ADS, ALS, AHDS and ADDBS Surfactants as Corrosion Inhibitors for Carbon Steel in acidic Solution

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1 Reserch Journl of Chemicl Sciences ISSN X. ADS, ALS, AHDS nd ADDBS Surfctnts s osion Inhibitors for Crbon Steel in cidic Solution Abstrct Kumr Hrish 1 nd Sunit 2 1 Mteril Science Lbortory, Deprtment of Chemistry, Ch. Devi Ll University, Sirs, Hryn, INDIA 2 Deprtment of Chemistry, Singhni University, Rjsthn, INDIA Avilble online t: Received 21 st Februry 2012, revised 24 th Mrch 2012, ccepted 28 th Mrch 2012 The role of some surfctnts towrds corrosion control of crbon steel in 1.0 M HCl hs been investigted using weight loss nd glvnosttic polriztion techniques. Surfctnts investigted re Ammonium decyl sulphte (ADS), mmonium lruryl sulphte (ALS), mmonium hexdecyl sulphte (AHDS) nd mmonium dodecyl benzene sulfonte (ADDBS). Results showed tht the inhibition occurs through dsorption of the inhibitor molecules on the metl surfce. The corrosion inhibition efficiency ws found to increse with surfctnt concentrtion nd decresed with incresing temperture which is due to the fct, tht the rte of corrosion of crbon steel is higher thn the rte of dsorption of surfctnt molecules. The inhibiting ction of surfctnts re considerbly enhnced by the ddition of KI, due to the increse of the surfce coverge nd therefore indicte the joint dsorption of surfctnts nd iodide ions. Thermodynmic prmeters for dsorption nd ctivtion processes were lso determined. Glvnosttic polriztion dt indicted tht surfctnts ct s mixed-type inhibitors. Keywords: osion inhibitors, surfctnt, crbon steel, HCl solution. Introduction Crbon steel hs remrkble economic nd ttrctive mterils for engineering pplictions owing to its low cost, esy vilbility nd high mechnicl strength. The interest of the mterils rises from their importnce in recent civiliztion. Inhibition of metl corrosion by orgnic compounds is result of dsorption of orgnic molecules or ions t the metl surfce forming protective lyer. This lyer reduces or prevents corrosion of the metl. The extent of dsorption depends on the nture of the metl, the metl surfce condition, the mode of dsorption, the chemicl structure of the inhibitor, nd the type of corrosion medi 1. To prevent the ttck of cid, it is very importnt to dd corrosion inhibitor to decrese the rte of metl dissolution in cidic solutions 2-6. Thus, mny studies concerning the inhibition of crbon steel corrosion using orgnic substnces re conducted in cidic nd bsic solutions The present study imed to investigte the efficiency of some surfctnts s corrosion inhibitors for crbon steel in cidic medi. An ttempt ws lso mde to clrify the effects of concentrtion nd temperture on the corrosion inhibition efficiency of ll the four investigted surfctnt s corrosion inhibitors for crbon steel. The mesurements of corrosion rte nd percentge corrosion inhibition efficiency of different surfctnt towrds corrosion of crbon steel by weight loss nd electrochemicl polriztion technique were performed in 1.0 M HCl without nd with the presence of surfctnts in the concentrtion rnge (10 to 100 ppm). The nme nd moleculr structures of ll the four surfctnts s corrosion inhibitor for crbon steel in cidic medium re given in scheme no. 1. Mteril nd Methods Crbon steel used for the investigtions ws in the form of sheet (0.25 mm thick) nd hd the following composition (w/w): C = 0.14, Si = 0.03, Mn = 0.32, S =0.05, P = 0.20, Ni = 0.01, Cu = 0.01, Cr = 0.01% nd blnce Fe. All the chemicls used were of AR grde nd the solutions were prepred