Abstract
Synergistic effect of KI on the corrosion inhibition efficiency of 3-acetylpyridine phenylhydrazone (3APPH) on carbon steel (CS) in 0.5 M sulphuric acid solution has been investigated using gravimetric studies, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization studies. Gravimetric corrosion studies revealed that 3APPH showed moderate corrosion inhibition efficiency up to 8 h and beyond this period it showed corrosion accelerating behavior. This antagonistic effect of 3APPH is due to the hydrolysis of the molecule in acidic medium. A very high percentage of inhibition efficiency at 24 h was obtained on the addition of KI due to the synergistic effect of iodide ions. The adsorption of 3APPH and 3APPH + KI on the surfaces of the corroding metal obey Langmuir isotherm as obtained by impedance measurements. Polarization studies revealed that 3APPH act as a mixed type inhibitor. Thermodynamic parameters (<svg style="vertical-align:-3.39064pt;width:76.224998px;" id="M1" height="20.0625" version="1.1" viewBox="0 0 76.224998 20.0625" width="76.224998" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,15.775)"><path id="x1D43E" d="M764 650l-7 -26q-61 -10 -91.5 -22.5t-76.5 -48.5l-235 -184q104 -152 208 -276q31 -37 54.5 -48.5t68.5 -16.5l-7 -28h-156q-138 170 -213 284q-19 29 -33.5 35t-33.5 -7l-29 -173q-15 -75 -5.5 -90.5t74.5 -20.5l-5 -28h-260l7 28q58 5 74 21.5t30 89.5l70 378
q12 68 2 83t-72 22l6 28h257l-7 -28q-62 -7 -76 -21.5t-27 -83.5l-32 -172q29 11 78 46q112 84 217 179q18 16 23.5 25.5t-1 14.5t-26.5 8l-30 4l5 28h249z" /></g> <g transform="matrix(.012,-0,0,-.012,13.25,19.863)"><path id="x61" d="M433 39l-85 -51q-27 0 -47 20q-16 16 -24 44q-5 -3 -24 -16.5t-27 -18.5t-23 -13.5t-25 -12t-19 -3.5q-52 0 -86 36.5t-34 85.5q0 71 81 99q128 43 155 65v17q0 54 -23 83.5t-62 29.5q-28 0 -45 -19t-29 -66q-7 -23 -29 -23q-15 0 -29 13t-14 30t31 40q25 19 68.5 40.5
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t-35 -57.5t-13.5 -89q0 -83 42 -130t96 -47q51 0 96 34z" /></g><g transform="matrix(.012,-0,0,-.012,24.756,19.863)"><path id="x73" d="M319 325l-25 -7q-33 99 -103 99q-29 0 -47 -19.5t-18 -49.5t22 -49.5t62 -36.5q63 -26 95 -57t32 -79q0 -64 -50 -101t-115 -37q-35 0 -67.5 10.5t-46.5 23.5q-5 11 -11 51t-6 67l27 5q14 -53 46.5 -88.5t75.5 -35.5q29 0 50 19.5t21 50.5t-19.5 51.5t-59.5 39.5
q-28 12 -46 22.5t-38.5 27t-30.5 38.5t-10 49q0 54 42.5 92t109.5 38q48 0 88 -18q6 -15 13 -50.5t9 -55.5z" /></g> <g transform="matrix(.017,-0,0,-.017,29.75,15.775)"><path id="x2C" d="M95 130q31 0 61 -30t30 -78q0 -53 -38 -87.5t-93 -51.5l-11 29q77 31 77 85q0 26 -17.5 43t-44.5 24q-4 0 -8.5 6.5t-4.5 17.5q0 18 15 30t34 12z" /></g><g transform="matrix(.017,-0,0,-.017,36.448,15.775)"><path id="x394" d="M600 0h-557v24l268 633l28 8l261 -641v-24zM497 50l-194 489l-196 -489h390z" /></g><g transform="matrix(.017,-0,0,-.017,47.344,15.775)"><path id="x1D43A" d="M713 296l-5 -25q-47 -7 -59 -20t-23 -72l-15 -79q-9 -48 -3 -74q-15 -3 -55 -13t-63 -15t-59.5 -10t-70.5 -5q-149 0 -243 80t-94 220q0 169 127.5 276.5t336.5 107.5q91 0 206 -36l-10 -165l-29 -1q1 85 -47.5 126t-146.5 41q-153 0 -243.5 -97t-90.5 -242
q0 -122 68.5 -198.5t188.5 -76.5q121 0 139 75l20 86q13 58 -1.5 70.5t-99.5 20.5l5 26h267z" /></g> <g transform="matrix(.012,-0,0,-.012,59.663,7.613)"><path id="x30" d="M241 635q53 0 94 -28.5t63.5 -76t33.5 -102.5t11 -116q0 -58 -11 -112.5t-34 -103.5t-63.5 -78.5t-94.5 -29.5t-95 28t-64.5 75t-34.5 102.5t-11 118.5q0 58 11.5 112.5t34.5 103t64.5 78t95.5 29.5zM238 602q-32 0 -55.5 -25t-35.5 -68t-17.5 -91t-5.5 -105
q0 -76 10 -138.5t37 -107.5t69 -45q32 0 55.5 25t35.5 68.5t17.5 91.5t5.5 105t-5.5 105.5t-18 92t-36 68t-56.5 24.5z" /></g> <g transform="matrix(.012,-0,0,-.012,59.663,19.863)"><use xlink:href="#x61"/></g><g transform="matrix(.012,-0,0,-.012,64.886,19.863)"><use xlink:href="#x64"/></g><g transform="matrix(.012,-0,0,-.012,71.169,19.863)"><use xlink:href="#x73"/></g> </svg>) were derived from the adsorption isotherms. Surface morphology of the corroding metal was investigated by SEM analysis.
Highlights
Industrial processes such as pickling and descaling will escalate the corrosion rate of metals enormously and the addition of certain organic compounds which contain π-bonds and heteroatoms like N, O, and S is considered as the most useful method for reducing the corrosion of carbon steel in acidic media [1,2,3]
It is evident from the table that the rate of corrosion in the presence of 3-acetylpyridine phenylhydrazone (3APPH) increased with concentration at 24 h
A marked rise in the inhibition efficiency was noted for carbon steel (CS) specimens in the presence of 3APPH + KI
Summary
Industrial processes such as pickling and descaling will escalate the corrosion rate of metals enormously and the addition of certain organic compounds which contain π-bonds and heteroatoms like N, O, and S is considered as the most useful method for reducing the corrosion of carbon steel in acidic media [1,2,3]. To investigate a detailed corrosion inhibition response of the 3APPH on CS, the gravimetric measurements were performed every 2 hours. The hydrolyzed products were inhibited less on the CS surface when compared to the hydrazone (3APPH), and the same was confirmed by performing the gravimetric corrosion studies of CS in sulphuric acid by taking parent amine and ketone as the inhibitor (Figure 2).
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