Corrosion Inhibition property of Amoxicillin drug for Al-2014 alloy in 1M HCl Solution

: We focus on the corrosion behavior of Al-2014 alloy in the 1M HCl acidic medium. Also, the inhibition property of Amoxicillin on Al-2014 alloy was studied with different concentrations at different temperatures. The micrographs with and without inhibitor are examined with FE-SEM. It reveals that the Amoxicillin-treated surface has prevented corrosion compared to the untreated Al-2014 alloy. The potentiodynamic measurements reveal that Al-2014 alloy with 150ppm of inhibitor solution has the highest tendency to prevent corrosion in 1M HCl solution in all the samples at different temperatures. It is also verified from the adsorption isotherm, the high inhibition rate is due to the value of ′𝐾 𝑎𝑑𝑠 ′ ( 6592.3kJ/mol.(25˚C), 4524.09kJ/mol.(35˚C)) and ΔG 0 (25˚𝐶, 35˚𝐶) ≈ −33.8, −33.9𝑘𝐽/𝑚𝑜𝑙.. From the EIS studies, the inhibition samples show a higher ‘R ct ’ value implies good corrosion resistance. It is also confirmed from the equivalent circuit by Nyquist plots.


Introduction
Aluminum is one of the fascinating metal that can find in aerospace engineering because of its unique features in its physical properties and economic affordability. The usage of a material is not just aerospace but also in automobile, medicine, etc. [1]. It is also the third most abundant element constituting about 8.13 % of the earth's crust. Its alloys are also the most important materials for aerospace engineering because of their vast electrical and mechanical properties, such as lightweight with adequate strength, high conductivity and good corrosion resistance due to the barrier oxide film layer. Aluminum is lightweight; its performance is highly beneficial in transport applications that are related to the aerospace industry [1]. The metal has been widely used as construction materials, heat exchangers, catalysts and power lines. Our aims to investigate the corrosion resistance of Al-2014 alloy of the heat-treated [2]. The technological demand is not just fulfilled by their properties but also makes them retain over time. In this work, we are focusing on one of the alloys of Aluminum, i.e., Al-2014 alloy and its corrosion inhabitation property by heat treatment [3].
The Al-2014 alloy is the second popular and strongest alloy in the 2000 series, but its usage is limited because of its poor corrosion resistance. The Anticipation of metal corrosion is important to increase the life span of equipment; normally, it is an important process in aerospace engineering materials. The electronegative heteroatom (N, P, O and S) containing organic compounds acts as corrosion inhibitors. Therefore, some of the pharmaceutical antibiotic drug molecules belong to this type of family [4]. The recent reports on corrosion study of materials are focusing on inhibition property of antibiotic drug by subjecting them in acidic as well as in the alkaline medium. i.e., Levofloxacin has more electronegative atoms π-bonds, which is the critical factor for a molecule to adhere to the surface of the metals, the inhibition property in alkaline medium on carbon steel and Aluminum as reported [5]. The gravimetrically estimated Amoxicillin (1800 ppm after 8 h immersion) on mild steel in 1 N HCl acts as a mixed inhibitor with an inhibition efficiency of 94.47%. [6,7]. Most recently, Tobramycin acts as an anti-corrosive agent on carbon steel in an acidic medium with inhibition efficiencies of 80 %, 90.5 %, 84.3 % [8 ]; the antibiotic Azithromycin acts as an inhibitor for corrosion of mild steel, copper and Zinc in a 0.5 M H2SO4 [9]. Also, the corrosion behavior of Aluminum is studied from antibacterial drugs [10], Nifedipine drug [11], The surface morphology was also investigated to observe any change in the microstructure of the heat-treated specimens produced after corrosion immersion test in an aggressive 3.5% NaCl medium. These alloys show specific behavior in Retrogression and Re-aging (RRA) heat-treatments [12]. The most important feature of the aluminum alloy is the formation of an oxide layer on the surface which acts as a barrier. This oxide barrier breaks due to aggressive environments and thus, learning the corrosion parameters of any alloy is essential, to realize and estimate the corrosion current and its response with a metal surface [13]. Gece scattered the evaluation article in regards to the preparing of medications utilized as metallic deterioration inhibitors under one in the whole of the clever risky environments [14]. Penicillin subordinates containing β-lactam bundle are typically utilized as antibacterial sellers and appeared for the explanation that the potential open door for usage anticipation by methods for the prudence of their make conveying approach, relative low harmful best to circumstance and reasonable atomic structure [15,16]. Amoxiline is the one antibiotic drug is used in the formation of Schiff base molecules these molecules act as good corrosion inhibitors [17].

