Journal of

Corrosion and Anticorrosion Protection

Volume III, Issue 3, 2008

Content

Silvia BURCĂ , George VERMEŞAN, Caius BULEA, Maria STANCA, Horea BEDELEAN, Andrada MĂICĂNEANU
Electroplating wastewaters pH influence over the ionic exchange capacity of some natural zeolite

Abstract: This work contains some results regarding electroplating wastewaters pH influence over the ionic exchange capacity of a zeolitic volcanic tuff (TVZ) from Pâglişa (Cluj county). We used zeolitic volcanic tuff samples with 0,2-0,4 grain size, washed with distilled water and dried. We worked in static regime, with a solid : liquid ratio of 1:10. We used electroplating wastewater samples (pH 0,5), which were neutralised with NaOH 30%, filtered in order to remove iron oxide precipitate and diluted 100 times. We obtained three wastewater samples of pH 2,3 (labelled A2.3), pH 3,5 (labelled A3.5) and pH 7,3 (labelled A7.3), which were then contacted with the zeolitic volcanic tuff sample. Iron and zinc concentration was determined by molecular absorption spectrometry. We calculated values for ionic exchange efficiency, ionic exchange capacities for the zeolitic volcanic tuff sample and overall (neutralising, filtering and ionic exchange) efficiency. Maximum values for the overall efficiency were obtained for the A7.3 wastewater sample, (95.13% for zinc and 99.79% for iron).

Andreea HEGYI, Horaţiu VERMEŞAN
The corrosion of reinforced concrete structures

Abstract: The corrosion of reinforced concrete structures is a domain that has been studied for a long time with real but unconvincing results due to the complex phenomenology caused by the interaction between the concrete, the reinforcement material and the environment. The main corrosive effects are the concrete carbonization, the chloride ions and the sulfatic attacks. The current researches in the field focus on the theoretical aspects of these phenomena in order to improve the anticorrosive properties of the materials, to find solutions to maintain and rehabilitate the existent structures and to protect the environment.

Lidia BENEA
Electrochemical and structural aspects in co-deposition of dispersed nano-sized SiC with nickel

Abstract: Nano-sized silicon carbide dispersed phase (20 nm mean diameter) were co-deposited with nickel from a Watts electrolyte. The work was focused on two directions: i) Influence of nano and microsized ceramic particles on nickel electrodeposition. The effects were observed by potentiodynamic diagrams and electrochemical impedance spectroscopy measurements performed with and without dispersed particles in the electrolyte. The addition of ceramic particles displaces the nickel reduction curves to more positive potentials. The shift in reduction potential were attributed to an increase in the active surface area due to the adsorbed particles on the cathode and to a possible increase in ionic transport by dispersed particles with their ionic layers adsorbed. It is supposed that the dispersed particles are surrounded by a thin layer of Ni²⁺ and H₃O⁺ ions adsorbed after the particles were introduced in the electrolyte. The charge transfer resistance for ceramic dispersed phase co-deposition with nickel is smaller that than for pure nicke electrodeposition at same plating parameters. ii) Structural aspects of nano and micro composite coatings. The EDX analysis shows the presence of nano and micro ceramic particles in the composite layer. The SEM and TEM investigations show that the composite coatings with nanosized dispersed particles develop in a nodular disturbed surface structure. We suppose that the higher density of nucleation sites due to nanosized silicon carbide particles perturb the growth of nickel matrix resulting in smaller grain size and random orientation of nano composite coating.

Elena POP , Vasile HOTEA, Aurica POP, Romulus POP
The use of the geosynthetic materials for the antierosional protection of the tailing dumps (part i)

Abstract: The tailings generated by the mining and metallurgical industry cover wide surfaces of agricultural and forestry lands destroying the vegetation in the area and giving to the land a distressing aspect. The lack of vegetation and soil substrate determines the occurrence of erosion phenomena that transform the tailings and destroy the cluster of newly installed vegetation. The geocellular carpets provide a simple and efficient solution of making vegetal carpets on the abrupt slopes, carpets with high resilience to the hydraulic erosion.

Ion DURBACĂ
The eco-management and audit scheme (EMAS) – the european standard for the environmental performance of the organizations

Abstract: The Eco-management and Audit (EMAS) is a management tool for companies and other organizations to evaluate and improve their environmental performance. Participation is voluntary and extends to public or private organizations operating in the European Union which ensures a legal and institutional framework for implementing this system as part of the environmental Community acquis.

Ioana MAIOR , Gabriela Elena BADEA, Anca COJOCARU, D.I. VĂIREANU
The corrosion of zinc in zinc chloride solutions and the inhibition effect of urea and thiourea

Abstract: The corrosion of zinc in ZnCl₂ 5% solution, in absence and in presence of 10^-2 and 10^-1 M CO(NH₂)₂, and CS(NH₂)₂ respective, was studied by polarization curves plotted in potentiostatic technique, at a temperature range of 25–55°C. Based on the experimental results were estimated: the Tafel parameters of the corrosion partial reactions, the corrosion potential and current for zinc, the activation energy for the corrosion process and the protection efficiency for the investigated inhibitors. Urea and thiourea act as cathodic inhibitors and present high protection efficiencies at room temperature, which decrease in accordance with temperature increase.

Silvia BURCĂ , George VERMEŞAN , Horaţiu VERMEŞAN
Chemical, physical chemical and electrochemical process used to remove pollutants electroplating wastewaters

Abstract: Used solutions and washing waters resulted during the electrochemical plating, as well as acid or alkaline pickling solutions contain heavy metal ions, zinc, iron, and also alloying metals, with concentrations between 50 mg/dm³ and 100 g/dm³. In our country, zinc electroplating wastewaters treatment is realized mainly, using chemical processes, heavy metal ions precipitation being the most frequent method. After precipitation an important quantity of slurry results, which will raise storage problems. Also, heavy metal ions concentration in wastewaters exceeds many times the maximum allowable concentration imposed by local legislation. Many 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).

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