الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The industrial and technology revolution have driven the vast use of metals and metals alloys. In return the corrosion problem is growing year after year due to the increasing dependence on metals and its alloys. Corrosion is a vital industrial problem; it affects our everyday life. Carbon steel is widely used as a cheap alloy in many applications either on the industrial or the domestic scale. Iron is the main ingredient in carbon steel, so it is susceptible to rust. Hence, the urging needsto develop cheap and safe corrosion inhibitors. The strict environmental legislations and increasing ecological awareness among scientists have led to the development of green alternatives to mitigate corrosion. Green organic corrosion inhibitors are being introduced now a day as a safe environmental option; especially in food and drinks industries. Green corrosion inhibitors can be used in many industries such as: power generation, petrochemical industry, pulp and paper, chemical processing, water treatment, desalination units, metal and mining, construction and oil, gas and refinery plants. In our work here we studied four types of green corrosion inhibitors in 3% NaCl solution. Among the studied green inhibitors extract of Date palm seed (Phoenix Dactylifera L), Licorice Roots, RhusCoriaria L (Sumac) and Carboxy methylcellulose (CMC). Date palm seed, Licorice roots and Sumac extracts are freshly prepared in our laboratory while CMC was ready purchased from the local market. The corrosion inhibition efficiency of the four green inhibitors was tested for carbon steel substrates, different concentration of the inhibitors were tested. All extracts were investigated by weight loss method and Tafel Polarization techniques. The results obtained from weight loss and polarization studies are in a good agreement. A significant decrease in the corrosion rate of mild steel in 3% NaCl was observed in the presence of Date palm seed, Licorice Roots, RhusCoriaria L (Sumac) and Carboxymethyl cellulose (CMC) extracts. In general, it was found that the corrosion rate decrease with the increase of the inhibitor concentration. A maximum inhibition efficiency of 93% was achieved when using 2000 ppm data palm seeds extract concentration in the 3% wt. NaCl solution, followed by 90% for 3000 ppm concentration of licorice roots extract. An efficiency of84% was achieved when using 2000-ppm RhusCoriaria (Sumac) extract and the lowest inhibition efficiency of all the inhibitors under investigation (77%) was obtained at 400-ppm concentration of Carboxy methylcellulose (CMC). According to potentiodynamic polarization data there is a decrease in the corrosion current density with the increase in the inhibitors concentration, indicating an increase in the corrosion protection with the use of the inhibitor compared to the blank substrate. It is believed that all the four inhibitors are mixed type inhibitors to some degree. Date palm seed extract showing more cathodic shift compared to the other green inhibitors types under this study. Licorice extract is considered a mixed type inhibitor, while RhusCoriaria L. ii and CMC extract is mainly an anodic inhibitor with a slight effect on the cathodic active sites. To investigate the composition of the green inhibitors under study, we carried out elemental analysis using Inductively Coupled Plasma (ICP) and Energy Dispersive X-Ray Analysis (EDX). We observed that date palm seed extract and licorice roots extract contain a high amount of phosphorous and sulfur, in addition to magnesium, calcium, potassium and many other elements. This confirms that both inhibitors contain inorganic salts while the other two inhibitors; Sumac and CMC contain traces of inorganic elements. On top of that it was confirmed from the EDX analysis carried through this study that all the green inhibitors under study has a dominant oxygen and carbon contents in addition to the other inorganic minerals. So, in general it is believed that date palm seed extract has the highest inorganic salt content of all the green organic inhibitors under study followed by licorice, then Sumac and CMC, and all the four inhibitors are rich in organic contents. The main organic function groups in the four inhibitors were investigated using Fourier Transform Infrared Spectroscopy (FTIR). The disappearance of the function groups from the analyzed solution after corrosion, justifies the hypothesis that an organic protective film has formed on the metal surface to enhance the corrosion protection of the carbon steel. The shift to more negative potential in date palm seed extract was attributed to the higher inorganic salt ingredient in the date palm seeds extract. It was found from the literature that inorganic salts might act as a cathodic inhibitor while organic inhibitors may act as an anodic inhibitor. This may confirm that the shift to more positive potential in the case of the Sumac and CMC is driven by the lack of inorganic salts and the dominant organic ingredients.