using triple distilled wter. Duplicte or in some cses triplicte experiments hve been performed to verify the reproducibility nd consistency of the experimentl dt. For weight loss mesurements, crbon steel specimens of cm 2 size were cut from the crbon steel sheet. All the metl specimens were mechniclly polished successively with the help of emery ppers of grdes 100, 200, 300, 400 nd 600 µ nd then thoroughly clened with plenty of triple distilled wter nd then with cetone. The specimens were dried with hot ir blower nd stored in desicctors over silic gel After recording the initil weights of crbon steel specimens on Mettler Toledo, Jpn AB 135-S/FACT, single pn nlyticl blnce, (with precision of 0.01mg), they were immersed in tilted position in 250 ml bekers ech hving 200 ml of cidic solution s corroding medium with or without the inhibitor. Experiments were crried out in n electroniclly controlled ir thermostt mintined t constnt temperture of 30, 40 nd Interntionl Science Congress Assocition 1

2 50 0 C with in n ccurcy of ± C. After exposing the specimens for 24 hours, the specimens were tken out from the beker nd wshed initilly under the running tp wter. CH 3 (CH 2 ) 9 S Loosely dhering corrosion products were removed with the help of rubber cork nd the specimen ws gin wshed thoroughly with triple distilled wter nd dried with hot ir blower nd then weighed gin. osion rte in mils per yer (mpy) nd percentge corrosion inhibition efficiency were clculted using the following equtions osion rte in mils per yer (mpy) nd percentge corrosion inhibition efficiency were clculted by weight loss technique using the following equtions. osion rte (mpy) = 534 W (1) DAT Where W = weight loss (mg), D = density of crbon steel (gm/cm 3 ), A = re of specimen (sq. inch), T = exposure time (hours). () Ammoium Decyl sulphte (ADS) CH 3 (CH 2 ) 11 S (b) Ammonium Lruryl sulphte (ALS) CH 3 (CH 2 ) 15 S (c) Ammonium Hexdecyl sulphte (AHDS) The degree of surfce coverge (θ ) of the investigted surfctnt compounds were clculted from the following eqution: W Inh θ = 1 (2) WFree Where, W nd W re weight losses of metl per unit Free Inh re in bsence nd presence of inhibitor t given time period nd temperture, respectively. Liner polriztion resistnce mesurements were crried out potentiostticlly by scnning through potentil rnge of 14 mv bove nd below the CP vlue in steps of 2 mv. Experiments were crried out in bsence nd presence of inhibitors t their different concentrtions nd t constnt temperture of 30, 40 nd 50 0 C. The resulting current is plotted ginst the potentil nd slope of the line is mesured. i The corrosion current density, is relted to the corrosion rte by the eqution, I osion rte (C.R.) (mpy) =. Eq. Wt. (3) D Where Eqution Wt. = Grm equivlent weight of metl/lloy, D = Density of metl (gm/cm 3 ), i = osion current density (µa/cm 2 ). CH 3 (CH 2 ) 11 S 3 (d) Ammonium Dodecyl benzene sulfonte (ADDBS) Scheme-1 Moleculr formul nd structure of four surfctnts The interction of inhibitor molecules cn be described by introducing of n prmeter, S θ, obtined from the surfce coverge vlues (q) of the nion, ction nd both. Synergism prmeter, S θ, ws clculted using the following eqution. S θ = 1 θ 1 2 (4) ' 1 θ 1 2 where θ1 2 = ( θ1 θ2 ) ( θ1θ 2 ), θ 1, surfce coverge by nion, θ, surfce coverge by ction nd ' 2 θ 1, surfce coverge by 2 both i.e. nion nd the ction. Interntionl Science Congress Assocition 2

