Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and                    Applications (IJERA) I...
Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and                    Applications (IJERA) I...
Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and                   Applications (IJERA) IS...
Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and                    Applications (IJERA) I...
Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and                    Applications (IJERA) I...
Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and                    Applications (IJERA) I...
Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and                      Applications (IJERA)...
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  1. 1. Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1455-1461 Characterization Studies Of Aqueous Immersion Solutions Of Novel Environmentally Friendly Organometallic Corrosion Inhibitors Used To Cure Mild Steel Substrates In Corrosive Media Volkan Cicek*, Mehmet Ozdemir** *(Faculty of Science and Engineering, Ishik University, Erbil, Iraq) ** (Faculty of Education, Ishik University, Erbil, Iraq)ABSTRACT In this investigation, aqueous immersion carcinogenic and generally regarded as a verysolutions of novel environmentally friendly hazardous soil and groundwater pollutant [1-6].corrosion inhibitors that are used to inhibit Dermatitis and skin cancer have been reported amongcorrosion of mild steel substrate surfaces in workers merely handling components protected by acorrosive media are characterized since chromate film [7]. Many reviews in the literatureimmersion solutions are indicators of the extent of point out to toxicity of chromates associating Cr 6+corrosion, which can even be observed visually in with lung cancer. Although there is no generala qualitative manner, e.g. salt solutions of agreement on the details for the Cr 6+ induced damagegluconate salts remained clear throughout the to DNA resulting in cancers, it is clear that Cr 6+ isimmersion of mild steel coupons, while the salt highly water soluble and it passes through cellsolution in which the control coupon was membranes, and highly reactive intermediates such asimmersed, changed its color from clear to dark Cr5+ stabilized by alpha hydroxyl carboxylates andbrown indicating the presence of corrosion Cr4+ are genotoxic and react either directly or throughproducts of iron. On the other hand, the color of free radical intermediates to damage DNA [8-13].salt solutions of molybdenum esters of gluconate The International Agency for Research on Cancersalts changed from clear to yellow and the salt (IARC) has determined that Cr(VI) is carcinogenic tosolution of vanadium ester of potassium benzilate humans. The World Health Organization (WHO) haschanged color from clear to light yellow indicating determined that Cr(VI) is a human carcinogen [14].some corrosion was taking place. In addition to The Department of Health and Human Servicesvisual observations revealing the extent of (DHHS) has determined that certain Cr(VI)corrosion qualitatively, the pH, conductivity and compounds (calcium chromate, chromium trioxide,oxidation-reduction potential of the immersion lead chromate, strontium chromate, and zincsolutions were measured with respective probes chromate) are known human carcinogens [15].prior to and after the immersions and relevant Finally, the EPA has classified Cr(VI) as a Group A,conclusion made extensively to propose the known human carcinogen by the inhalation route ofchemical mechanisms with regards to the exposure [16-21].inhibitors used for corrosion inhibition of mild However, despite their negative aspects, tosteel alloy. Inhibitors used were previously date, no replacements exist in the market forsynthesized by the author as replacements for carcinogenic chromates with the same efficiency forcarcinogenic hexavalent chromium inhibitors. a range of aluminum alloys and steel, neither asSyntheses and characterization studies of the pigment nor as a metal pretreatment [22-23]. Givennovel environmentally friendly corrosion the toxicity and carcinogenicity of chromates, theinhibitors, the results of weight-loss tests purpose is not only to synthesize