Journal of

Corrosion and Anticorrosion Protection

Volume V, Issue 3, 2010

Content

Anca COJOCARU^a , Ioana MAIOR^a, Iosif LINGVAY^bCarmen LINGVAY^b, Simona CAPRARESCU^a, Danut-Ionel VAIREANU^a
a University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, 1-7 Polizu St, Bucharest, Romania
^b National Institute for Advanced Researches and Development in Electrical Engineering INIDIE ICPE-CA, 313 Splaiul Unirii, 030138, Bucharest, Romania

CONSIDERATIONS REGARDING THE EFFICIENCY OF ENVIRONMENTALLY FRIENDLY NOVEL TYPE INHIBITORS

Abstract: The results of some investigations concerning the inhibition effect of some plant extract on the corrosion of carbon steel in 0.5M H₂SO₄ solutions are presented in this paper. The studies were made using electrochemical techniques: potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The corrosion characteristics in the absence and in the presence of inhibitor were determined using a VoltaLab 40 Electrochemical Dynamic Laboratory with an EIS module. Nyquist plots for the investigated carbon steel samples in sulphuric acid electrolyte solution were drawn for comparative purposes in the absence and in the presence of plant extract of various concentrations show a capacitive loop, very well defined. The potentiodynamic polarization curves were employed to represent the Tafel lines and to extract the kinetic parameters, namely: the corrosion potential, the corrosion current density and the anodic and cathodic Tafel slopes.

Anca-Constantina PARAU^a , Raluca Ioana ZAMFIR^a
a Politehnica University of Bucharest Romania

COMPARATIVE STUDY ON THE CORROSION RESISTANCE OF Co-Cr ALLOYS AND Ni-Cr IN PRESENCE OF THE BACTERIUM FD-MN44

Abstract: The oral cavity is the environment in which oral fluids and dental metal alloys of various chemical and physical compositions can be found. In an oral environment, materials are subjected to a continuous degradation process, through physical-chemical attacks and also because of mechanical pressure. The stress can be mechanical or bacterial, with permanent action. Alloys change their color shade due to corrosion and can generate physiological phenomena. Manufacturing different dairy products, in most cases, is conditioned by the quantity of the present microflora, which through it's action determines those biochemical processes from which results the characteristic product properties. The research has followed corrosion behavior of Co-Cr and Ni-Cr alloys in artificial saliva environment combined with lactic environment containing FD MN44 bacteria (found in dairy products, such as buttermilk), compared with an artificial saliva environment. We used Co-Cr alloy, known in the dental alloys market, as Vitalium(Co-Cr) and Ni-Cr alloy, known in the dental alloys market, as Vera Soft (Ni-Cr). We recorded the variation of the stationary potential in time and also the variation of pH in time, using a Hanna 221 type pH/mV meter and an electrolytic cell.

Doina FRUMUSELU^a
a CNTEE Transelectrica SA Sos. Stefan cel Mare nr. 1A Bucuresti, Romania 011736

CORROSION CONTROL STRATEGY IN THE ELECTRICAL NETWORK INFRASTRUCTURE

Abstract: Given the impact of effects resulting from the biunivocal relationship infrastructure-environment over military operations to maintain peace or to implement post- conflict programmes, a particular attention has to be paid to the management of corrosion issues, the most common degradation process of metallic and non-metallic materials in the composition of installations of electricity transmission and distribution infrastructure. The paper describes the corrosion prevention and control strategy for electrical network infrastructure taking into account: - the economic significance and the vulnerability of the installations to the impact of natural and anthropic hazards/risks; - the constructive type and the wide range of materials constituting the installations; - the geographic location (closeness to industrial platforms, topoclimate, active surface type, etc.); - the condition monitoring of operational installations by means of IR thermography and strain gauges systems. The maps and data base obtained from application of corrosion prevention and control strategy is useful when elaborating the maintenance, updating and monitoring programmes, determining certain solutions with technical- economic efficiency in degradation prevention and fighting depending on the characteristics of geographic location area.

