Gheorghe Nemtoi

Behaviour of the poly(maleic anhydride-co-vinyl acetate) copolymer in aqueous solutions

The alternate copolymer obtained from maleic anhydride and vinyl acetate, poly(maleic anhydride-co-vinyl acetate) (PMAVA), was studied by viscosimetric and potentiometric methods. In aqueous solutions this copolymer is hydrolyzed to two neighbouring carboxyl groups in a structural unit and behaves as a dibasic polyacid. The viscosimetric behaviour of PMAVA was studied in function of copolymer concentration, neutralization degree, concentration of the NaCl added and three samples of diAerent molecular weights were synthesized. The rather low viscosity of the copolymer aqueous solution increases with decreasing PMAVA concentration which makes evident the polyelectrolyte character of this copolymer. By potentiometric titration the PMAVA solutions were studied both in the absence and in the presence of NaCl. The estimated values of pK01 and pK02 correspond to the first and to the second ionization stage, respectively. The electrostatic free energy of the polyion, Ge, was calculated with reference to the number of the structural units in a macromolecule, in function of the neutralization degree. ” 2001 Elsevier Science Ltd. All rights reserved.

SEM‐EDX and microftir studies on evaluation of protection capacity of some thin phosphate layers

This article presents the SEM‐EDX and microFTIR study and the corrosion behavior of new five types of phosphated coatings obtained by coprecipitation in acid aqueous medium of some metal cations, pursuing the influence of the addition of other cations and a moderator of precipitation, on the uniformity and compactness of the layers and on the morphology of dendritic structure of Zn(II) and Fe(II) phosphates. Microsc. Res. Tech. 2012.

Corrosion of Mild Steel by Urban River Water

The corrosion processes of mild steel immersed in river water were investigated. The reaction of the Bahlui River on common steel used in domestic and industrial installations was studied. The corrosion of mild steel is an extensive topic approached in different media, yet little information about river water as a corrosive has been reported. The experimental determinations were performed for short term immersion of four alloys in the laboratory. By using Tafel extrapolation and electrochemical impedance spectroscopy, the corrosion of the alloys was investigated. Scanning electron microscopy coupled with energy dispersive X-ray analysis and Fourier-transform infrared spectroscopy were employed to characterize the morphology of corrosion products and identify their phases. The corrosive activity of river water leads to the formation of inner compact and outer porous layers. The differences between corrosion products formed in the presence of underground and surface waters are described.

RADIOMETRIC METHOD FOR THE STUDY OF THE STEELS CORROSION

A radiometric method based on the β-rays absorption for the investigation of corrosion reactions of some steels in different experimental conditions was proposed. During the corrosion process it was observed that the intensity of the β-rays which penetrated the iron ions layers in solution decreases, while the concentration of these ions which pass into aggressive medium increases due to the anodic dissolution of the steel sample. A more exact kinetic parameter is proposed herein, namely the global rate constant, to characterize the corrosion process.

A clean method of uranium extraction decontamination

The present work is focused on an electrochemical method of uranium extraction. The basic principle of the method is the electrolytic one. Using platinum electrodes it was generated a potential dependence of the uranium concentration on the redox potential. Knowing the potential, the time dependence of uranium extraction from UO2(NO3)*H2O salt and uranium ore solid suspension was studied with good results. Therefore, this method can be considered as clean and in consequence appropriate for uranium decontamination of some solid and/or liquid media. Moreover, the method can be used in extraction decontamination of sand (ore or spent fuel).