Materials and Methods.
The commercially available Al-2014 alloy ingots are selected for the present work and the respective elemental composition is obtained from EDAX spectra. The identified elements are given in table 1. Firstly, Al-2014 was melted by subject the material in a furnace by keeping the temperature slightly just above its melting point. Then molten compound is poured into preheated cast-iron molds. The specimens were abraded with silicon carbide papers of different grades (from 600-1500) and then polished with the help of a polishing wheel and cleaned using acetone and double-distilled water and then dried at room temperature. The Amoxicillin is bought from Sigma-Aldrich Chemical Co., Inc. and its molecular structure is given in Figure 1. A standard 1M HCl solution was prepared in distilled water using Analytical grade salt. The inhibitor (50 ppm to 150 ppm) is prepared by dissolved in double distilled water and added to a standard 1M HCl solution.

Microstructure and Elemental analysis:
The microstructures and corrosion morphology of Al 2014 alloy were investigated by Scanning electron microscopy (FE-SEM). The work specimen's surface is examined after the inhibition and before the inhibition similarly EDAX -measurements are also done in the same instruments after the electrochemical tests were observed by FE-SEM.

Weight loss measurements:
The pre-weighted Al-2014 (2.5 cm × 2 cm × 0.025 cm dimension) are immersed in the prepared electrolyte containing 250 ml of 1.0 M HCl with and without inhibitors at 25˚C and 35˚C for 24 h. Then the samples are pulled back and subjected to a twofold wash with deionized water and (CH3)2CO. later all the samples are dried at room temperature. The weight loss of all the samples is gravimetrically estimated with accuracy (99.8%). The disintegration charge in terms of corrosion rate (CR) is estimated from relation (1) [18] and also, the inhibition efficiency is estimated from the following relation (2) [19].
Where: W=Weight loss (mg), D=Density of the specimen (g/cm 3 ), A=area of the specimen (square Inch), T=Exposure time (hours) Where: 0 and are the normal weight reduction of three equal Al 2014 amalgam examples in the absence and presence of inhibitors, individually for 24 h drenching.

Microstructural Studies and Elemental Analysis:
The conditions of the metal (Al-2014 alloy) surface was examined using the SEM- However, the inhibited surface for 50 ppm concentration has pits and cracks found but it is comparatively low with an untreated surface. In the surface analysis, the local erosion of materials leads to a loss in the absence of inhibitors in the acidic medium. When the inhibitor of 50 ppm pits and erosion is seen but it is lower than previous. If the concentration is increased to 100 ppm it continues to reduce the pits and erosion, when the 150 ppm there is lower in the pits and erosion due to the creation of a protective inhibitor film because of complete adsorption of inhibitor molecules on the metal surface. It is also visible in figure 2d.
Similarly, the surface plots are also indicate the same ( figure 2 (a-d)). The elemental analysis is

Tafel polarization measurement
Tafel polarization plots as shown in

Adsorption Isotherm:
The adsorption isotherm is an important factor to predict the source for the inhibition that is directly contributed to the adsorption molecule into the metal surface. [23,24] The inhibition of molecules that took place due to the adsorption into the metal surface, utilizing physisorption or chemisorptions by the electrostatic attraction of charge between metal and molecule or maybe the co-ordination of electron vice versa. Based on the adsorption isotherm factor ( ) we may predict the type of adsorption that leads to inhibition of molecule. The adsorption isotherm is determined through the following relation (4) [25].
Where: 'C' is the concentration of inhibitor in Mole, 'θ' is the surface coverage of inhibitor.
Where; 'R' is the universal gas constant, 'T' is the temperature of the solution medium.
The obtained results are given in Table-4. The ΔG 0 value is negative it indicates spontaneous inhibition of molecule into the metal surface by utilizing its molecular energy instead of external energy. and it is found to be in the range of 31-34 kJ/mole. The obtained value implicates that the value is allowed for physisorption (< -40 kJ/mole). Hence, the present case is regarded as the physisorption of the molecule due to the transfer of charge from an organic molecule to the metal surface [27].

Electrochemical impedance studies:
Through the cautious assessment of electromagnetic impedance spectroscopy, the obtained values are plotted and showed in figure 5 (a&b). The diameter of a semicircle of impedance curve increases with the concentration of inhibiter, it is found to be maximum for 150 ppm at a temperature 25˚C as well as 35˚C. It is the significance of the inhibition efficiency of Amoxicillin more at 150 ppm. If the impedance of the sample is more will tends to more actively resist the rate of corrosion by the inhibitor by forming the protective layer that will act as a barrier for charge and mass transfer [28]. Similarly, the diameter of the semicircles is more than that the sample has the same concentrations at 25˚C. It also infers, if the temperature is increased to 35˚C the Amoxicillin molecules partially lose the activity to resist   molecule. It is concluded that Amoxiline acts as a better inhibitor on Al-2014 alloy. As the inhibitor has good efficacy and the rate of corrosion also decreases, amoxicillin is a stronger inhibitor than the other in the same derivative of drugs. This inhibitor can be used to avoid corrosion in the oil pipe industry.