3 Results nd Discussion Percentge corrosion inhibition efficiency of ll the four surfctnt t different concentrtions for the corrosion study of crbon steel fter exposure to 1.0 M HCl t 30 0 C hve been tbulted in tble 1. It is observed from the tble 1 tht the weight loss decresed, percentge corrosion inhibition efficiency incresed nd therefore the corrosion inhibition strengthened with increse in inhibitor concentrtion from 10 to 100 ppm. This trend my result from the fct tht dsorption nd surfce coverge increses with the increse in concentrtion of surfctnt molecules. The liner vrition of weight loss with time in uninhibited nd inhibited 1.0 M HCl indictes the bsence of insoluble surfce films during corrosion. It is cler from the tbles 1 tht percentge corrosion inhibition efficiency increses with increse in inhibitor concentrtion. The percentge corrosion inhibition efficiency for different investigted nionic surfctnts s corrosion inhibitor increses in the following order d > c > b >. Tble 2 gives the vlues of percentge corrosion inhibition efficiency for different concentrtions of ll the four surfctnt molecules nd M KI. The ddition of KI improves the percentge corrosion inhibition efficiency of the investigted surfctnts molecules significntly. The synergistic effect between surfctnts molecules nd KI is due to interctions between chemisorbed I - ions nd surfctnts molecules. The stbiliztion of dsorbed orgnic ctions on the surfce, which my be exhibited by electrosttic interctions with I - ions, leds to higher surfce coverge nd greter corrosion inhibition. Tble 3 shows synergism prmeters for different concentrtions of ll the four investigted surfctnt ( to d) with ddition of M KI for the corrosion of crbon steel fter 24 hours of immersion in1.0 M HCl t 30 0 C. It is observed from the tble 3 tht synergism prmeters for ll the four investigted surfctnt increse with increse in concentrtion of surfctnt molecules from 10 to 100 ppm. Among the four investigted surfctnts molecules, order of synergism prmeters is < b < c < d. Tble 4 shows typicl current-potentil polriztion curves of crbon steel in 1.0 M HCl in the bsence nd presence of different concentrtions of surfctnt molecules. Vlues of ssocited electrochemicl prmeters such s current density ( i ), corrosion potentil ( E ), Tfel slopes, nd corrosion inhibition efficiency (per cent) s function of surfctnt d concentrtions in 1.0 M HCl re shown in tble 4. It is evident from tble 4 tht the Tfel constnts did not chnge significntly. It is cler from the Tfel plots tht the surfctnt d ws mixed type becuse it enhnces both the nodic nd cthodic polriztion but the node is more polrized when n externl current ws pplied. Addition of surfctnt compounds incresed both cthodic nd nodic over voltge nd cused minly prllel displcement to the more negtive nd positive respectively. The corrosion current density ( i ) decreses with increse in the concentrtion of surfctnt compounds, which indictes tht the presence of these surfctnt molecule retrds the dissolution of crbon steel in 1.0 M HCl nd the degree of inhibition depends on the concentrtion of surfctnt molecule. The vlues of corrosion potentil ( E ) vlues shifted to less negtive vlues on incresing the concentrtion of surfctnt molecule from 10 to 100 ppm. The effect of temperture on the corrosion behvior of crbon steel ws studied by weight loss methods t different tempertures in the rnge C in the bsence nd presence of different concentrtions of compound (d) in 1.0 M HCl medi nd percentge corrosion inhibition efficiency of compound (d) is shown in tble 5. It is obvious from the tble 5 tht percentge corrosion inhibition efficiency increses with increse in the concentrtion of compound (d) nd