of the anions of the aggressive medium through the fine pores of the protector film, which has been formed. The EIS measurements were performed for the aluminium electrode in 0.5M HCl solutions with and without the two surfactants in different conditions (immersion time and inhibitor concentrations).

Felicia BRATU, Lidia BENEA , Jean-Pierre CELIS
Tribocorrosion behaviour of AISI 304L stainless steel in Ringer solution

Abstract: Medical applications where tribocorrosion has to be considered are orthopaedic and prosthetic implants, hip joints, amalgam restorative materials, and orthodontic brackets-archwire structures. In most cases, the degradation of biocompatible implant materials can lead to failure of medical therapy and cause a tissue inflammation. The dependence of the tribocorrosion of stainless steels AISI 304L sliding against corundum in Ringer solution on applied normal force and sliding velocity, has been investigated using in-situ electrochemical current-potential measurements. Applied normal force and sliding velocity were found to greatly affect current and potential during fretting-corrosion. An increase in normal force and sliding velocity induce an increase in current and a decrease in potential accelerating the depassivation rate of the tested stainless steel. Sliding wear affects the repassivation behaviour of stainless steel by increasing the anodic current in the wear track area.

Ionuţ ZAMBLĂU, Simona VARVARA, Ionel Cătălin POPESCU, Caius BULEA, Liana Mureşan
Composite coatings with improved corrosion resistance obtained by coelectrodeposition of copper with Al₂O₃ nanoparticles

Abstract: The aim of this study is to investigate the electrochemical behavior and the anticorrosive properties of copper-alumina nanocomposite coatings on carbon steel. Electrodeposition was carried out in an acidic copper sulphate bath, on OL37 steel rotating disc electrodes, in the presence of two types of Al₂O₃ nanopowder. By using electrochemical investigation methods such as open circuit potential measurements, hydrodynamic voltammetry (Tafel interpretation of polarization curves) and electrochemical impedance method, the corrosion behavior of the copper - Al₂O₃ nanocomposite coatings obtained with two different types of nanoparticles was examined in Na₂SO₄ 0.2 g/L solution (pH=3). The corrosion parameters determined from the polarisation curves confirmed that the corrosion process on copperalumina composite surface is slower than on pure copper surface. On the other hand, the impedance spectra recorded in the absence and in the presence of Al₂O₃ nanoparticles incorporated in the copper coatings show an increase of polarisation resistance in time, which can be explained by the development of corrosion products on the electrode surface. Using a 3RC equivalent electrical circuit, the process parameters were obtained by non-linear regression calculations with a simplex method. From these parameters it can be seen that the aluminium oxide particles embedded in electroplated copper increase the polarisation resistance and decrease the corrosion rate with 1.32 times as compared with electrodeposited pure copper.

Vasile HOTEA , Elena POP, Gheorghe IEPURE, Irina SMICAL, Jozsef JUHASZ, Aurica POP
Dissolution of zinc as corrosion process

Abstract: This study investigated the possibility of accelerated dissolving of metal zinc in sulphuric acid by introducing copper cathode on which evolving hydrogen is much easier than on zinc. It was found out that the acceleration of zinc dissolving is possible and, at constant surface of copper cathode, depends on the quality of electrical contact between copper electrode and zinc.

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