YULI YETRI1,*, EMRIADI2,
NOVESAR JAMARUN2 , GUNAWARMAN3,*
1 Department
of Mechanical Engineering, Padang
State Politechnic, Limau Manis, Padang 25163, Indonesia
2Department
of Chemistry, Andalas University, Padang, Indonesia
3Department of Mechanical Engineering, Andalas University, Padang, Indonesia
ABSTRACT
The effects of Theobroma
cacao peels extract (TCPE) on corrosion inhibition of a 0.32%C mild steel in 1.5M NaCl solution was studied
using weight loss at various temperature, and potentiodynamic polarization and
electrochemical impedance spectroscopy (EIS) methods at room temperature and elevated
temperature. Electrochemical
polarization was conducted
to evaluate
the type of
inhibition. Infrared
spectra and phytochemicals test were
performed to determine the chemicals constituent in the extract of cacao peels that play a role in the inhibition process. Sample surface morphology was observed by using a scanning electron
microscopy with energy
dispersive X-ray spectroscopy
(SEM-EDX). Experimental
results revealed that the corrosion
rate decreases with increasing
extract concentration, but it increases
with increasing temperature. The maximum corrosion
inhibition efficiency is relatively
high, that is 91.93%
(weight loss), 85.90% (Tafel), 90.19% (Rp) and 75.23% (EIS) at a
concentration of 2.5% the extract.
The increasing of inhibition efficiency is due to the increase of charge resistance
transfer (Rct) as a result of chemical adsorption in the surface. Chemical adsorption occurs
on the surfaces obeys Langmuir isotherm adsorption,
with an indication of adsorption unimoleculer. The polarization
curve shows the inhibitor
behaves as a
mixed inhibitor with the dominant cathodic
inhibition. The use of polar extract of Theobroma cacao
peels as
inhibitor is
quite effective in
reducing corrosion attack
of
NaCl solution
on the mild steel.
Key word:
Theobroma cacao peels extract (TCPE), Corrosion inhibitor, NaCl, Corrosion rate, Mild steel
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