1. In the name of Allah, the Beneficent, the Merciful ‏ اقْرَأْ وَرَبُّكَ الْأَكْرَمُ الَّذِي عَلَّمَ بِالْقَلَمِ عَلَّمَ الْإِنْسَانَ مَا لَمْ يَعْلَمْ

2. Inhibition of Aluminum Corrosion in 1.25 M HCl by Pomegranate Aqueous Extract By: Boshra. O. Bashraheiil Jawaher. A. al-ahmary Norah. A. al-zahrani Prof. Sanaa. T. Arab King Abd El-Aziz University, Science Faculty For Girls, Chemistry Department. Chem 491 1432-1433

3. DEDICATION This Research presentation is lovingly dedicated to our respective Prof. Sanaa. T. Arab who has been our constant source of inspiration. She has given us the drive and discipline to tackle any task with enthusiasm and determination. Without her love and support this research would not have been made possible. DEDICATION and ACKNOWLEDGEMENT ACKNOWLEDGEMENT We would like to acknowledge the contributions of the following group and individuals to the development of this research: Our class peer research group for the cooperation and camaraderie. We are also heartily thankful to our Prof., Ms. Sanaa. T. Arab, whose encouragement, guidance and support from the initial to the final level enabled us to develop an understanding of the subject of Inhibition of Aluminum Corrosion. To our truly great parents, friends, relatives and teachers who have made available their support in a number of ways, as well as Dr. Saeedah for her intensive support and alignment during the project period. Lastly, we offer our regards and blessings to all of those who supported us in any respect during the completion of the research project. Jawaher. A. al-ahmari Boshra. O. Bashraheel Norah. A. al-zahrani

4. CONTENTS.. - Summary 1.Introduction 1.1. Corrosion and importance of its study 1.2. Aluminum metal 1.3. Inhibitors and safe inhibitors 1.4. Pomegranate aqueous extract 1.5. Previous studies 1.6. The Aim of Study 2. EXPERIMENTAL 2.1. Materials preparation 2.2. Preparation of pomegranate peel (PPE) Extract (Inhibitor) 2.3. Chemical measurement 2.4 Electrochemical methods 2.5 Scanning Electron Microscopy (SEM) Analysis CONTENTS..

5. 3.Result and discussion 3.1 -At constant temperature (30°C) 3-1-1. Chemical Study 3-1-1-1 Hydrogen evolution 3-1-1-2 Mass loss 3-1-2. Electrochemical study 3-1-2-1.Impedance method (EIS) 3-1-2 -2 Potentiodyanamic polarization method (PDP) 3-1-3 Microstructure study of aluminum surface by SEM 3-2. The effect of temperature 4.Conclusion 5. References CONTENTS..

6. 1. Introduction Corrosion is a surface phenomenon known as the attack of metals or alloys by their environment as air, water or soil in chemical or electrochemical reaction to form more stable compounds. 1-1 Corrosion and importance of its study:

7. 1. Introduction 1- A more corrosive environment due to the increasing pollution of air and water. 2- An increased use of metals within all field of technology. 3- The use for special applications as in the atomic energy field of rare and expensive metals. It is necessary to devote more attention to metallic corrosion nowadays than earlier due to:

8. Aluminum, is a metal with a high electronegative potential (-1.67 V). It is also highly resistant to most acidic and neutral solutions due to the formation of a protective oxide film on its surface. This film is responsible for the corrosion resistant of Al in most environments. But its corrosion takes place in aqueous acidic conditions. The corrosion of aluminum and its alloy in acid solutions have extensively been studied 1. Introduction 1-2 Aluminum metal Dissolution of Al at HCl is suggested to be as follows : The anodic reaction (oxidation reaction): Al → Al +3 + 3e - The cathodic reaction (reduction reaction): 2H + + 2e - → H 2 The overall reaction will be: 2Al + 6 H + → 2Al +3 + 3H 2

