Abstract

INHIBITIVE PROPERTIES OF SODIUM MOLYBDATE -ZN2+ SYSTEM AND ITS SYNERGISM WITH GARLIC EXTRACT

R. Epshiba, A. Peter Pascal Regis*, C. Rajarathinam, R. Betsy Clarebel, S. Philomena Mary and J.K. Alphonsa Juliet Helina

ABSTRACT

The Inhibition efficiency (IE) of various concentrations of a Garlic Extract(GE)- SM(Sodium Molybdate) - Zn2+ system in controlling corrosion of mild steel immersed in well water was evaluated by a weight – loss study. The ternary system consisting of 100 ppm of SM and 25 pm of Zn2+ and 2 ml of GE is quiet effective and showed 76% IE. The influence of biocide SDS on the inhibition efficiency of SM-Zn2+-GE system has been investigated. Polarization studies reveal that SM - Zn2+- GE system functions as anodic inhibitor. AC impedance spectra suggest that a protective film is formed on the metal surface. The UV – visible absorption spectra indicates the possibility of formation of Fe2+-SM complex and Fe2+- allicin complex in the solution. FTIR spectra reveal that the protective film consists of Fe2+-SM complex and Fe2+- allicin complex and Zn(OH)2.

Keywords: Corrosion inhibition, carbon steel, sodium molybdate, garlic, synergistic effect