decreses with increse of temperture. The clculted vlues of the pprent ctivtion energy, E, ctivtion enthlpies, H nd ctivtion entropies, S re shown in tble 6. These vlues indicte tht the presence of the dditives increses the ctivtion energy, E nd the ctivtion enthlpy H, nd decreses the ctivtion entropy, S for the corrosion process. The ddition of inhibitors modified the vlues of E. This my be ttributed to the dsorption of inhibitors on crbon steel surfce nd this dsorption mke n energy brrier nd this energy brrier of corrosion rection increses with increse in concentrtion of the surfctnt molecule, nd hence percentge corrosion inhibition efficiency increses. This suggested tht the process is ctivtion controlled Since, the ctivtion energy vlue of kj mol -1 (tble 6) for HCl inhibitor systems support the fct tht the surfctnts re physiclly dsorbed on crbon steel surfce. According to these reports, E due to chemicl dsorption (>80 kj mol -1 ) is considerbly lrger thn due to physicl dsorption (< 80 kj mol -1 ) the increse in the ctivtion enthlpy ( H ) in presence of the inhibitors implies tht the ddition of the surfctnts to the cid solution, increses the height of the energy brrier of the corrosion rection to n extent depends on the type nd concentrtion of the surfctnt molecules. Mechnism of corrosion inhibition of ll the four investigted surfctnts molecules cn be explined on the bsis of the moleculr size nd the number of dsorption centers. rgnic surfctnt compound (d) should be the most effective inhibitors, inspite of it hs two ctive dsorption centers. The highest inhibition efficiency of the compound (d) my be due to: i. higher moleculr size nd ii. benzene ring contributes p electrons to the dsorption centers nd hence increses the electron density on the dsorption centers. Compounds < b < c in percentge corrosion inhibition efficiency nd this is grees with their moleculr size. Interntionl Science Congress Assocition 3

4 Tble-1 Percentge corrosion inhibition efficiency t different concentrtions of surfctnt for the corrosion of crbon steel fter exposure to 1.0 M HCl t 30 0 C Conc. of Surfctnt Percentge corrosion inhibition efficiency of Surfctnts (ppm) ( ) ( b ) ( c ) ( d ) Tble-2 Percentge corrosion inhibition efficiency t different concentrtions of the four investigted surfctnts ( to d) with ddition of M KI for the corrosion of crbon steel fter 24 hours of immersion in 1.0 M HCl t 30 0 C Conc. of Surfctnt (ppm) Percentge corrosion inhibition efficiency of Surfctnts ( ) ( b ) ( c ) ( d ) Tble-3 Synergism prmeter ( S θ ) for different concentrtions of investigted surfctnt ( to d) with ddition of M KI for the corrosion of crbon steel fter 24 hours of immersion in1.0 M HCl t 30 0 C Conc. of surfctnt (ppm) Synergism prmeter ( S θ ) ( ) ( b ) ( c ) ( d ) Tble-4 The effect of concentrtions of compound (d) on the free corrosion potentil (E corr ), corrosion current density (i corr ), Tfel slopes ( β nd β c ), Percentge corrosion inhibition efficiency (%ge CIE) nd degree of surfce coverge (q) for the corrosion of crbon steel in 1.0 M HCl t 30 0 C Conc. of -E corr, mv i corr, (µa /cm 2 ) - β c (mv/ dec) β (mv/ dec) q %ge CIE surfctnt (d) (ppm) Blnk Interntionl Science Congress Assocition 4

