03/05/2021 11:18 صباحا
The toxicity of number of organic and synthetic compounds have led to the use of natural products as anticorrosion agents which are eco-friendly and harmless, In this work, the effect of inhibiting Hibiscus Rosa-sinensis as an inhibitor of green corrosion on the corrosion of pure aluminum alloys 7075 in seawater at four temperatures (303.15, 313.15, 323.15 and 333.15 K) ,Concentrated ( 0,2,4,6,8,mol/L)was studied by electrochemical using method Potentiostat .The results showed that the corrosion rate decreases with increasing the concentration of the inhibitor. The maximum value of the inhibitor efficiency for pure aluminum alloys was (96.96%), at a temperature of 333.15 K and the concentration of the retarder is 4 ml, and the maximum value for the inhibitor efficiency for alloys (7075) was (91.34%) . At a temperature of 303.15 K and the inhibitor concentration of 6 ml, it was observed that the inhibitor follow the Langmuir Adsorption Isotherm interpretation in the mechanism of its action,That is, the materials that inhibit corrosion work according to the adsorption on the surface of the metal and the formation of a single layer,The values of the equilibrium constant resulting from the Langmuir equation were used for the purpose of calculating the standard free energy values of adsorption to determine the quality of adsorption (chemical, physical or joint adsorption). In this study the adsorption involved both chemical adsorption and physics (co-adsorption), but chemical adsorption is the dominant pattern. and that the adsorption process occurs simultaneously on the metal surface because the values of the adsorption energy are negative If the activation enthalpy and the activation entropy are found an infrared spectrum (FTIR) technique was used to determine the active groups in the plant extract before immersion in the corrosive solution and after the immersion process, as there was a difference between the results and the displacement of the FTIR peaks, which is due to the adsorption of the aggregates on the metal surface, it was found Also, the most important groups are phenol compounds, alkaloids and flavonoids.
Weight loss is a second method for measuring the behavior of pure aluminum and its alloys (7075) in the presence of a Hibiscus rosa-sinensis inhibitor with the best concentration where the values indicate a decrease in weight loss with an increase in the immersion time due to surface covering. With a green inhibitor through adsorption, measuring the pH values is the third way to measure the behavior of pure aluminum and its alloys, by measuring the pH values of different periods of immersion to monitor the change in the presence of the green inhibitor. Inhibition of the behavior of pure aluminum indicates an increase in the pH values with increasing immersion time As a result of the increase in alkalinity and the inhibition behavior of the aluminum alloy (7075) to a decrease in the pH value, which may be due to the destruction of the adsorption layer on the surface of the alloy (7075).
The technique (SEM, AFM) was used to study the metal surface before corrosion and after corrosion with the presence and absence of the inhibitory material. The images showed an improvement in the surface properties after adding the active materials and the rate of aluminum dissolution was significantly reduced and a smooth surface appeared by forming a good protective layer from the adsorption of the damper particles on the surface of the metal being responsible for inhibition of corrosion.