Malaysian Journal of Analytical Sciences Vol 18 No 3 (2014): 507 - 513

 

 

 

SCHIFF BASES DERIVED FROM ISATIN AS MILD STEEL CORROSION INHIBITORS IN 1 M HCl

 

(Bes Schiff Yang Terhasil Daripada Isatin Sebagai Perencat Kakisan Keluli Lembut Dalam 1 M Asid Hidroklorik)

 

Aliyin Abdul Ghani¹*, Hadariah Bahron¹, Mohamad Kamal Harun¹, Karimah Kassim²

 

¹Faculty of Applied Sciences,

²Institute of Science,

Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia

 

*Corresponding author: aliyinabdulghani@gmail.com

 

 

Abstract

Two Schiff bases namely, 3-(phenylimino)indolin-2-one (PII) and 3,3- (1,4-phenylenebis (azan-1-yl-1-ylidene))diindolin-2-one (PDI) were successfully synthesized from the condensation reaction giving yields of 72% and 84%, respectively. The ligands were characterized via physical and spectroscopic techniques namely melting point, Elemental Analysis (C, H, N), ¹H and ¹³C Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FTIR) Spectroscopy. The corrosion inhibiting property of the Schiff bases on mild steel in 1 M HCl solution were investigated by the weight loss measurements, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR). The concentrations of the Schiff bases were varied from 1 x 10^-3 M to 1 x 10^-5 M. The inhibition efficiencies obtained from all the methods employed were in good agreement where the percentage of inhibition efficiencies increased with concentration. Results showed that PDI was the better inhibitor with inhibition efficiency of 84% at 1 x 10^-3 M additive concentration.  This is likely due to the effect of its bigger molecular size, higher number of heteroatoms and bigger π-electron cloud of the conjugated double bond system.

 

Keywords: Schiff base, Isatin, Corrosion inhibitor, Mild steel, Hydrochloric acid

 

Abstrak

Dua bes Schiff, 3-(phenylimino)indolin-2-one (PII) dan 3,3- (1,4-phenylenebis (azan-1-yl-1-ylidene))diindolin-2-one (PDI) telah disintesis dengan jaya dari reaksi kondensasi memberikan hasil 72% dan 84%. Ligan-ligan telah dicirikan oleh pelbagai teknik kimia-fizikal seperti menentu takat lebur, analisis unsur, ¹H and ¹³C spektroskopi resonans magnet nuklear, dan spektroskopi inframerah. Ciri-ciri perencat kakisan bagi Bes Schiff di atas keluli lembut dalam 1 M asid hidroklorik telah dikaji melalui kaedah penghilangan jisim, spektroskopi impedans elektrokimia dan rintangan polarisasi linear. Kepekatan Bes Schiff disediakan dari 1 x 10^-3 M to 1 x 10^-5 M. Kecekapan perencat dari semua kaedah telah menunjukkan keserasian di mana peratus kecekapan perencat meningkat apabila jumlah kepekatan ligan bertambah. Keputusan menunjukkan PDI adalah perencat yang lebih baik dengan kecekapan perencat sebanyak  84% pada kepekatan 1 x 10^-3 M. Ini adalah kerana efek molekul yang lebih besar, jumlah heteroatom yang tinggi dan π-elektron yang lebih besar dari konjukasi system ikatan kembar.

 

Kata kunci: Bes Schiff, Isatin, Perencat kakisan, Keluli lembut, Asid Hidroklorik

 

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