Novel Corrosion Inhibitors for Carbon Steel Alloy in Acidic Medium of 1 N HCl Synthesized from Graphene Oxide

In this study, two nano-derivatives from nano-Graphene oxide (GO) were synthesized. Regarding to GON and GOS by reaction GO with 2-amino ethanol and 2-marcapto ethanol respectively, the GO, GON, GOS were characterized by FTIR, XRD and FSEM. Evaluation prepared compound to inhibitors corrosion for Carbon steel in acidic media at (1 6 ppm) concentration and different temperature 298, 308, 318, 328 K. The electrochemical technique used Tafel plot to measure the efficiency of inhibitor. It was observed that the corrosion rate and charge transfer of the carbon steel for the inhibitor increase with increase of temperature and decrease with increase of the inhibitor concentration in the same temperature. The GON had inhibition efficiency reached 96.96% for the 6 ppm concentration at 298 K.


Introduction
Nowadays the nanocompounds are used in wide field of applications due to their ability to do them because of a large number of the functional groups in their chemical structures.One of them is graphene oxide (GO).In recent years, GO nanosheets have drawn special interest in various fields such as supercapacitors, batteries, and photocatalysis etc.The intriguing properties of GO arises from its chemical composition, which consists of graphene sheets with several oxygenated functional moieties attached, such as hydroxyl, carbonyl, carboxyl and epoxyl groups.In this respect, the chemical composition and physico-chemical properties of GO are attractive towards the application of corrosion resistant properties [1] [2].The use of inhibitors for the control of corrosion for metals and alloys which are in contact with aggressive environment is an accepted practice.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 [3] [4]; inhibitors are added to the acidic solution during the acidizing process to reduce the aggressive corrosive effects of the acid on tubing and casing materials.Inhibitors are widely used for the protection of metals to corrosion in acidic environments.Inhibitors usually protect the metal by adsorbing on the surface and retarding metal corrosion in aggressive media.Therefore, selecting the appropriate inhibitor for a particular metal is very important.Most of the well-known inhibitors are organic compounds containing nitrogen, and oxygen [5].A considerable number of studies have been published on the inhibition of steel and its alloys in acidic medium [6] [7] [8] [9] [10].

Graphene Oxide (GO)
Graphene oxide was synthesized by Hummers method Graphite flakes (2 g) and NaNO 3 (2 g) were mixed in 50 mL of H 2 SO 4 (98%) in a 1000 mL volumetric flask kept under at ice bath (0˚C -5˚C) with continuous stirring.The mixture was stirred for 2 hrs at this temperature and potassium permanganate (6 g) was added to the suspension very slowly.The rate of addition was carefully controlled to keep the reaction temperature lower than 15˚C.The ice bath was then removed, and the mixture was stirred at 35˚C until it became pasty brownish and kept under stirring for one days.It is then diluted with slow addition of 100 ml water.The reaction temperature was rapidly increased to 98˚C with effervescence, and the color changed to brown color, Further this solution was diluted by adding additional 200 ml of water stirred continuously for purification.The solution is finally treated with 10 ml H 2 O 2 to terminate the reaction by appearance of yellow color, the mixture was washed by rinsing and centrifugation with 10% HCl and then deionized (DI) water several times After filtration and drying under vacuum at room temperature (Scheme (1-1)) [11] [12] [13].
Scheme .Chemical equation of preparation of GO.

2-Amino Ethanol and Graphene Oxide Functionalized (GON)
The functionalize GO, (0.5 g) was placed in a (250 mL) dried beaker with (100 mL) DMF and amino ethanol 6.17 mL, 10 mmole) sonicated for 1 h to form homogeneous solution, then added DCC (2.06 g, 10 mmole), DMAP (1.22 g, 10 mmole) into mixture with stir 24 h at room temperature, after the reaction finish, the product was filter, then black powder was dried [14] the preparation process of (GON) is shown in Scheme (2-2).

Electrochemical Measurements
The electrochemical measurements were performed using a potentiostat/galvanostat (ACM) connected to a computer.A three electrode cell assembly, consisting of a C-steel rod embedded in araldite as the working electrode (WE), and a saturated calomel electrode as the reference electrode (RE), aplatinum sheet as the counter electrode (CE), was used for the electrochemical measurements.The temperature of the electrolyte was maintained at the required temperature using a water bath.Before immersion in the test solutions, the WE was polished with a polishing machine using emery paper from 600 to 1200 grade until a mirror image was obtained.Then, the WE was washed with distilled water thenimmersed in acetone for 1Minute in an ultrasonic cleaner.
The WE electrode was prepared directly before electrochemical measurements then immersed in the test solution at open circuit potential for one hour until a steady state potential was obtained polarization measurements were performed.All experiments were performed in aerated solutions.From the pola-rization data, were calculated like the degree of surface coverage (θ), the percent tage inhibition efficiency (% IE), corrosion rate and charge transfer resistance [15].

