Helena Otmačić

Copper corrosion inhibitors in near neutral media

The efficiency of nontoxic imidazole derivatives as copper corrosion inhibitors in sodium chloride solutions was studied by electrochemical polarization methods (Tafel extrapolation and polarization resistance method) and weight-loss measurements. Results obtained during this study show that inhibitors with higher molecular weight, especially those with a phenyl ring, have better inhibiting properties. The values of free energy of adsorption, as calculated from Freundlich isotherm, indicate that investigated imidazole derivatives physisorbe on the copper surface.

Energy recovery by pinch technology

This paper shows how the application of pinch technology can lead towards great energy savings. The heat exchanger network of a nitric acid plant has been studied and it was found that it is possible to reduce requirements for cooling water and medium pressure steam. In order to enable these savings, three heat exchangers should be replaced with new ones. Energy consumption in steam power system increases slightly. However, the final result is a reduction of energy costs and a payback time of 14.5 months.

Corrosion Protection of Bronze Patina by New Non-Toxic Organic Inhibitors

From antiquity bronzes have been widely used to produce sculptures and others objects of art. Bronze objects are generally covered with a patina. The patina formed in a long term exposition acquired often a certain protective effect of the substrate metal, but a recent increase of air pollution and/or acid rain damage the bronze exposed in urban environment. A method that reinforces a protective effectiveness of patina becomes therefore necessary. In order to preserve metal works from the aggressive atmosphere, organic inhibitors are often required. The inhibiting effects of two non-toxic organic inhibitors: 1- phenyl-4-methylimidazole and p-tolyl-4-methylimidazole on the patina were examined by the potentiodynamic methods and the electrochemical impedance spectroscopy as well as spectroscopic methods. The morphology and crystallographic structure of artificially obtained patina without and with inhibitor layer were examined with Scanning Electron Microscopy (SEM) and X-ray Elemental Energy Dispersion Spectroscopy (EDS) analyses. The results of these investigations have shown that both inhibitors protect patina in aggressive media.