Florina CONSTANTIN^a,b, Jean-Pierre MILLET^a, Marioara ABRUDEANU^b
a INSA-Lyon, MATEIS, CNRS UMR5510, F-69621 Villeurbanne, France;
^b University of Pitesti, Materials Science and Engineering Laboratory, 1 Targul din Vale, Pitesti, 110040, Romania

ENVIRONMENTAL PROTECTION: A CHALLENGE FOR ANTICORROSION RESEARCH - SUBSTITUTION STUDY OF CrVI

Abstract: Each interface metal-environment involves often a corrosion process. Over the years, many researchers have attempted to find why this phenomenon occurs, what are the mechanisms behind the appearance of rust, which are the most effective methods to prevent it. The role of chromium in this field is well known, whether under metal form (deposits of hard chromium, stainless steel) or under ionic form, especially Cr VI (chromium conversion layers, chromates salts added to various media). So it has contributed to prevent corrosion and to protect different materials under corrosive conditions. But due to its environmental toxicity and its risk for human health, chromates applications have been limited, and even forbidden. So, the research of an alternative solution is a real challenge for anticorrosion science. In recent years, less toxic products have been proposed such as molybdate and tungstate ions, because Mo and W are homologue elements of Cr (column VI of periodic table). The objective of the present work is to compare, by electrochemical techniques, the effectiveness of chromate and molybdate ions as corrosion inhibitors for three materials: aluminium alloy Al-Mg, copper and carbon steel. It appears that the change of environment, molybdates replacing chromates is not a too bad solution in the case of Al-Mg alloy and copper. But the galvanic coupling simulation with carbon steel shows that the protection is not satisfactory.

Stefan BALTA^a,b,c , Lidia BENEA^a,b , Bart Van der BRUGGEN^c
a Dunarea de Jos University of Galati, Faculty of Metallurgy and Materials Sciences
^b Research Centre Interfaces - Tribocorrosion and Electrochemical Systems (CC-ITES), Romania
^c Katholieke Universiteit Leuven, Department of Chemical Engineering, Belgium

PROPERTIES COMPARISON BETWEEN DIFFERENT ZINC PLATING ELECTROLYTE TYPES

Abstract: Driving force membrane processes seem to be most useful for water treatment. Membranes are very effective in removing a wide variety of water contaminants. Therefore, the use of these processes in water purification to replace or to improve conventional treatment has increased. An inherent problem of membranes is fouling, the accumulation of materials (foulants) near, on, or within the membrane that causes a reduction in the amount of product water over time. As a result of fouling, capital and operating costs of membrane systems are higher, making them less attractive. Advances in nanoscale science and engineering suggest that many of the current problems involving water quality could be resolved or greatly ameliorated using nanosorbents, nanocatalysts, bioactive nanoparticles, nanostructured catalytic membranes and nanoparticle enhanced filtration among other products and processes resulting from the development of nanotechnology. A membrane is an interphase between two adjacent phases acting as a selective barrier, regulating the transport of substances between the two compartments. The main advantages of membrane technology as compared with other unit operations in (bio) chemical engineering are related to this unique separation principle, i.e. the transport selectivity of the membrane. Separations with membranes do not require additives, and they can be performed isothermally at low temperatues and - compared to other thermal separation processes - at low energy consumption. Nanofiltration (NF) separate or remove small molecules or ions from a solvent (most often water) by means of pressure - driven filtration through a dense polymeric membrane. Combination of selectivity with a high permeability to water and mechanical strength sufficient to withstand high pressures is achieved by using thin film composite membranes comprising a dense film of 10-200 nm (active layer) supported by a thick asymmetric porous film. In this paper the manufacturing processes of Polyethersulfone membranes (PES) is described. A Polyethersulfone membrane was made with different concentration of polymer in N-Dimethylformamide (DMF) and N-Methyl-pyrrolidone (NMP) solvents. In the same time the effect of TiO₂ nanoparticles addition inside of the membranes is discussed. For both types of membranes, the influence of the polymer concentration and solvent on the membrane properties were studied. After the preparations all membranes were studied for a comparison with cross flow and dead-end equipments to see the flux and permeability of pure water. The results show a big influence of polymer concentration, solvent type and TiO₂ nanoparticles on the membranes properties.

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