9. 1. Introduction Inhibitors are substances that, where corrosion occurs in moist environmental, are added to the corrosion medium to lower the corrosion rate by retarding the anodic and / or the cathodic process. Large numbers of organic compounds were studied to investigate their corrosion inhibition potential. All these studies reveal that organic compounds especially those with N, S and O showed significant inhibition efficiency. But, unfortunately most of these compounds are not only expensive but also toxic to living beings. Because of the toxic nature and high cost of some chemicals in preparing currently in use organic inhibitors it is necessary to develop environmentally acceptable and less expensive inhibitors. Natural products can be considered as a good source for this purpose. The replacement of some expensive chemicals as corrosion inhibitors for metal in acid cleaning process by naturally accruing substances (safe inhibitors) of plant or animal origin exhibit in general high surface activity. 1-3 Inhibitors and safe inhibitors

10. Pomegranate aqueous extract Pomegranate pericarp (peel, rind) : contains almost the following compounds with the structures illustrated in (Fig.1 ) : phenolic punicalagins; gallic acid and other fatty acids; catechin, EGCG; quercetin, rutin, and other flavonols; flavones, flavonones; anthocyanidins : Pomegranate aqueous extract

11. 1. Introduction It covers the studies conducted on 2001, 2003, 2004, 2006, 2007, 2008, 2010 and 2011. 1-4 Previous studies:

12. 1. Introduction In the present work, the effect of pomegranate peel extract as green inhibitor against Aluminum corrosion in 1.25M HCl solution has been studied using chemical measurements by weight mass loss and hydrogen evolution. Also, electrochemical study was carried out by polarization and impedance techniques. 1-5 The aim of this study

13. 2- EXPERIMENTAL 2-1 Materials preparation Aluminum metal used for the study is of the chemical composition: Element Mn Ni Fe Pb Si Zn Cr % 0.009 0.043 0.765 0.014 2.242 1.621 0.009 2-2 Preparation of pomegranate peel (PPE) Extracts (Inhibitor): Pomegranate peel were collected from plant trees in Taif in Saudi Arabia, and left to dry in air for two days,then the aqueous extract of the plant was prepared as follows: 1- Weight after grinding (about 40.97 grams) of pomegranate peel in an electric mixer then dissolved in an appropriate amount of deionized water, and heat until boiling. The mixture then cooled for 24 hours and then filtrated. 2. The filtration is repeated several times to extract the same output, then put on the heater to the concentrate the extract. 3- The extract was collect after concentrated it and placed in a standard flask 250 ml capacity and complete to the mark with deionized water, and therefore this is the stock solution for the study. Figure 2. The Steps of Pomegranate Peel Extract Preparation

14. 2- EXPERIMENTAL At constant temperature (30°C) Part (I) The study can be divided in two parts Three methods of measurements were used in this study there are: 1- Chemical Technique 2- Electrochemical Technique 3- Scanning Electron Microscopy Figure 3: Schematic diagram of the system used in chemical measurements

15. 2- EXPERIMENTAL This is done in two ways, hydrogen evolution method (HEM) and mass loss method (MLM) Chemical measurement 2-3 2-3-1-1 Hydrogen Evolution Measurements From the volume of hydrogen gas evolved per minute, the corrosion rate (R), degree of surface coverage (Ө) and the inhibition efficiency (Inh. HE % )were calculated using equations 1, 2 and 3, respectively: R(ml min -1 cm -1 ) = (V° Ht -V 1 Ht ) \ t (1) Ө = 1- (R \ R°) (2) (3 ) Inh. HE = 1- (R`\ R°`) ×100 Where V 1 Ht is the volume of hydrogen gas at time t for inhibited solution and V 1 Ht is the volume of hydrogen gas evolved at time (t ) for uninhibited solution.

16. 2- EXPERIMENTAL This is done in two ways, hydrogen evolution method (HEM) and mass loss method (MLM) 2-3-1-2 Mass loss Measurements Chemical measurement 2-3 From the weight loss results, the corrosion rates, degree of surface coverage, and, the inhibition efficiency (Inh. %) of the inhibitor, were calculated using equations 4,5 and 6, respectively: ∆ W = w 1 -w 2 R` (g min -1 cm -2 ) = ∆ W \ A t (4) Ө = 1 – R \ R° (5) Inh. ML = (1 – R` \ R°`) × 100 (6) Where W 1 and W 2 are the weight of the sample before and after each experiment respectively, and ∆ W is the loss in the sample weight after the study in HCl solution, (Ө) is the degree of surface coverage of the inhibitor, A is the area of the aluminum sample (in cm 2 ), it is the time of immersion (in minutes) and ∆W is the weight loss of aluminum after time (t).

