Effect of Halide Concentration on the Effectiveness of Banana Peel Waste Inhibitor at 60C

Organic inhibitors have been widely studying to be an alternative corrosion prevention because of its abundance and non-hazardous effect to the environment. One of organic inhibitors which is obtained from plant extract is banana (Musa Paradisica) peel, because it has gallocatechin which is a strong antioxidant. Otherwise, inhibition effectiveness from organic compound decreases during increasing of temperature. However, the addition of other substance like halide ion has provided multiple effect of corrosion inhibitor effectiveness. The addition of the halide ions can enhanced the inhibition efficiency of the organic inhibitors. This research highlights the effect of additional halide concentration to the inhibition effectiveness of Musa Paradisica (banana) peel on API 5 L steel in 3,5% NaCl at temperature 60C. This inhibition performance is investigated using weight loss measurement and electrochemical measurement. Result shows that the maximum inhibition efficiency was observed with the mixture of 500 ppm banana peel waaste extract and 100 ppm potassium iodide at 60C. Also, The blends behaved as mixed type inhibitor. The effectiveness was found to be in order of KI > KBr due to the larger ionic radius in iodide ion. Keywords Banana Peel Waste, Halide Concentration, Organic Inhibitor, Temperature 60C.

I. INTRODUCTION 1 ron and alloys are one of the most consumed metals for constructional and industrial applications [1] especially carbon and low alloy steels which are the most commonly used material for pipeline in oil and gas industry. Corrosion attack can be happened in mild steel which involves the electrochemical reaction and can cause the degradation and damage to the properties of attacked material. Usually, temperature and salt content are high in oil and gas transmission medium ground medium and drilling fluid [2]. One of the methods to prevent corrosion attack is inhibitor, the use of inhibitors is one of the most practical methods for the surface protection against the corrosive media. So, it is great to examine the corrosion inhibitor resistance in high temperature and salt content.
Scientists have focused their research on green corrosion inhibitors from various plant biomass because of their low operating cost and non-hazardous environmental effect [3][4] [5], and [6]. One of plant extract that can be utilized as corrosion inhibitor is banana (Musa Paradisica) peel waste. However, most of banana peel extract was found more efficient in corrosion inhibition of steel than other studied extracts, because gallocatechin is a stronger antioxidant than catechin [7] [8]. But, it is known that the effectiveness of organic inhibitor decreased while the temperature increased [9]. Some types of synergetic chemical matter like halide ion when added to organic inhibitor sometimes can increase the efficiency of corrosion inhibitor in high temperature [10].
The objective of this present study is to investigate the effect of halide ions addition namely potassium iodide and potassium bromide in the effectiveness of inhibition efficiency of banana peel waste (BPW) in concentration of 500 ppm against API 5L grade B corrosion in 3,5% NaCl solution at high temperature especially at temperature 60 0 C. Approximately 36 million tonnes of banana peel is generated every year and this is a potential material for further utilization [11]. Hence, the blends from BPW would be cheap, renewable, non-toxic and abundant.

A. Material Preparation
Test were performed using steel type API 5L Grade B with dimension 2 cm x 2 cm x 0.3 cm for both of weight loss and potentiodynamic polarization measurement. Material was polished with silicon carbide abrasive paper from grade 400-1200 then cleaning using aceton and dried in warm air. For potentiodynamic polarization, material was covered with epoxy resin.

B. Inhibitor Preparation
The fine powder of banana peel was mixed with solvent 70% methanol and 30% distilled water for 72 I hours with ratio between powder and solvent is 1:10. The extraction method using maceration process.

C. Weight Loss Measurement
In weight loss measurement, the prepared material were suspended in 3.5% NaCl test solution at 60 o C for 24 hours with absence and presence inhibitor. Three types of inhibitor that will be used. First only using inhibitor with concentration 500 part per million (ppm). Second, mixture of inhibitor and potassium iodide (KI) with concentration of inhibitor 500 ppm and KI 25 ppm, 50 ppm, 75 ppm and 100 ppm. Third, mixture of inhibitor and potassium bromide (KBr) with concentration of inhibitor 500 ppm and KI 25 ppm, 50 ppm, 75 ppm and 100 ppm. The corrosion rate (mmpy) was calculated using formula (1) : where K is constant, W is different of weight before and after immersion (gr), D is density (gr / cm3), A is surface area of immersion material (mm) and T is time (hour). The inhibition efficiency (IE) of inhibitor was calculated using formula (2) : where CR1 is corrosion rate in the absence of inhibitor and CR2 is corrosion rate in the presence inhibitor [12].

D. Electrochemical Measurement
Electrochemical measurement method is used to know the electrical properties of the inhibitor were conducted with conventional three electrode arrangement. Material specimen with 2x2x0,3 cm steel specimen size were used as working electrode, graphite rod as counter electrode and saturated calomel electrode (SCE) as reference electrode. The experiment was held in solution for 30 minutes to obtain stable state without stirring in temperature 60 0 C.
The Polarization Testing is based on standard (ASTM G5: Potentiostatic and Potentiodynamic Polarization Measurements), and some parameters such as potential (Ecorr), corrosion current density (i corr ), tafel slope and corrosion rate in open circuit potential (OCP) with scan rate 1mV•s -1 using Corrtest Studio 5 version 5.2 software. The inhibition efficiency (IE) were calculated using formula (3) where icorr and i (1) corr is corrosion current density without and with inhibitor, respectively [13].
The EIS test uses standard (ASTM G 59: Polarization Resistance Measurements), using frequency intervals of 10000 to 0.1 Hz with 1mV amplitude observed in Zview Corrtest Software with some parameters such as Resistance solution (Rs), Resistance polarization (Rp), Coefficient double layer (Cdl) By Nyquist plot. With the efficiency using formula (4) and (5) where f is the frequency (Hz), Rp1 is the polarization resistant without the inhibitor and Rp2 is polarization resistant with the inhibitor [13].

