Malaysian Journal of Analytical Sciences Vol 21 No 2 (2017): 346 - 355

DOI: https://doi.org/10.17576/mjas-2017-2102-09

 

 

 

A COMPARATIVE STUDY ON THE INHIBITORY ACTION OF SOME GREEN INHIBITORS ON THE CORROSION OF MILD STEEL  IN HYDROCHLORIC ACID MEDIUM

 

(Kajian Perbandingan Tindakan Rencatan oleh Perencat Hijau ke atas Pengaratan Keluli Lembut di dalam Medium Asid Hidroklorik)

 

Moorthy Shyamala¹* and Arthanas Arulanantham²

 

¹Department of Chemistry,

Government College of Technology, Coimbatore-641013, Tamil Nadu, India

²Department of Chemistry,

 S.N.S College of Technology, Coimbatore-641013, Tamil Nadu, India

 

*Corresponding author: shyamphd@yahoo.com

 

 

Received: 24 February 2015; Accepted: 9 February 2017

 

 

Abstract

The inhibitive action of the extracts of three green inhibitors namely Adathoda vasica, Eclipta alba and Centella asiatica were investigated.  Polarization method indicates that the plant extracts are under mixed control i.e promoting retardation of both anodic and cathodic reactions. The impedance method reveals that charge-transfer process controls the corrosion of mild steel. The plant-extracts obeys Langmuir adsorption isotherm. Kinetics and reason for the corrosion inhibition or the nature of adsorption is clearly shown. Physisorption mechanism has been proposed for the inhibition action of these plant extracts. The protective film formed on the surface was confirmed by Scanning Electron Microscopy (SEM). From hydrogen permeation method, all the plant extracts were able to reduce the permeation current. Results obtained in all the methods are very much in good agreement with increasing inhibition efficiency in the order: Eclipta alba > Adathoda vasica  > Centella asiatica. Among the three plant extracts studied, the maximum inhibition efficiency was found in Eclipta alba which showed 99.6% inhibition efficiency at 8.0 % v/v concentration of the extract.

 

Keywords:  mild steel, corrosion inhibition, plant-extracts, hydrochloric acid, physisorption

 

Abstrak

Tindakan perencatan oleh tiga ekstrak perencat hijau iaitu Adathoda vasica, Eclipta alba dan Centella asiatica telah dikaji. Kaedah polarisasi menunjukkan bahawa ekstrak tumbuhan di bawah kawalan campuran akan menghasilkan tindak balas perencatan bagi kedua–dua anod dan katod. Kaedah galangan mendedahkan bahawa proses pemindahan cas mengawal kakisan terhadap keluli lembut. Bahan ekstrak tumbuhan mematuhi penjerapan isoterma Langmuir. Kinetik dan sebab bagi perencatan kakisan atau sifat penjerapan jelas dapat ditunjukkan. Tindakan perencatan dari ekstrak tumbuhan adalah dicadangkan sebagai mekanisma serapan fizikal. Filem pelindung yang terbentuk di permukaan telah disahkan melalui mikroskopi elektron pengimbasan (SEM). Melalui kaedah penyerapan hidrogen, semua ekstrak tumbuhan dikenalpasti dapat mengurangkan penelapan arus. Keputusan yang diperolehi dalam semua kaedah amat bersetuju dengan peningkatan kecekapan rencatan adalah mengikut tertib iaitu Eclipta alba > Adathoda vasica > Centella asiatica. Di antara ketiga–tiga ekstrak tumbuhan yang dikaji, kecekapan rencatan maksimum diperolehi dari Eclipta alba iaitu 99.6% pada 8.0% v/v kepekatan ekstrak.

 

Kata kunci:  keluli lembut, perencat kakisan, ekstrak tumbuhan, asid hidroklorik, serapan fizikal

 

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