17. 2- EXPERIMENTAL Part (I) Tools Description Electrochemical methods 2-3 Method highlights Two types of electrochemical measurements has been applied which are: 1- Electrochemical impedance spectroscopy (ElS) measurements. 2- Potentiodyanamic polarization (PDP). The inhibition efficiency is calculated from equations 7 and 8 as follows: Inh.R ct % = (1-R -1 ct \ R -1 cto ) X 100 (7) Inh. p % = (1 - I corr \ I° corr. )×100 (8) Figure 4. Schematic diagram for the electrochemical cell

18. 2- EXPERIMENTAL Part 2 at different temperatures The study can be divided in two parts The effect of temperature on corrosion and corrosion inhibition of aluminum in HCl solutions in absence and in presence of pomegranate extract: The study of corrosion and corrosion inhibition of aluminum in 1.25 M HCl in absence and presence of the studied extract (at 3.2x10-3gm/ml.), using chemical measurements, by hydrogen evolution and mass-loss methods at 30,,40,45 and 50°C, is carried out.

19. 3- Result and discussion Part (I) Table (2) : the corrosion rates (R and R’) and inhibition efficiencies (Inh. HE % and Inh. ML %) for Aluminum in 1.25M of HCl solution. Cx10 3 g\ml hydrogen evolutionmass loss R x10 3 Inh %R x10 6 Inh % 0.020.55 - 13.9 - 0.3212.17 40.77 9.41 32.30 0.810.81 47.39 5.798 58.52 1.67.981 61.16 5.43 61.14 3.28.764 57.61 5.283 61.21 9.69.972 51.47 7.264 48.06 11.211.43 30.12 7.894 43.53

20. 3- Result and discussion Part (I) 1- At constant temperature (30°C) The chemical and electrochemical studies of Aluminum in 1.25 M HCl solutions in absence and presence of different concentrations of the aqueous extract of pomegranate at 30 o C were carried out. 3-1-1 Chemical Study Figure (5): the relation between hydrogen evolution with time of Aluminum in 1.25 M HCl solution in absence and presence of different concentrations of the aqueous extract of pomegranate at 30°C.

21. Part (I) Adsorption Isotherm Table (3) Represents the data derived from the application of Langmuir relationship (Θ −1.C) Vs. C inh. TechniquesSlopeK ads (M-1)-ΔG o ads (kJ mol.-1) HEM1.65254.05-20.26 MLM1.65254.05-20.26 3- Result and discussion

22. Part (I) Figure (6) The relation between inhibition % and concentration (C) of the studied extract from hydrogen evolution and mass loss methods

23. 3- Result and discussion Part (I) Adsorption Isotherm Figure (7) Langmuir isotherm adsorption model Aluminum Corrosion in 1.25 M HCl by Pomegranate Aqueous Extract.

24. Part (I) 1- At constant temperature (30°C) 3-1-2 Electrochemical study Table (3): Electrochemical parameters and inhibition percentages from EIS for Aluminum corrosion in 1.25M HCl solution in absence and presence of the studied pomegranate extract at 30ᵒ C. 3- Result and discussion Symbol Cx10 3 g\ml R sol. (Ω.cm. -2 ) R ct (Ω.cm. 2 ) 1/R ct (Ω.cm. 2 ) -1 Inh.% C dl (μF.cm. - 2 )x10 3 1/C dl (μF.cm. -2 ) -1 Inh.% 1/C dl Free Acid 0.000 0.8922.2430.445-1.261793.02- Acid + extract 0.320 1.1412.5910.38513.441.490671.1415.34 0.736 1.2364.0110.24944.082.249444.6443.93 3.200 2.5173.9410.25343.093.905256.0867.71 8.640 1.3333.8540.25941.792.619381.8251.85

25. Part (I) 1- At constant temperature (30°C) 3-1-2-1 Impedance measurements (EIS) Figure (8): Nyquist diagrams for the corrosion of Aluminum in 1.25 M HCl in absence and presence of different concentrations of the aqueous extract at 30°C 3- Result and discussion

