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In this study, effect of Fumaria officinalis extract, as a natural inhibitor, on the corrosion of carbon steel in hydrochloric acid solution has been studied by using electrochemical polarization and electrochemical impedance spectroscopy methods. The results show that the Fumaria officinalis extract have 94.97% mean efficiency at 2.0 g/L concentrations which shows that this extract is a fairly good inhibitor. Polarization curves indicated that this inhibitor is a mixed (cathodic/ anodic) one. According to the obtained results, inhibition efficiency increases by increasing the inhibitor concentration. Investigation of the effect of temperature on the efficiency of the extract was done by electrochemical polarization method in the range of 35- 65°C which shows that efficiency of the extract decrease by increasing the temperature. Adsorption of inhibitor follows the Langmuir adsorption isotherm in this range of temperature. Thermodynamic adsorption parameters (Kads, ΔGads) of inhibitor were calculated by using the Langmuir adsorption isotherm. The values of ΔGads for all temperatures were close to -16 kJ mol-1, which indicates the electrostatic adsorption (physical adsorption) of the extracts molecules on the surface of the metal. Activation parameters of the corrosion process such as activation energies, Ea, activation enthalpies, ΔH* and activation entropies, ΔS*, were calculated by the obtained corrosion rates at different temperatures. The amount of activation energy of the acid solution with the extract is larger than it without the extract which confirm that the adsorption is physical.

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In the present study, spark plasma sintering (SPS) technique was used to fabricate Ti-Al2O3-HA composite. Powders were sintered at 40 MPa pressure for 5 min at 1200 and 13000C. Microstructural characterisation was carried out using scanning electron microscopy (SEM). Density, hardness, electrochemical impedance and polarization test were performed to evaluate the properties of the samples. The results showed that by increasing the sintering temperature from 1200 to 1300 0C the density of the samples increases and the apparent prosity decreases. Also with increasing temperature the hardness of the samples increased from 528HV to 612HV. The result of electrochemical impedance test showed the polarization resistance of the sample enhanced from 222 Ωcm2 to 996 Ωcm2. Furthermore, according to polarization measurements, the corrosion current density was reduced from 16.35 μA/cm2 to 1.47 μA/cm2. The improvement in the corrosion resistance was attributed to the reduction of prosity and the formation of stronger passive film on the sample surface with increasing sintering temperature.