Journal of

Corrosion and Anticorrosion Protection

Volume III, Issue 4, 2008

Content

Toderiţa NEMEŞ, Cristian DEAC, Valentin PETRESCU, Marius BIBU
Study on the improvement of the anticorrosive resistance of steels through combined galvanic and heat treatment

Abstract: Most components of the installations used in the food processing industry are constantly subjected to the corrosive action of various environments, such as humid heat, salty fog or organic acids. Therefore, in order to reduce the high costs imposed by the realising of the entire equipment of stainless steels, solutions are sought for replacing these with carbon steels or low-alloyed steels. The paper presents some researches aimed at increasing the corrosion resistance of parts made of mild steels and of low alloyed steels, used in the food-processing industry. The parts, made of mild steel OLC45 and of low alloyed steel 41MoCr11, respectively, were initially subjected to coating through galvanisation with a nickel layer with a thickness of 50 µm, after which a thermochemical treatment was applied for the layer’s supplementary enrichment, through diffusion, with two chemical elements: chrome and silicon. For the corrosion tests, the layers obtained by the combined treatment were subjected to the action of various environments characteristic for the food-processing industry: wet heat, salt fog and organic acid solutions for time periods of up to 21 days. The tests showed significant increases of the corrosion resistance of the studied steels, to values that were close to those obtained for stainless steels. The materials used here were tested also from the point of view of their potential toxic effects on humans, but no leakage of metallic ions has been identified from them during their usage, so they can be considered as safe in this context.

Ion DURBACĂ
Mathematical Modeling and Simulation of the Dispersion in Air of Industrial Pollutants

Abstract: The assessment of pollution level (quantities and concentrations) generated by a source of pollution emission can be done by either direct determinations of the emitted pollutants concentrations or by mathematical modeling, considering as entry data the emission sources. Because direct measurements can not be done in every point were we want to find out the level of pollution with a certain noxe, the modeling of atmospheric dispersion is necessary, and gives the possibility to establish the values of emission on an ample contour around the pollution source. The paper presents the phenomenon of modeling the dispersion of pollutant emissions in the atmosphere with professional software of modeling-simulation of pollutants dispersion (version AUSTAL 2000) and of the authorized guide of practice for complying with the EU directives of air quality.

Ernest GRÜNWALD , Horaţiu VERMEŞAN, Caius BULEA, Vasile RUS
Dispersion Capacity of Galvanic Electrolytes with Low Metal Content

Abstract: The paper presents a study regarding the dispersion capacity of a sodium hexametaphosphate based zinc plating electrolyte and that of a cyanides based electrolyte. The concentrations in zinc ions used for the sodium hexametaphosphate electrolyte were 5 and 10 g/l and for the one with cyanides 10 and 15 g/l. Cathodic polarization curves were plotted for the two electrolytes at both concentrations. The slope of the curves was determined at 2 A/dm2, a value that corresponds to practical working conditions. Based on the polarization curves, the dispersion capacity of the electrolytes was determined and the influence of zinc ions concentration on the dispersion capacity. The current efficiency was also determined for the two electrolytes at both concentrations in static and agitation conditions. It can be concluded that the sodium hexametaphosphate based electrolytes have resembling properties with cyanides based electrolytes and can successfully replace them in the electrolytic zinc plating process.

Silvia BURCĂ , George VERMEŞAN, Horaţiu VERMEŞAN
Adsorbtion-Ionic Exchange Used to Remove Pollutants Electroplating Wastewater

Abstract: Studies realised in research laboratories around the world emphasise the necessity of using classical processes (precipitation, coagulation-floculation, etc.), followed by finishing processes (residual heavy metal ions removal by adsorption, ionic exchange, electrodialysis). This papers presents, based on literature data, on overwiev of removal from wastewaters electroplating pollutants using adsorption and ionic exchange with natural and sintetyc materials.

Eva TRÎMBIŢAŞU , Daniela POPOVICI, Octav PÂNTEA, Sonia MIHAI, Stelian NEAGOE
Soils and Vegetation Pollution Monitoring Ploieşti City

Abstract: The paper presents a study regarding the content of heavy metals from soil and vegetation in Ploieşti City. There were selected five places to take samples, areas being known to have an intense traffic in this city. The metal contents ((Pb, Cd, Zn, Cu) were estimated by atomic absorption spectrophotometer method. Experimental results are illustrated and graphically discussed.

Horaţiu VERMEŞAN , Nobumitsu HIRAI
The Use of the Atomic Force Microscopy in the Study of Electrochemical Phenomena

Abstract: This study presents the electrochemical phenomena that occur at oxidation and reduction of lead electrode in the sulfuric acid solution (phenomena appearing at the electrode lead/sulfuric acid interface). In this study it has been used atomic force microscopy (AFM), combined with electrochemical polarization, allowing the study of in-situ reactions that occur during electrochemical corrosion of various metals in aggressive environments. In this study was observed in AFM images the oxidation/reduction reactions of the lead electrode, starting with the passage of Pb2+ ions in solution, followed by the crystallization of lead sulphate and the reduction reaction. The benefits of the AFM microscopy compared to electron microscopy (SEM) are: AFM offers a tri-dimensional profile of the surface, the samples analyzed by AFM do not generally require special treatment, microscopy AFM works in air environment or liquid, AFM can provide a higher resolution.

Mihaela BĂRHĂLESCU , Sabina ZĂGAN
Corrosion Behaviour of Superficial Layers Obtained Through Impulse Electrical Discharges

Abstract: The experimental research was made on superficial layers laid-down through electrical sparking on the steel carbon OL 37 probes, the used electrode being made from a corrosion resistant material (Aluminum and Copper). The corrosion speed was determined through gravimetrical method; the superficial layers subjected to the corrosive agent were analyzed by atomic force microscopy.

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