Papers by Author: Ilona Felhősi

Abstract: The layer formation of phosphonic acids on mica surface as a model system, from aqueous and ethanol solutions has been investigated. The aggregation behavior (critical micelle concentration, cmc) of molecules in the solution phase has been determined by surface tension measurements in order to select the appropriate concentration for the layer formation experiments. Layer formation of self-assembling molecules of alkyl-phosphonic acids has been followed by atomic force microscopy (AFM). Nucleation, growth and coalescence of densely packed islands of phosphonates from ethanol solution have been recorded on mica surface. The structure of islands depends on the length of alkyl-chains. Self-assembly of phosphonates has been also observed from aqueous solution, as presented by octyl-phosphonic acid (OcPA). The height of OcPA islands is 1.46 􀁲 0.22 nm, which is practically equal with the length of molecule (1.4 nm). This shows that OcPA molecules form monolayer height domains on the mica surface.

Abstract: The objective of our studies was to investigate the layer formation of 1, 5-diphosphonopentane (DPP) on zinc surface from aqueous solution. For surface treatment, water based solutions of 1, 5-diphosphono-pentane was applied with different treatment times. Evidence of the adsorption of the diphosphonic acid on the zinc surface was obtained using the Infrared Reflection Absorption Spectroscopy (IRRAS).

Abstract: The ZrO2 coatings were deposited by sol-gel techniques on copper and steel. The film morphology has been investigated by AFM technique. The performance of ZrO2 films as protective layers was investigated by electrochemical techniques and optical microscopy. Firstly, the electrochemical behaviour of the uncoated copper and steel substrates was investigated by cyclic voltammetry in HCl (1 M) and NaOH (0.4 M) solutions having various pH values. Secondly, the anticorrosion protective effect of sol-gel ZrO2 coatings was evaluated by potentiodynamic measurements in degrading media in which substrates were immersed for 1-90 days. The comparisons of electrochemical parameters allow an explanation of the role of the ZrO2 coatings in the increased resistance of steel and copper against corrosion in moderately aggressive environments..

Abstract: Phosphonate layer formation on passive iron surface has been investigated by electrochemical and atomic force microscopy techniques. It was found that phosphonate groups bond more strongly to oxide surface, while metallic iron surface is disadvantageous for phosphonate layer formation in aqueous solutions. The rate of anodic dissolution is continually decreasing due to the time-dependent formation of protective phosphonate layer. The kinetics of phosphonate layer formation on passive iron is determined by the potential applied for preceding passive film formation. The size and shape of iron oxide grains depends slightly on the potential of passivation. Changes in morphology due to the phosphonate layer formation have been recorded by AFM.

Abstract: The selected dihydroxamic acid derivatives, namely oxalyl-dihydroxamic acid (C2) and pimeloyl-1,5-di-hydroxamic acid (C7) have been synthesized and evaluated as corrosion inhibitors for carbon steel in neutral aqueous solution by potentiodynamic polarization and ac impedance methods. C2 molecule acts as good inhibitor with inhibition efficiency value reached 91%; it is well adsorbed most likely throughout the two hydrophilic groups, and forms a protective film on the metal surface. C7 has moderate inhibition efficiency probably due to the presence of long single hydrocarbon chain in the molecule, negatively affect the adsorption process. Addition of Ni2+ to C7 significantly improve the inhibition efficiency, throughout the formation of a dense compact layer of complexes between Ni2+ and C7.