Abstract
The influence of pH on the corrosion behavior of Mg-based AZ91D alloy was investigated in a constant composition phosphate medium using various electrochemical techniques, complemented with surface analysis data. The studied solutions were 0.1 M H3PO4, NaH2PO4, Na2HPO4 and Na3PO4 having pH values of 1.8, 4.5, 9.1 and 11.8, respectively. Spontaneous passivation was substantiated from monitoring the continuous positive shift of the open circuit corrosion potential with both immersion time and solution pH. The impedance data indicated more improvement in the insulating properties of the corrosion products formed on the alloy surface with increase in pH. The electrolyte pH plays a determinant influence on surface film properties, as films formed in phosphate solutions with higher pH values are thicker, thus affording better protection for the alloy than those formed in acidic solutions. Good agreement was observed between the results obtained from electrochemical techniques and those from EDX and XRD examinations. The alloy is more susceptible to corrosion in acidic phosphate solutions than in the alkaline ones. Crystalline magnesium (Mg), magnesium hydride (MgH2) and magnesium oxide (MgO) were found to be the main constituents of the surface film after holding for 2 h in the acidic phosphate medium.
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References
Ghali E, Dietzel W, Kainer KU (2004) J Mater Eng Perfor 13:7
Ghali E (2000) Magnesium and Magnesium alloys. In: Revie RW (ed) Uhlig corrosion handbook. Wiley, New York
Avedesian MM, Baker H (1999) Magnesium and magnesium alloys, ASM speciality handbook. ASM International
Chen J, Wang J, Han E, Dong J, Ke W (2005) J Mater Corros 57:789
Polmear IJ (1995) Light alloys: metallurgy of the light metals, 3rd edn. Butterworth, Heinemann, Oxford
Li GY, Lian JS, Niu LY, Jiang ZH, Jiang Q (2006) Surf Coat Technol 201:1814
Hsiao H, Tsai W (2005) Surf Coat Technol 190:299
Zhou W, Shan D, Han E-H, Ke W (2008) Corros Sci 50:329
Zhao M, Wu S, Luo J, Fukuda Y, Nakae H (2006) Surf Coat Technol 200:5407
Niu LY, Jiang ZH, Li GY, Gu CD, Lian JS (2006) Surf Coat Technol 200:3021
De Pauli CP, Giordano MC, Lopez BA, Manzur E (1988) Corros Sci 28:769
Ismail KM, Virtanen S (2007) Electrochem Solid-State Lett 10:C9
El-Taib Heakal F, Ghoneim AA, Fekry AM (2007) J Appl Electrochem 37:405
Baril G, Blanc C, Pébère N (2001) J Electrochem Soc 148:B489
Bialkowski SE, http://www.chem.usu.edu/~sbialkow/Classes/3600/Overheads/H3A/H3A.html
Melendres CA, Camillone A, Tipton T (1989) Electrochim Acta 34:281
Chen J, Wang J, Han E, Dong J, Ke W (2007) Electrochim Acta 52:3299
Macdonald JR (ed) (1987) Impedance spectroscopy: emphasizing solid materials. Wiley, New York
Leibig M, Halseg T (1993) Electrochim Acta 38:1985
Benederti AV, Symodjo PTA, Nobe K, Cabot PL, Proud WG (1995) Electrochim Acta 40:2657
El-Taib Heakal F, Fekry AM, Ghoneim AA (2008) Corros Sci 50:1618
Zhang LJ, Fan JJ, Zhang Z, Cao FH, Zhang JQ, Cao CN (2007) Electrochim Acta 52:5325
Pourbaix M (1974) Atlas of electrochemical equilibria in aqueous solutions. NACE International, Houston, p 139 and p 168
Ambat R, Aung NN, Zhou W (2000) J Appl Electrochem 30:865
Uhlig HH, Winston R (1985) Corrosion and corrosion control. Wiley, New York (Chap. 20)
Chen J, Wang J, Han E, Ke W (2007) Corrosion 63:661
Nordlien JH, Nisancioglu K, Ono S, Masuko N (1996) J Electrochem Soc 143:2564
Hawke DL, Hillis JE, Pekguleryuz M, Nakatsugawa I (1999) In: Avedesian MM, Baker H (eds) Magnesium and magnesium alloys. ASM International, Materials Park, OH, p 194
Perrault GG (1974) J Electroanal Chem 51:107
Hubschmid C, Landolt D, Mathieu HJ (1995) Fresenius J Anal Chem 353:234
Baril G, Blanc C, Keddam M, Pébère N (2003) J Electrochem Soc 150:B488
Ballerini G, Bardi U, Bignucolo R, Ceraolo G (2005) Corros Sci 47:2173
Lunder O, Lein JE, Aune TK, Nisancioglu K (1989) Corrosion 45:741
Song G, Atrens A, Dargusch M (1999) Corros Sci 41:249
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El-Taib Heakal, F., Mohammed Fekry, A. & Ziad Fatayerji, M. Electrochemical behavior of AZ91D magnesium alloy in phosphate medium—part I. Effect of pH. J Appl Electrochem 39, 583–591 (2009). https://doi.org/10.1007/s10800-008-9696-y
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DOI: https://doi.org/10.1007/s10800-008-9696-y