and characterizeperformed to obtain the inhibition efficiencies of efficient corrosion inhibitors for certain alloys ofthese inhibitors and characterization studies of the certain metals to be applied in differentsubstrate surfaces immersed in aqueous inhibitor environments, but also to find environmentallysolutions by means of different surface techniques friendly corrosion inhibitors for successful chromatesuch as FT-IR, X-Ray, SEM, XPS and digital replacements. In this regard, the standard for animaging were reported in author’s various work environmentally friendly inhibitor is considered aselsewhere in the literature. having acceptable or no toxicity compared toKey words: carcinogenic, characterization, chromate inhibitors. Studying the reasons underlyingconversion coating, immersion, substrate the success of chromate inhibitors seemed to be the first reasonable approach one might take before1. INTRODUCTION formulating chromate replacements, e.g., synergistic The mobility of aqueous Cr 6+ within combinations of oxyanion analogues of chromatesbiological systems and its reactivity with biochemical with those of hydroxyacids and metal cations that areoxidation mediators make it highly toxic, known for their corrosion inhibiting efficiencies 1455 | P a g e
  2. 2. Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1455-1461having the general formula of addition of an oxidizer will raise the ORP value,(M)x(hydroxyacid)y(M‘aOb)z, which constituted the while the addition of a reducer will lower the ORPfirst phase of this research by the author [24]. value.Syntheses and chacaterization work was followed up The ORP values of immersion solutionswith the weight-loss tests to obtain the inhibition were measured to determine whether the redoxefficiencies of respective inhibitors, while in this capable inhibitor compounds had gone thorugh redoxstudy, aqueous immersion solutions of novel reactions or not. Dissolved oxygen may be reducedenvironmentally friendly corrosion inhibitors that are by the metal substrate and leading to lowering of theused to inhibit corrosion of mild steel substrate ORP value but comparison to the control solutionsurfaces in corrosive media are characterized. should negate this effect. Overall, the ORP values were decreased in2. CHARACTERIZATION OF IMMERSION average by half during immersions for both the SOLUTIONS control and inhibitor containing solutions. The Immersion solutions are indicators of the exceptions were the gluconate salts of zinc andextent of corrosion, which can even be observed calcium, and their vanadate esters, where only avisually in a qualitative manner, e.g. salt solutions of slight decrease in ORP occurred. As expected,gluconate salts remained clear throughout the inclusions of salt ions into the immersion solutionsimmersion of mild steel coupons, while the salt and increasing the immersion period led to furthersolution in which the control coupon was immersed, decrease in ORP.changed its color from clear to dark brown indicating In contrast to the molybdenum esters ofthe presence of corrosion products of iron. On the gluconate salts, the ORP values for immersionother hand, the color of salt solutions of molybdenum solutions of vanadium esters of gluconates did notesters of gluconate salts changed from clear to yellow decrease. The amount of slight decrease or evenand the salt solution of vanadium ester of potassium increase was approximately the same for allbenzilate changed color from clear to light yellow vanadium esters regardless of whether the hydroxy-indicating some corrosion was taking place. In acid constituent was gluconate or benzilate with theaddition to visual observations revealing the extent of exception of zinc salts of vanadium esters, in whichcorrosion qualitatively, the pH, conductivity and slight increases in ORP have been observedoxidation-reduction potential of the immersion compared to almost no decrease to very littlesolutions were measured with respective probes prior decreases when calcium and potassium cations wereto and after the immersions and relevant conclusion in the formulation, respectively. These results weremade extensively to propose the chemical unusual considering the decrease in ORP values