26. Part (I) 1- At constant temperature (30°C) 3-1-2 Electrochemical study Table (4): Electrochemical parameters and inhibition percentages from PDP for Aluminum corrosion in 1.25 M HCl containing different concentrations of aqueous extract of pomegranate plant at 30°C. 3- Result and discussion

27. Part (I) 1- At constant temperature (30°C) 3-1-2 -2. Potentiodyanamic polarization measurements (PDP) Figure (9): Polarization curves of Aluminum corrosion in 1.25 M HCl containing different concentrations of aqueous extract of pomegranate plant at 30°C. 3- Result and discussion

28. Part (I) 2-5 Microstructure Study of aluminum Surface by SEM

29. 3- Result and discussion Part (II) 2- At different temperatures 3-2-1 The effect of temperature Table (5): The variation of inhibition percentage with temperature from two chemical methods ( HEM ) and (MLM )..

30. 3- Result and discussion Part (II) 2- At different temperatures Fig(11) Fig(12) 3-2-1 The effect of temperature Figure (11): Volume of hydrogen/time curves of Aluminum in 1.25M HCl (free acid ) at different temperatures. Figure (12): Volume of hydrogen/time curves of Aluminum in 1.25M HCl in presence of ( 3.2x103 g\ml) of the extract at different temperatures

31. 3- Result and discussion Part (II) 2- At different temperatures 3-2-1 The effect of temperature Figure(13): Variation of inhibition efficiency with temperature for the dissolution rate.

32. 3- Result and discussion Part (II) 2- At different temperatures 3-2-1 The effect of temperature Figure (14): Variation of log (R) vs.1\T for of Aluminum in 1.25 HCl in absence and presence of (3.2x10 3 g\ml) of Pomegranate extract at different temperatures.

33. 3- Result and discussion Part (II) 2- At different temperatures 3-2-1 The effect of temperature Figure (15): Variation of log (R\T) vs.1\T for of Aluminum in 1.25M HCl in absence and presence of ( 3.2x10 3 g\ml) of Pomegranate extract at different temperatures.

34. 3- Result and discussion Part (II) 2- At different temperatures 3-2-1 The effect of temperature Table (6): Activation parameters for Aluminum corrosion in1.25M HCl in absence and presence of ( 3.2x10 3 g\ml) of Pomegranate extract at different temperatures

35. 4- Conclusion: Conclusion: The following results can be drawn from this study: 1-Pomegranate is an effective inhibitor of corrosion of aluminum in 1.5 M of HCl solutions. 2-That increasing the concentration of the pomegranate plant extract leads to decrease the rate of hydrogen gas evolution 3-It can be seen that an S shape adsorption isotherms is found and the inhibitive behavior could be attributed due to the adsorption of pomegranate components on the aluminium surface. 4-Langmuir relationship (Θ −1.C) Vs. C inh where the adsorption parameters are recorded for the studied extracts of pomegranate plant from the chemical study

36. 4- Conclusion: 5-The results applied give linear correlation coefficients close to one which confirms that the adsorption of the extracts components on the surface of aluminum sample, the negative value of ΔG o ads surface is spontaneous, The value of K is relatively large indicating that higher interaction and the extract molecules are physically adsorbed. 6-The impedance curves often give a semi-circle which indicates that the process of corrosion of aluminum under study are mainly controlled by charge transfer 7-The size of the semicircles increased with increase in extract concentrations up to 3.2 x10 -3 gr/ml, At higher concentrations a decrease in the inhibition is found,this is in agreement with the results obtained from the chemical study.

37. 4- Conclusion: 8-Polarization displacement the Tafel lines in both anodic and cathodic directions, this means that the aqueous extract of pomegranate plant reacts as mixed type inhibitors 9-The corrosion rate of aluminum in different temperature increases with rising temperature in both uninhibited (free acid ) and inhibited acid i.e., the slope of the resulting straight lines mostly increases. 10-The variation of the Inh. % with temperature seen that the inhibition percentage almost decreases with the increase of temperature 11-The inhibition of corrosion is decrease indicating that a new compound or a new way of adsorption may through a chemical adsorption is produced. 12-Values of apparent activation energy, ΔE app were calculated from the slopes of the straight lines. The results are in good agreements with that obtained by a number of authors (84.57 kJ mol -1 ).

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