Sains Malaysiana 40(9)(2011): 953–957
Inhibitive Behaviour of Corrosion of Aluminium Alloy in
NaCl by Mangrove Tannin
(Kelakuan Perencatan
Kakisan Aloi Aluminium di dalam NaCl oleh Tanin Bakau)
Solhan Yahya*, Afidah Abdul Rahim, Affaizza Mohd Shah
& Rohana Adnan
Pusat Pengajian Sains Kimia, Universiti Sains Malaysia
11800 USM, Pulau Pinang, Malaysia
Received: 16 June 2010 / Accepted: 14 March 2011
ABSTRACT
Anticorrosion potential of
mangrove tannins on aluminium alloys AA6061 in NaCl solution has been studied
using potentiodynamic polarisation method and scanning electron microscopy (SEM).
The study was carried out in different pH of corrosive medium in the absence
and presence of various concentrations of tannin. The corrosion inhibition
behaviour of the mangrove tannin on AA6061 aluminium alloy corrosion was found
to be dependant on the pH of NaCl solution. Our results showed that the
inhibition efficiency increased with increasing tannins concentration in
chloride solution at pH 6. Treatment of aluminium alloy 6061 with all
concentrations of mangrove tannins reduced the current density, thus decreased
the corrosion rate. Tannins behaved as mixed inhibitors at pH 6 and reduction
in current density predominantly affected in cathodic reaction. Meanwhile, at
pH 12, addition of tannins shifted the corrosion potential to more cathodic
potentials and a passivating effect was observed in anodic potentials. SEM studies
have shown that the addition of tannins in chloride solution at pH 12 reduced
the surface degradation and the formation of pits.
Keywords: Corrosion;
inhibition efficiency; potentiodynamic polarisation; tannin
ABSTRAK
Potensi tanin bakau sebagai
antikakisan bagi aloi aluminium AA6061 di dalam larutan NaCl telah dikaji
menggunakan teknik piawaian, iaitu kaedah pengutuban potensiodinamik dan
mikroskopi elektron imbasan (SEM). Kajian telah dijalankan
di dalam larutan NaCl pada pH berbeza dengan kehadiran pelbagai kepekatan
ekstrak tanin. Kelakuan perencatan kakisan bagi aloi aluminium didapati
bergantung pada pH larutan NaCl. Keputusan menunjukkan kecekapan perencatan
kakisan meningkat dengan peningkatan kepekatan tanin di dalam NaCl pada pH 6.
Perawatan aloi aluminium dengan semua kepekatan tanin bakau telah mengurangkan
ketumpatan arus yang seterusnya merendahkan kadar kakisan. Tanin bertindak
sebagai perencat jenis campuran di dalam NaCl pada pH 6 dan penurunan
ketumpatan arus kakisan didominasi oleh tindakbalas katodik. Sementara itu,
pada pH 12, penambahan tanin telah menganjak keupayaan kakisan kepada keupayaan
yang lebih katodik dan kesan pempasifan telah diperhatikan pada keupayaan
anodik. Kajian SEM menunjukkan penambahan tanin di
dalam larutan NaCl pada pH 12 telah mengurangkan degradasi permukaan aloi
aluminium dan pembentukan liang.
Kata kunci: Kakisan; kecekapan perencatan; pengutuban
potensiodinamik; tannin
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*Corresponding author; email: solhan_156@yahoo.com
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