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Studies of zinc corrosion inhibition using Zr-MCM-41 inorganic membrane
International Islamic University Malaysia
Department of Manufacturing and Materials Engineering
Kulliyyah of Engineering, International Islamic University Malaysia
Zinc corrosion in alkaline potassium hydroxide electrolyte (KOH) (1 – 8 M) has been studied using three different methods, namely, weight loss method, Tafel extrapolation and open circuit potential (OCP)-time transient profile. In weight loss method, zinc corrosion rates are measured from various immersion times i.e. one until seven days. It is observed that zinc corrosion rates data obtained after an exposure time of 120 hours is the most optimum. The accuracy of Tafel extrapolation method relies on the accurate determination of the linear regions from the polarization branches. In order to eliminate the ambiguity in the linear extrapolation, this work develops a quantitative method based on piecewise linear regression analysis. In this method, the entire polarization data is divided into small sub-intervals and variation in the regression coefficient and linearity coefficient values are observed. Consistency in these values serves as a quantitative indicator of the linear Tafel regions. Using the Tafel extrapolation method, the trend of zinc corrosion in KOH electrolyte is found to be comparable to that obtained from the weight loss method, except in 8-M KOH. For KOH molarity of 1-5 M, the zinc corrosion rates are measured 1.6 to 1.8 times higher than the values obtained from the weight loss measurement. Comparing with the OCP-time transient profiles, a slightly different trend in the tendency of zinc to corrode is observed. The efficacy of zirconia as zinc corrosion inhibitor in KOH electrolyte is studied using the OCP relaxation profiles. Rather than employing the corrosion inhibitor either into the electrolyte or as one of the components in the electrode formulation, zirconia is incorporated into the structure of MCM-41 membrane separator. MCM-41 material consists of arrays of silica-based, hexagonal nano-channels. The corrosion inhibition activity of Zr-MCM-41 membrane is studied with varying zirconia content i.e. 3 wt.%, 7 wt.% and 11 wt. %. The efficiency of the zinc corrosion inhibition increases with higher zirconia wt. %, however, in KOH of 1 M and 7 M, higher amount of zirconia is required to supress the zinc corrosion.
Thesis (MSMAT)--International Islamic University Malaysia, 2014.
Includes bibliographical references (leaves 78-82).