ELECTROCHEMICAL STUDIES ON CORROSION INHIBITION OF IRON

Abstract

The thesis comprises three main chapters:

The first chapter contains an introduction about the electrochemical nature and kinetics of corrosion. Corrosion inhibitors were defined and systematically classified. Experimental observation of corrosion inhibition and the effect of inhibitors on polarization behaviour were defined. Adsorption isotherms were discussed together with the effect of temperature on the action of inhibitors. The synergistic effect of anions on the acidic corrosion inhibition of iron and a literature survey on inhibition of iron corrosion in acidic and alkaline media were reviewed. Chapter II deals with the experimental chemical (weight-loss and thermometric ) and electrochemical ( potentiodynamic ) techniques used for measuring the corrosion rate and various electrochemical corrosion parameters of iron metal immersed in nitric, sulphuric acids ( 2M ) and in 2M sodium hydroxide solutions in the absence and in the presence of the

tested hydantoin compounds. The investigated compounds employed in this study as corrosion inhibitors were: ( i) Phenylhydantoin compounds:

3-ethylcarboxy-1-phenylhydantoin (A)

3-hydroxymethyl-1-phenylhydantoin ( B )

5-benzylidenehydantoin ( C )

1•phenylhydantoin ( D ) •' ( ii) Thiohydantoin compounds:

5-methyl-2-thiohydantoin (E)

I ,3-dimethyl-5-phenylazo-2- thiohydantoin ( F ) ( iii) Dithiohydantoin compounds: 5,5-dimethyl-2,4- dithiohydantoin ( G)