Corrosion resistance of orthodontic wires made of thermo active alloy and SS 18/8 alloy in a beverage (hard drink) decreases on dilution with water

• G. Geetha¹, J.C. Angelin¹, S. Krishnaveni¹, N. Karthiga¹, J.M. Praveena¹, S. Rajendran¹ and J.A. Thangakani²

¹ Corrosion Research Centre, PG Department of Chemistry, St Antony’s College of Arts and Sciences for Women, Amala Annai Nagar, Tamaraipadi, Dindigul, Tamilnadu, India
² Department of Chemistry, The American College, Madurai, Tamil Nadu, India

Abstract: Corrosion resistance of SS 18/8 alloy and Thermo active alloy in various systems are compared. The various systems are (i) beverage alone, (ii) beverage+water and (iii) beverage+soda water system. Electrochemical study such as polarization study has been employed for this purpose. When Thermo active alloy is immersed in undiluted as such beverage, the corrosion potential is –319 mV vs SCE. The LPR value is 5.749·10⁷ Ohm·cm². The corrosion current is 0.7607·10^-9 A/cm². When beverage is diluted with water, the LPR value decreases from 5.749·10⁷ Ohm·cm² to 6.495·10⁶ Ohm·cm². It is inferred that when the beverage is diluted with water, the corrosion resistance of Thermo active alloy decreases. This is further supported by the fact, when water is added to the beverage, the corrosion current increases from 0.7607·10^-9 A/cm² to 6.533·10^-9 A/cm². Similarly when soda water is added to the beverage, the LPR value decreases from 5.749·107 Ohm·cm2 to 9.028·10⁶ Ohm·cm²; the corrosion current increases from 0.7607·10^-9 A/cm² to 4.077·10^-9 A/cm². Hence it is inferred that when Thermo active alloy is immersed in the diluted beverage, the corrosion resistance of Thermo active alloy decreases. When SS 18/8 alloy is immersed in undiluted as such beverage, the corrosion potential is –249 mV vs SCE. The LPR value is 3.609·10⁶ Ohm·cm². The corrosion current is 1.124·10^-8 A/cm². When beverage is diluted with water, the LPR value decreases from 3.609·10⁶ Ohm·cm² to 1.314·10⁶ Ohm·cm². It is inferred that when the beverage is diluted with water, the corrosion resistance of SS 18/8 alloy decreases. This is further supported by the fact, when water is added to the beverage, the corrosion current increases from 1.124·10^-8 A/cm² to 3.235·10^-8 A/cm². Similarly when soda water is added to the beverage, the LPR value decreases from 3.609·10⁶ Ohm·cm² to 1.098·10⁶ Ohm·cm²; the corrosion current increases from 1.124·10^-8 A/cm² to 4.189·10^-8 A/cm². Hence it is inferred that when soda water is added to the beverage, the corrosion resistance of SS 18/8 alloy decreases. Thermo active alloy is found to be more corrosion resistant in as such beverage than in beverage+water system or beverage+soda water system. SS 18/8 alloy is more corrosion resistant in as such beverage than in beverage+water system or beverage+soda water system. In as such beverage system, Thermo active alloy is more corrosion resistant than SS 18/8 system. In beverage+water system, Thermo active alloy is more corrosion resistant than SS 18/8 system. In beverage+soda water system, Thermo active alloy is more corrosion resistant than SS 18/8 system.

Keywords: сorrosion resistance, hard drink, beverage, polarization study, Thermo active Ni-Ti super elastic shape memory alloy, SS 18/8 alloy

Int. J. Corros. Scale Inhib., 2021, 10, no. 1, 388-398 PDF (447 K)
doi: 10.17675/2305-6894-2020-10-1-22

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