Corrosion inhibition of carbon steel in the presence of different concentrations of aqueous extract from henna leaves in 1M HCl solution has been studied using the weight loss and potentiodynamic polarization techniques. The effect of temperature on the corrosion behavior of carbon steel was studied in the temperature range 293–333K. The inhibition efficiency increases with increasing inhibitor concentration but decreases with increasing temperature. The activation and free energies for the inhibition reactions support the mechanism of physical adsorption. The adsorption of henna extract on C-steel surface is endothermic, spontaneous and consistent with the Langmuir adsorption isotherm. The potentiodynamic polarization measurements indicate that henna extract acts as a mixed inhibitor. Surface and protective film analysis have been carried out using; energy dispersive X-ray (EDX), scanning electron microscopy (SEM), Fourier transforms infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis

Biodiesel is an attractive alternative fuel for diesel engines due to its technical, environmental and strategic advantages. The most widely produced biodiesel is the esters of vegetable oils, animal fats or waste cooking oils.In this study, the feasibility of biodiesel production from microalga Spirulina platensis has been investigated. The physico–chemical characteristics of the produced biodiesel were studied according to the standards methods of analysis (ASTM) and evaluated according to their fuel properties as compared to Egyptian petro-diesel. Blends of microalgae biodiesel and petro-diesel (B2, B5, B10 and B20) were prepared on a volume basis and their physico–chemical characteristics have been also studied. The obtained results showed that; with the increase of biodiesel concentration in the blends; the viscosity, density, total acid number, initial boiling point, calorific value, flash point, cetane number and diesel index increase. While the pour point, cloud point, carbon residue and sulfur, ash and water contents decrease. The observed properties of the blends were within the recommended petro-diesel standard specifications and they are in favor of better engine performance