STUDIES ON THE CORROSION AND ELECTROCHEMICAL BEHAVIOUR OF SOME METALS

Abstract

From the previous survey it has been noted that the electrochemical behaviour of aluminium in alkaline solutions containing different NaN03 concentrations and nickel in formic, acetic, citric, oxalic and perchloric acid has not received much attention. For this purpose, the present study was undertaken to investigate the effect of NaN03 concentrations in alkaline solutions on the corrosion behaviour of aluminium under imposed current, anodic polarization of aluminium as well as the currentless behaviour of aluminium in these alkaline media. Anodic polarization measurements, direct determination ofthe corrosion rate from the weight loss technique as well as the measurement of the volume of hydrogen evolution have been applied. The effect of acid concentration on the open circuit potentials of the nickel electrode, the corrosion behaviour of nickel as well as potentiodynamic polarization curves for nickel electrode were recorded in order to achieve this aim.

Chapter I of this thesis is an introduction reviewing concisely the recent relevant literatures. The review includes the earlier investigations on the mechanism and kinetics of anodic dissolution of AI and Ni metals, anodic and cathodic polarization types of inhibitors, the phenomena of pitting, corrosion and corrosion inhibition, passivation, kinetics of formation of oxide films, the nature of the films formed on these metals and the beneficiation of the metaUmetal oxide formed.

Chapter II deals with the experimental part. It includes a description of the metal and electrode, specifications of the different chemicals used , the method of surface pre-treatment, the electrical lay out, cell and instruments for measurements of polarization, volume of hydrogen evolution and weight loss determination.