ofmechanisms with regards to the inhibitors used for the control solutions and the immersion solutions ofcorrosion inhibition of mild steel alloy. Inhibitors other tested inhibitor compounds that had similarused were previously synthesized by the author as inhibition efficiencies. Qualitative analyses of thereplacements for carcinogenic hexavalent chromium vanadium ester treated coupons revealed clearinhibitors. Syntheses and characterization studies of surfaces with no uniform corrosion except a few pits.the novel environmentally friendly corrosion In the IR spectra of coupons treated with vanadateinhibitors, the results of weight-loss tests performed esters, contained absorptions that might have beento obtain the inhibition efficiencies of these inhibitors due to vanadium oxides in the low frequency regionand characterization studies of the substrate surfaces of 400 cm-1 to 1000 cm-1, but these were not resolvedimmersed in aqueous inhibitor solutions by means of sufficiently to deduce such a conclusion. Overall, thedifferent surface techniques such as FT-IR, X-Ray, vanadates seemed to work similarly to chromates;SEM, XPS and digital imaging were reported in however any conversion coating that might beauthor’s various work elsewhere in the literature. formed is either not adherent to the substrate surfaceThree aluminum alloys were chosen for the corrosion or not resistant to the cleaning solution of 50%inhibition tests in aqueous environments that are hydrochloric acid. In agreement with the results forAluminum 2024, 6061, and 7075 alloys due to their the vanadium esters, the ORP values of thecommon use in industry and, specifically, in aircrafts. immersion solutions of calcium and zinc gluconate Characterization of the immersion solutions salts did not decrease as opposed to magnesium andwas conducted using oxidation-reduction potential, sodium gluconate salts, which showed significantpH and conductivity probes. Two readings were decrease. The zinc salt had the lowest decrease of alltaken per sample, one before immersion and another of the gluconates. Since all gluconate salts hadafter completion of immersion. similar high inhibition efficiency values, the difference in ORP values is likely due to the cathodic2.1. ORP MEASUREMENTS inhibitive properties of zinc and calcium cations ORP is proportional to the concentration of resulting in precipitation of zinc and calciumoxidizers or reducers in a solution, and their activity hydroxides at cathodic sites.or strength. It provides an indication of the solutionsability to oxidize or reduce another material. The 1456 | P a g e
  3. 3. Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1455-1461 zinc and calcium gluconates boronglucos eFigure 1 ORP (Oxidation-Reduction Potential) vs. Time Graph of Immersion Solutions of Various InhibitorsDuring Immersions of CouponsBelow ΔORP graph indicates the majority of corrosion inhibiting compounds’ ORP values lowered by anaverage of roughly 350 mV. vanadate esters, zinc and calcium gluconatesFigure 2 ΔORP vs. Time Graph of Immersion Solutions of Various Inhibitors During Immersions of CouponsThe ΔORP vs IE graph shown below indicates that the majority of the compounds that had ORP valuesdecreased by an average of ~350 mV had positive inhibition efficiencies in the range of 50% to 100%. 1457 | P a g e
  4. 4. Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1455-1461Figure Error! No text of specified style in document. ΔORP vs. Inhibition Efficiency Graph of ImmersionSolutions of Various InhibitorsThe ΔORP/ORPinitial vs IE graph below indicates that the average ORP values were roughly halved for over 100tested compounds with the exception of zinc and calcium gluconates and the vanadate esters.Figure 4 ΔORP/ORPinitial Ratios vs. Inhibition Efficiency Graph of Immersion Solutions of VariousInhibitorsThe vast majority of the ORP values were found to be within the range of 200 mV and 500 mV with theexceptions of the immersion solutions with various concentrations of calcium or zinc gluconate salts and theboroglucose solution which had an ORP value down from 600 mV to almost 0 mV. ORPfinal vs IE 150 100 zinc and calcium 50 boronglucos gluconates e 0 IE -50 0 100 200 300 400 500 600 700 