Experimental Investigation of Inhibition on Mild Steel Corrosion in Two Different Acid Mediums by Synthesized Piperazin Derivatives

Corrosion prevention studies show a predominant trend in the recent era. Especially mild steel material was used in many industrial sectors because it has specific properties like malleability and ductility. Corrosion inhibition action of a novel synthesized N-(1,3-benzothiazol-2-yl)-2-[4-furan-2-carbonyl)piperazin-2-yl]acetamide (1,3BFCPA) compound was performed on MS-mild steel material in 1 N HCl and 1 N H 2 SO 4 medium. Using the mass loss data, the inhibitor efficiency has been evaluated on both the acidic and alkaline mediums. The inhibitor shows a maximum inhibitor efficiency on both acidic mediums, but when comparing 1N sulfuric acid, it shows a better efficiency of 90%. Based on surface coverage analysis ( q ) from mass loss data, adsorption isotherms were interpreted to fit the behavior of the inhibitor over the surface of MS material, which shows a Langmuir adsorption isotherm.


INTRODUCTION
To remove the scale deposited over the metal surface, it has been treated in acid pickling baths.The choice of inhibitors generally depends on the type of acid medium used, concentration, temperature, and nature of the metal chosen [1][2][3] .Organic-based inhibitors are known to be the best at protecting metals and equipment made of metal during transportation and storage [4][5][6][7] .Many researchers investigate corrosion inhibitor studies by using various synthesized organic compounds that contain heteroatoms, oxygen and sulphur atoms in their rings [8][9][10][11] .On a report of consumption productivity on copper and its combination, the benzotriazole compound shows a superior inhibition proficiency 12,13 .Three salts of Morpholine in particular Morpholine carbonate, phosphate, and borate, displayed 90% hindrance productivity, while outstanding salts showed an extremely low rate of 40% restraint proficiency 14,15 .In 1.11N Hydrochloric acid medium at three different temperatures, the synthesized Formazan derivative (FD) product was used as an inhibitor 16 .Using organic-based inhibitors that attribute an interaction with the surface of the metal via adsorption, either physical adsorption or chemical adsorption, which forms a coordinate bond between metal and inhibitors 17 , Therefore, in my investigation, (1,3BFCPA) was used as a corrosion inhibitor in 1N HCl and 1N H 2 SO 4 medium at room temperature at estimated two-hour time intervals.Inhibitor studies were performed using weight loss methods, and results were confirmed by electrochemical studies.Adsorption studies also reveal a better result when using (1,3BFCPA) corrosion inhibitor on mild steel material.

Mass Loss Data
In 1N HCl and 1N H 2 SO 4 at room temperature for two hours in various inhibitor concentrations, MS specimens were immersed.After the completion of two hours, the coupons were removed from the immersed medium, and washed with doubled distilled water and acetone.From the initial weight and final weight difference mass loss data was calculated.Mass loss data such as the rate of corrosion and the efficiency inhibitor was calculated using the formula, Corrosion Rate (CR)=(87.6x Difference in Weight)/(Density x Area x Time) The efficiency of the Inhibitor (Inhibition efficiency),

Inhibition efficiency (IE )%=[(W o -W i )/Wo]x100
Where (W i ) and (W o ) are the initial and final weight loss (in g) of MS in the inhibitor presence and absence respectively

Adsorption parameters
Langmuir adsor ption isotherm was calculated using the parameters of adsorption such as DG ads -free energy of adsorption, DH ads -enthalpy of adsorption and ΔDS ads -adsorption entropy, which is presented in the following equation.
Where C inh is the concentration of the inhibitor used, K ads is the Equilibrium Constant, and (q)-Theta is surface coverage.
Where A is a constant, Q ads is the adsorption of heat or enthalpy of adsorption.K ads -Equilibrium constant was calculated from the intercepts value of (1/K ads ) of the straight line received from the plot of Concentration of inhibitor/Surface coverage (q) Vs Concentration of inhibitor.Adsorption of free energy was calculated using equilibrium constant value (K ads ) to the below DG ads = -RTln (55.5K ads ) From the value, a direct line is obtained from the graph which is plotted between log (q/1-q) Vs 1000/T at many concentrations of inhibitor used.The slope is formed from the instant line which is -DH ads /2.303R.Enthalpy of activation (H ads ) calculated from the slop formed.The entropy of activation (DS ads ) is arrived from the equation.

Mass Loss Data
After the preliminar y process, MS specimens are polished with various ranges of emery sheets and punched with numbers at the top.Numbered plates were immersed in different concentrations of the inhibitor in 1N HCl and 1N H 2 SO 4 medium for two hours at room temperature.From the weight loss data, the difference in weight of the plate before and after dipping it in the test solution was calculated and shown in Table 1.

Medium for two hours
The maximum inhibition efficiency of (1,3BFCPA was 87.07% in 1N HCl and 92.46% in 1N H 2 SO 4 obtained at the optimum concentration (100ppm).With the addition of the inhibitor, a strong protective layer is formed on the surface of the metal.The rate of corrosion and efficiency of the inhibitor (1,3BFCPA) are represented in Figures 1 and 2.

Adsorption isotherm
The mass loss data calculated, which gives information about the interaction of the inhibitor (1,3BFCPA) on the surface of the metal coverage (q) in 1N HCl and 1N H 2 SO 4 for two hours at room temperature, is given in Table 2.A barrier is created for mass and rate change during the adsorption of (1,3BFCPA) on the MS surface.The situation prompted the protecting nature of a steel surface from the movement of serious particles in 1N HCl and 1N H 2 SO 4 arrangement.The level of protection expanded with surface assurance by utilizing the adsorbed particles.From Table 2 the data shows that there is no chemisorption, but there is physisorption between the inhibitor and metal surface in both acidic mediums.Fig. 3 clearly shows the fascination between the surface of the metal and inhibitor molecules.Adsorption of loose power (DG ads ), in 1N HCl and 1N H 2 SO 4 became observed to be -6.056kJmol -1 and -5.031 kJmol -1 .The values suggest physisorption takes place in the inhibitor structures.

CONCLUSION
Synthesized organic inhibitor synthesized N-(1,3-benzothiazol-2-yl)-2-[4-furan-2-carbonyl) piperazin-2-yl]acetamide (1,3BFCPA) shows better efficiency on both the acid medium 1N HCl and 1N H 2 SO 4 .On comparing the acidic medium efficiency of the inhibitor, it shows 92.46% on 1N H 2 SO 4 compared to 1N HCl medium.Based on mass loss data the surface coverage (q) is calculated Langmuir adsorption isotherm is obtained which shows a strong attraction between inhibitor and metal surface on both acidic mediums.