X-Ray Diffraction (XDR) of GO, GON and GOS
In Figure 2  The Diffraction patterns of X-ray to prepared organic compound particles size is calculated using (Debye-Scherer) Equation where; D: Particles size, λ: X-ray wave length (nm), β: Half width at half maximum (HWHM), K: is s related hape factor, normally taken as 0.9.θ is x-ray angle.From this equation the particle size of grapheme oxide (GO) (16 nm) but to calculated average particle size to prepared organic compounds GON (35.7 nm), GOS (36.11 nm), Also calculatedparticles size using (Williamson-Hall) (W-H) equation [19] [ ] where £ micro strain of particles, the calculated particles size from graphic between ( ) Sinθ on x-axis, ( )

Field Emission Scanning Electron Microscopy (FESEM)
The FESEM of graphene oxide (GO) very sharp edges and flat surface the dark gray areas consist of several layers of sheets also kinked and wrinkled areas [13], shown in Figure 4              The R ct values of the inhibited are increase as the concentration of the inhibitors increases on the other hand increase in efficiency inhibitors due to productive carbon steel surface to resist polarization, and the anodic reaction the dissolution of Iron in carbon steel alloy to reduce in present inhibitors the signification that increase of Tafel (β a ) [25].Open Journal of Organic Polymer Materials

Effect of Temperature
The study of effect of temperature on the corrosion rate to the organic inhibtors on carbon steel alloylwere immersed in 1 M hydrochloric acid with different concentration (1 -6 ppm) of inhibitor at temperature ranging from 298 K, 308 K, 318 K, and 328 K, the activation energy value was calculated from Arrhenius equation [26] Ea ln CR ln A RT where: CR = corrosion rate (mpy), Ea = activation energy (KJ/mol); A = frequency factor, R= molar gas constant (8.3143J•K −1 •mol −1 ); T = temperature (K).
Figure 17, Figure 18, Figure 19 show good relationship between (ln CR) vs (1/T K −1 ) for without and with inhibitors organic compound in 1M HCl solution, straight lines were obtained with slope of (-Ea/R), the activation energy was calculated from slope of Arrhenius plot. the activation energy as the concentration of inhibitor increase which indicates physical adsorption [27] and it due to be corrosion reaction in which charge transfer has been blocked by the adsorption of inhibitor molecular on the carbon steel surface.The activation energy (Ea) value in the presence of corrosion inhibitors is higher than in absence of inhibitor also Ea increase with increasing concentration in inhibitors.
Enthalpy (∆H) and entropy (∆S) of activation have been calculated from the following equation     The positive value of H * ∆ reflect that the process of desorption of the inhibitors on the surface is an endothermic process (chemical adsorption) and it has been clearly observed that the value of H * ∆ increasing as the concentration inhibitor increase.The entropy of activation in mentioned table clear that these values increased positively in the presence of inhibitor than in its absence.The increase of reveals that an increase in disordering takes place from reactant to the activated complex [28] (Tables 4-6).

Adsorption Isotherm
The adsorption isotherms provide basic information about the interaction between the inhibitor and the Carbon steel surface.In this study fit with Langmuir isotherm and the Langmuir isotherm best model to gives of value of (R 2 ) correlation coefficient equal one or approaching one, through R 2 to found Langmuir    where surface coverage (θ) for various inhibitor concentrations, K ads the adsorptive equilibrium constant, C is the concentration of the inhibitor, the isotherms at different temperatures for different concentration of organic compound in 1M HCl, show date in Tables 7-9 and Figures 23-25.
The equilibrium constant for the adsorption process was related to the standardfree energy of adsorption by the expression [30].Open Journal of Organic Polymer Materials
(a) the X-Ray Diffraction (XRD) of grapheme oxide shows a large Open Journal of Organic Polymer Materials interlayer spacing equal to 8.06 A˚ at the position (2θ = 10.97˚)disappearance of the peak at 26˚ due to completely oxidized after the chemical oxidation and exfoliation [13] (Figure 2(b)), GON shows many peaks appear (2θ = 10.97) at

Figure 17 .
Figure 17.Adsorption isotherm plot for ln (CR) vs 1/T to the GO.

Figure 20 ,
Figure 20, Figure 21, Figure 22 are the plots of (ln CR/T) vs (1/T K −1 ) for carbon steel in with and without inhibitors organic compound in 1N HCl solution.Curves showed straight lines with slope ( H * ∆ /R) and intercept ( S * ∆ /R).

Figure 23 .
Figure 23.Langmuir s adsorption isotherm plots for the adsorption of GO at different conc.In 1N HCl on carbon steel surface.

Figure 24 .
Figure 24.Langmuir s adsorption isotherm plots for the adsorption of GON at different conc.In 1N HCl on carbon steel surface.

Figure 25 .
Figure 25.Langmuir s adsorption isotherm plots for the adsorption of GOS at different conc.In 1N HCl on carbon steel surface.

Table 1 .
Tafel parameters for C-steel 1M HCl in the absence and presence of different concentrations of GO at different Temp.

Table 2 .
Tafel parameters for C-steel 1M HCl in the absence and presence of different concentrations of GON at different Temp.

Table 3 .
Tafel parameters for C-steel 1M HCl in the absence and presence of different concentrations of GOS at different Temp.