Aminophenols as Corrosion Inhibitors for Aluminium–Copper Alloy in Sodium Hydroxide

Abstract

The inhibition by aminophenols of the corrosion of Al–4% Cu alloy (B26S) in solutions of sodium hydroxide has been studied in relation to the concentration of alkali and of inhibitor, the period of immersion and temperature. In general, at constant alkaliconcentration, inhibitor efficiency increases with concentration of inhibitor but, at constant inhibitor concentration, decreases with increase in alkali concentration, the effect being less pronounced with o-aminophenol. The inhibitive efficiency remains almost constant with temperature in the range 20–50°c, but decreases as the period of immersion is increased. At an inhibitor concentration of O·01–2·0% in 0·1 M NaOH the efficiency increases in the order: p-aminophenol < m-aminophenol < phenol < o-aminophenol.The inhibitors appear to function through adsorption following the Freundlich adsorption isotherm. The comparatively better inhibitive efficiency of o-aminophenol appears to be due to chelate formation. From galvanostatic polarisation data all thefour compounds appear to be mixed type inhibitors.