Inhibition of C-steel corrosion by some thiadiazole derivatives (I-VI) in 1 M H 2 SO 4 was investigated by weight loss, potentiodynamic polarization, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) techniques. The presence of these compounds in the solution decreases the double layer capacitance, increases the charge transfer resistance and increase of linear polarization. Polarization studies were carried out at room temperature, and showed that all the compounds studied are mixed type inhibitors with a slight predominance of cathodic character. The effect of temperature on corrosion inhibition has been studied and the thermodynamic activation and adsorption parameters were calculated and discussed. Electrochemical impedance was used to investigate the mechanism of corrosion inhibition. The adsorption of the compounds on C-steel was found to obey Langmuir's adsorption isotherm. The synergistic effect brought about by combination of the inhibitors and KSCN, KI and KBr was examined and explained. The mechanism of inhibition process was discussed in the light of the chemical structure and quantum-chemical calculations of the investigated inhibitors.

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Abstract:This study was aimed to estimate the prevalence the most common parasites genera infected some freshwater fishes in El-Abbassa, Abu-Hammad, Sharkia Governorate, Egypt with respect to level of water quality in ecosystems. A total of 1828 cultured fish species, represented as 694 Clarias gariepinus, 288 Cyprinus Carpio and 846 Oreochromis niloticus were collected seasonally from October 2015 to September 2017 were macroscopically examined, both externally and internally, for presence of parasites. Microscopic examination then conducted to identify the species. Results indicated that, the total prevalence of parasites among examined fish species representing as the following C. gariepinus˃O. niloticus˃C. Carpio, also can be ordered as the following: summer˃spring˃autumn˃winter. This study investigated that an analysis of fish-parasite fauna is very beneficial as prerequisite for awareness of preemptive and control against parasitic disease. The degrees of interactivity among parasites, as well as parameters of species richness point out that, structures of parasite communities are affected by the water pollutants level.