A. Wieght Loss Measurement
The corrosion of API 5L grade B steel in 3,5% NaCl solution in the absence and presence of banana peel waste (BPW) as inhibitor and the mixture of halides including Potassium Iodide (KI) and Potassium Bromide (KBr) was studied using weight loss measurement at temperature 60 0 C. Table 1 gives the values of the corrosion rate and the inhibition efficiency as a function of the presence of 500 ppm inhibitor and halide concentration.
From Table 1, it is known that banana peel waste (BPW) can reduces the corrosion rate and the inhibition efficiency of BPW is increased with the increasing concentration of halide. The reason that banana peel can reduces the corrosion rate can be explained as adsorption of organic matters of the extract on metal surfaces which increased the surface coverage area as well as declining corrosion rate [8]. From the Table 1 it is also known that the addition of halide reduces the corrosion rate of API 5L grade B steel at temperature 60 0 C. The maximum inhibition efficiency was found in the addition of 100 ppm halide in Potassium Iodide and Potassium Bromide addition. The results reveal that there is a synergistic effect between inhibitor molecules and halide ions. The addition of KI reduces the corrosion rate larger than the addition of KBr. The order of inhibition efficiency of halide ions were KI > KBr with percentage of inhibition efficiency given by the highest concentration of each halide ions (100 ppm) where KI (73,594 %) followed by KBr (69,645 %). The synergistic effect of each halide concentration in all measurement was found to increase in order Br -< I -, which seems to indicate that the radii of halide ions may influence this effect. The iodide ion has the radius of 1.35 Å is more influence to adsorption than bromide ion which has the radius of 1.14 Å. Because of the larger ionic radius, the iodide ion has higher hydrophobicity as compared to the bromide ion [14]. The adsorption of Iions onto the metal surfaces will decrease the hydrophilicity of the metal surfaces, which is likely to promote the adsorption of organic molecule in replace of the water molecules. Thus, the inhibition efficiency of BPW is enhanced to a considerable extent in the presence of KI.

B. Polarization Measurement
In order to study further about the inhibitor mechanism and the type of inhibitor of BPW at temperature 60 0 C, polarization curve experiment was conducted. Figure 1 shows the potentiodynamic polarization behaviour of API 5L grade B in 3,5% NaCl solution in the absence and presence of banana peel waste (BPW) as inhibitor and the mixture of 100 ppm halides.
The corrosion electrochemical parameters, such as corrosion potential (E), cathodic and anodic Tafel slopes (bc and ba) and corrosion current density (i) obtained by extrapolation of Tafel lines and the inhibition efficiency are shown in the Table 2.
It is clear from the figure that the Ecorr values were shifted positively in the addition of inhibitor and the combination with KBr and KI. The result in the Table shows that icorr decreased when BPW was added with the halide ions. This fact indicating that the addition of halide ions in BPW inhibitor retard corrosion rate of API 5L Grade B sample in 3.5% NaCl solution. If the value (Ecorr = Ecorr uninhibited -Ecorr inhibited) is more than 85mV including anodic or cathodic inhibitor whereas if the value is less than 85mV including mixing inhibitor [15]. As can be seen from the electrochemical parameters, the largest displacement of corrosion potential of API 5L grade B steel shifted less than 85 mV after BPW and halide ion addition. So, this mixture between BPW and halide ion was classified as mixing inhibitor.

C. Electrochemical Impedance Spectroscopy Measurement
The corrosion of API 5L grade B steel in 3,5% NaCl solution in the absence and presence of banana peel waste (BPW) as inhibitor and the mixture of halides including Potassium Iodide (KI) and Potassium Bromide (KBr) was studied using electrochemical impedance spectroscopy measurement at temperature 60 0 C as shown in Figure 2. Table 4 gives the values of some impedance parameters such as Resistance solution (Rs), Resistance polarization (Rp), and Coefficient double layer (Cdl).
The depressed form of semicircles is often referred to as frequency dispersion which has been attributed to surface heterogeneity of structural or interfacial origin such as those found in adsorption processes. The surface heterogeneity usually results from surface roughness, impurities or dislocations, fractalstructures, distribution of activity centers, adsorption of inhibitors, and formation of porous layers [16].
As can be seen in Figure 2 the capacitive reactance arc radius increases gradually after adding the BPW inhibitor, potassium bromide + BPW and potassium iodide + BPW. From Table 3 it is known that the maximum inhibition efficiency occurs in the addition of 100 ppm halide in Potassium Iodide and Potassium Bromide addition where the inhibition efficiency of potassium iodide adding is greater than potassium bromide adding.
The EIS measurement reveals that the mixture of 500 ppm BPW and 100 ppm potassium iodide, the percentage of inhibition efficiency is highest (54,95 %). The result strongly support the observation that the mixture of 500 ppm BPW and 100 ppm potassium iodide could work best as an inhibitor at 60 0 C.

IV. CONCLUSION
From the result of this study, it is concluded that BPW inhibits the corrosion of API 5 L grade B in 3,5% NaCl solution at temperature 60 0 C. Synergistic effect between BPW and halide ions (KI and KBr) have been studied. The maximum concentration of adding halide was 100 ppm. The addition of both halide ions synergistically improve the inhibition efficiency of BPW. The synergism was found to be in order of KI > KBr due to the larger ionic radius in iodide ion. From Tafel Polarization study, it is revealed that the mechanism of blend was mixing inhibitor.