The Synergistic Effect Of Tannins And Iodide Ions On The Corrosion Inhibition Of Mild Steel In Corrosive Media
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Date
2014-02
Authors
Adam, Mohd Ridhwan
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The inhibition effect of mangrove tannin (MgT), mimosa tannin (MmT) and chestnut
tannin (CnT) on the corrosion behaviour of mild steel in 0.5 M HCl, 0.25 M H2SO4 and
3.5 % NaCl solutions was studied using weight loss, potentiodynamic polarisation and
electrochemical impedance spectroscopy (EIS) techniques. The results from all
techniques studied showed that MgT gave satisfactory inhibition efficiencies on mild
steel. The performance of MgT was further enhanced when iodide ions were added into
the corrosive media containing this inhibitor, indicating the occurrence of synergism
between these two compounds. In the weight loss analyses, the inhibition efficiencies for
all three tannins have been increased from 38-85 % to 82-97 % when iodide ions were
introduced into the corrosive media containing these inhibitors. The inhibition
efficiencies for all three tannins were enhanced from 47-89 % to 83-94 % when
combined with iodide ions in the potentiodynamic polarisation measurements. In the EIS
measurements, the inhibition efficiencies for all three tannins were further increased from
69-84 % to 80-92 % when these tannins were synergised by the iodide ions. The
inhibition efficiencies obtained from the weight loss and electrochemical measurements
were in good agreement. Potentiodynamic polarisation studies clearly revealed that MgT
behaved as mixed-type inhibitor with predominant anodic effectiveness. The Nyquist
plots obtained from the EIS analyses showed that the inhibition process was mainly
controlled by a charge transfer process.
Description
Keywords
Tannins And Iodide Ions , Mild Steel In Corrosive Media