800 -100 -150 -200 ORPfinal(mV)Figure 5 Final ORP Values vs. Inhibition Efficiency Graph of Immersion Solutions of Various Inhibitors2.2. PH GRAPHSIn acidic solutions an increase in pH occurs due to hydrogen evolution caused by the reduction of hydroniumions. In near neutral to basic solutions, the system chosen for this study, the pH also increases due to the anodicreaction of corrosion process, that is O2 + 2H2O + 4e- 4OH-, (Eq. 1)Accordingly, pH of the immersion solutions of good inhibitors increased only slightly, while a large increasewas observed for compounds with poor corrosion inhibition ability. One week immersion solutions containing 1458 | P a g e
  5. 5. Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1455-1461boroglucose, borogluconate, and the molybdenum esters of gluconate salts had higher ΔpH and final pH valuesthan the other tested compounds. This is also correlated with the trends observed by ORP measurements. molybdat organic es acidsFigure 6 ΔpH vs. Time Graph of Immersion Solutions of Various Inhibitors During Immersions of CouponsOn the other hand, the gluconate salts and vanadium esters of gluconate salts had either very little increase orvery little decrease in their pH values, again agreeing with the ORP measurements and inhibition efficiencyresults. Overall, the ΔpH values were within ~ -0.2 and 2.6. The final pH values vs IE and ΔpH/pHinitial values vsIE graphs did not reveal any other trends other than the aforementioned ones.2.3. CONDUCTIVITY GRAPHS inhibitor present during the second immersion The conductivities of the immersion solutions period. These results are in harmony with theinitially originated mainly from the initially present inhibition efficiency results suggesting the totalinhibitor concentration of 200 ppm and the 60 ppm consumption of the inhibitors and precipitation ofchloride. However, as the corrosion and corrosion ions originated from corrosion reactions leading toinhibition processes took place many other a lower final conductivity. The exception to thisproducts contributed to the final conductivity trend was the immersion solution of thevalues. Al(gluconate)2OH treated coupon, which revealed aMost decreases in conductivity occurred for slight increase in conductivity in harmony with theimmersions of 10 and 14 day periods with no inhibition efficiency results. 1459 | P a g e
  6. 6. Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1455-1461 chromium acetateFigure 7 Δσ (Conductivity) vs. Time Graph of Immersion Solutions of Various Inhibitors during Immersions ofCouponsThe immersion solutions with high inhibition efficiencies revealed no or slight positive increases in theirconductivities. This included one week immersion solutions of gluonate salts and their esters in general. Theimmersion solution of chromium acetate revealed the only out of trend result with the highest increase inconductivity. Notably, the inhibition efficiency of chromium acetate treated mild steel coupon was also highlynegative. chromium acetateFigure 8 Δσ (Conductivity) vs. Inhibition Efficiency Graph of Immersion Solutions of Various InhibitorsMost of the final conductivity values were within the range of 100 μS to 200 μS, close to the initial conductivityvalues. Plotting final conductivity values vs IE and Δconductivity/initial conductivity values vs IE did not revealother trends but the aforementioned ones.3. CONCLUSIONS substrate. Successful inhibitors such as gluconates Oxidation-reduction potential, pH, and and borates repaired the protective oxide film onconductivity measurements of immersion solutions mild steel substrates either by adsorbing onto thebefore and after completion of immersions revealed substrate surface and preventing aggressive anionsvaluable characterization results supplementary to to be adsorbed via competitive adsorptionweight-loss test results. In the light of these mechanism or by forming mild strength complexescharacterizations, the proposed inhibition with iron cations leading to an incompletemechanism of the synergistic formulations of corrosion cell thus preventing further corrosion orhydroxy-acids and metal oxyanions was based on by incorporating into the protective oxide film andthe repair of the protective oxide films on the metal repairing defective sites. 1460 | P a g e
