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