?EFFECT OF CHROMATE, NITRITE AND BENZOATE IONS ADDITIVES ON THE CORROSION BEHAVIOUR OF LOW CARBON STEEL IN ACID MEDIUM

Abstract

The effect of CrO"4'N02 and C6HsCOO ions on the inhibitive behaviour of low carbon steel electrodes in aqueous
solutions of mono-, di-and tri-chloroacetic acids at pH 1to 4 is calculated by studying potential-time variation, weight
loss measurements and galvanostatic polarisation, It has been found that the steady state potentials which obey the re-
lationship E = a -b log C, where (a) is aproportional constant and (b) is the order of the reaction which can be obtained
from the linear plot of log C versus log corrosion rate which depend on the type of the acids and C is the molar
concentration of the acids, is shifted towards less negative values with the increase in the concentration of additive ions
and from pH 1 to 2 and then increases again at pH = 3 to 4. The decrease in the rate of corrosion with increase of anion
concentration is probably due to the fact that additive ions act as anodic inhibitors. The critical current density for
passivation varies with the nature and concentration of the additive anion.