Three organic coatings of commercial grade (zinc rich epoxy-polyamide) were applied to steel substrates and immersed for up to 2160 h in 0 . 5M NaCl at 25uC. These coated plates were assessed by ac impedance in the frequency range 100 kHz to 1 mHz. The coatings were evaluated in salt spray and humidity tests according to ASTM B117 and D-2247. X-ray diffraction and X-ray fluorescence techniques were applied to analyse the coated surface. Electrolytic penetration through the coating changes the dynamic characteristics of the conduction and resistance of the coating film of the protected system over time. Equivalent circuits were used to interpret the physical and electrochemical properties of the changes so, for each coating system, equivalent circuits were appointed using analysis of impedance curves. The numerical quantities of elements were estimated by the Boukamp method. The mechanism and kinetics of the electrochemical systems were assessed by studying the changes in electrochemical parameters v. time. The qualities of the coatings can be compared by measuring the fluctuations in capacitance, dielectric constant and percentage of water uptake. The results obtained from impedance and salt spray tests were compared. Results showed that the best quality coatings can be introduced by measuring the capacitance, water uptake and dielectric constant. SE/S297Mr Neshati (neshatyj@ripi.ir) and Mr Fardi (fardimr@ hotmail.com) are in the Corrosion Department, National
Mixed block copolymers have been used as a template in the synthesis of new mesoporous silica particles, prepared from sol-gel method. The prominent effect of the block copolymers have been used to provide a new template that controls the surface area and porosity of the particles. Tetraethyl orthosilicate as silica source and two block copolymers, poly(propylene oxide)-b-poly(ethylene oxide)-b-poly(propylene oxide) and poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (Pluronics) as a surfactant, were used in water/n-octane co-solvent with citric acid catalyst to prepare new nanostructures of mesoporous silica (SPB 1 and SPB 1,2 ). The displacement of ethanol with cyclohexanol as a co-surfactant drastically changed the surface properties of the new mesoporous silica particles (SPB 1,2 ). The surface area, porosity, morphology, and microstructure of particles were characterized by X-ray diffraction, nitrogen adsorption-desorption, scanning electron microscopy), and transmission electron microscopy. The prepared particles have been specifically characterized for specific use and applications as supporting catalysts for the polymerization of vinyl acetate, drugs delivery, and in the membranes manufacturing based on polyurethanes.
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