5 Tble-5 The effect of temperture on the percentge corrosion inhibition efficiency of surfctnt (d) t different concentrtions nd tempertures Conc. of surfctnt (d) (ppm) 30 0 C 40 0 C 50 0 C Tble-6 Activtion prmeters of the corrosion of crbon steel in 1.0M HCl in bsence nd presence of different concentrtions of compound (d) Conc. of surfctnt (d) Conclusion kjmol H E ( ) kjmol S ( ) ( Jmol K ) (ppm) All the four investigted surfctnt molecules ct s corrosion inhibitors for the crbon steel in hydrochloric cid solution. Surfctnt molecules dsorb on crbon steel surfce ccording to the Freundlich dsorption isotherm. The surfctnts molecules increse the vlue of ctivtion energy of corrosion nd consequently decrese the rte of dissolution of crbon steel in HCl solution. Polriztion dt showed tht ll the four investigted surfctnt molecules cts s mixed-type inhibitors. The inhibition efficiencies obtined from polriztion nd weight loss mesurements re in good greement with ech other. Increse of temperture leds to the increse in corrosion rte of crbon steel in HCl solution. Addition of KI to surfctnt molecules shows synergistic effect on corrosion inhibition efficiency of orgnic surfctnt towrds crbon steel. References 1. Mzhr A.A., Bdwy W.A. nd Abou-Romi M.M., Impednce studies of corrosion resistnce of luminium in chloride medi, Surf. Cot. Techol., 29, (1986) 2. Stern M. nd Gery A.I.J., Efficiency of xylenol ornge s corrosion inhibitor for luminium in cidic medium, J. Electrochem. Soc., 104, 56 (1957) 3. Myt A.K. nd Al-Rwshdeh N.A.F., Inhibition of cidic osion of Pure Aluminum by Some rgnic Compounds, os Sci., 46, (2004) 4. Ebenso E.E., kfor P.C. nd Ekpe U.J., Anionic Surfctnts s osion Inhibitors for Crbon Steel in HCl Solution, Anti-os. Methods nd Mterils, 37, 381 (2003) 5. Bereket G., Pinrbsi A. nd gretir C., Benzimidzole-2- tione nd benzoxzole-2-tione derivtives s corrosion inhibitors for luminium in hydrochloric cid, Anti-os. Methods nd Mterils, 51, (2004) 6. Foud A.S., Mouss M.N., Th F.I. nd Elnen A.I., The role of some thiosemicrbzide derivtives in the corrosion inhibition of luminum in hydrochloric-cid, os. Sci., 26, (1986) 7. Zho T. nd Mu G., Influence of some surfctnts in the corrosion inhibition of luminium in hydrochloric cid, os. Sci., 41, (1999) 8. Al-Andis N., Khmis E., Al-Myouf A. nd Aboul-Enein H., The kinetics of steel dissolution in the presence of some thiourcil derivtives, os. Prev. Cont., 42, 13 (1995) 9. Kzrji A., Keertit S., Aride J., Bougrin K. nd Soufioui M., osion inhibition of stinless steel by some orgnic substnce, Bull. Electrochem., 16(3), 97 (2000) 10. guzie E.E., osion Inhibition of luminium in cidic nd lkline medi on Snsevier trifscit extrct, os. Sci., 49, (2007) 11. Kliskic M., Rdosevic J., Gudic S. nd Ktlinik V., Aqueous extrct of Rosmrinus officinlis L. s inhibitor of Al-Mg lloy corrosion in chloride solution, J. Appl. Electrochem., 30, 823 (2000) 12. Yurt A., Uluts S. nd Dl H., Electrochemicl nd theoreticl investigtion on the corrosion of luminium in cidic solution contining some Schiff bses, Appl. Surf. Sci., 253, (2006) Interntionl Science Congress Assocition 5

6 13. Abd S.A., Mksoud E.L. nd Foud A.S., Some pyridine derivtives s corrosion inhibitors for crbon steel in cidic medium, Mter. Chem. Phys., 93, (2005) 14. Abiiol.K. nd fork N.C., Studies on the inhibition of mild steel corrosion by 1-phenyl-3- methylpyrzol-5-one in hydrochloric cid (HCl) solution, os. Sci. & Eng., 3, 21 (2002) 15. Ebenso E.E., Inhibition of luminium (AA3105) corrosion in HCl by cetmide nd thioure, Nig. os. J., 1(1), (1998) 16. Kumr H. nd Sunit, CTMAC, CTMAB nd CPC surfctnts s corrosion inhibitors for crbon steel in HCl solution, Intern. J. of App. Engg. Reserch, 6(18), (2011) 17. Kumr H. nd Sunit, Anionic surfctnts s corrosion inhibitors for crbon steel in HCl solution, J. Chem. & Cheml. Sci., 1(1), (2010) Interntionl Science Congress Assocition 6