  7. 7. Volkan Cicek, Mehmet Ozdemir / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 3, Issue 1, January -February 2013, pp.1455-1461However, a mechanism favored by several authors [13] Stearns, D.; Wetterhahn, K. (1994)in the literature, that is formation of insoluble iron Chemical Research Toxicology, 7, 219.gluconate complexes on the metal substrate did not [14] Occupational Safety and Healthseem to be possible at least not for a considerable Administration (OSHA) (1998)period of time given the aggressive conditions of Occupational Safety and Healththe media. Standards, Toxic and Hazardous Substances, Code of Federal Regulations,4. ACKNOWLEDGEMENTS 29 CFR 1910.1000.Assoc. Prof. Dr. Allen Apblett is acknowledged for [15] World Health Organization (1998)the expertise and knowledge he provided me during Chromium, Environmental Health Criteriamy PhD education making it possible for me to 61, Geneva, Switzerland.proceed further in research and science. Also, Ishik [16] Lay, P.; Levina, A. (1998) Journal of American Chemical Society, 120, 6704. [17] U.S. Environmental Protection AgencyUniversity is acknowledged for the financial (1998) Toxicological Review ofsponsorship provided for this project. Hexavalent Chromium, National Center for Environmental Assessment, Office ofREFERENCES Research and Development, Washington, [1] Bardal, E. (2003) Corrosion and DC. Protection, Springer, 154. [18] U.S. Environmental Protection Agency [2] Clark, W. J.; McCreery, R. L. (2002) (1999) Integrated Risk Information Journal of Electrochemical Society, 2002, System (IRIS) on Chromium, VI, National 149, B379. Center for Environmental Assessment, [3] Osborne, J. H.; Du, J.; Nercissiantz, A.; Office of Research and Development, Taylor, S. R.; Bernard, D.; Bierwagen, G. Washington, DC. P. (2000) Advanced Corrosion-Resistant [19] U.S. Department of Health and Human Aircraft Coatings, prepared under contract Services (1993) Registry of Toxic Effects no. F33615-96-C-5078, Dayton, OH, of Chemical Substances (RTECS) online Wright-Patterson AFB, Air Force Material database, National Toxicology Command. Information Program, National Library of [4] Kending, M. W.; Buchelt, R. G. (2000) Medicine, Bethesda, MD. Corrosion Inhibition of Aluminum and [20] American Conference of Governmental Aluminum Alloys by Soluble Chromates, Industrial Hygienists (ACGIH) (1999) Chromate Coatings, and Chromate-Free TLVs and BEI,. Threshold Limit Values Coatings, Corrosion, 59, 379-400. for Chemical Substances and Physical [5] Lunn, G.; Sansone, E. B. (1990) Agents, Biological Exposure Indices, Destruction of Hazardous Chemicals in Cincinnati, OH. the Laboratory, Toronto, John Wiley & [21] National Institute for Occupational Safety Sons, 63-66. and Health (NIOSH) (1997) Pocket Guide [6] Sax, N. I.; Lewis, R. J. Sr. (1989) to Chemical Hazards, U.S. Department of Dangerous Properties of Industrial Health and Human Services, Public Health Materials, 7th ed., New York, Van Service, Centers for Disease Control and Nostrand Reinhold, 2, 912913. Prevention Cincinnati, OH. [7] Becker, G. (1969) Arch.Eisenhuettenwes., [22] Specialty Chemicals Magazine (2001) A 40, 341. New Class of Corrosion Inhibitor, Bricorr [8] Metroke, T. L.; Gandhi, J. S.; Apblett, A. 288. (2004) Corrosion Resistance of Ormosil [23] Metroke, T. L.; Parkhill, R. L.; Knobbe, E. Coatings on 2024-T3 Aluminum Alloy, T. (2001) Passivation of Metal Alloys Progress In Organic Coatings, 504, 231-- Using Sol-Gel Derived Materials-a 246. Review, Progress in Organic Coatings, 41, [9] O’Brien, P. O.; Kortenkamp, A. (1995) 233-238. Transition Metal Chemistry, 20, 636. [24] V. Cicek, A. Apblett, Synthesis and [10] International Agency for the Research on Characterization of Salts and Esters of Cancer (1990) Chromium and Nickel Hydroxy Acids as Corrosion Inhibitors for Welding in Monographs on the Evaluation Mild Steel and Aluminum Alloys, J. of Carcinogenic Risks to Humans, Lyon, Chem. Chem. Eng., 5, 2011, 112-116. France, 49. [11] Suzuki, Y. (1990) Ind. Health, 28, 9. [12] Suzuki, Y.; Fukuda, K. (1990) Arch. Toxicology, 64, 169. 1461 | P a g e

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