Pitting corrosion inhibition of some copper alloys in NaCl solutions by straight chain carboxylates

Abstract

ELECTROCHEMICAL methods were used to investigate the abilities of the homologous straight chain monocarboxylates (CnH 2n+1COO-, n=l-13) to inhibit the pitting corrosion of two types of copper alloys in NaCl solutions. The copper alloys were alloy (I) (Cu + 4.47% Fe) and alloy (II) (Cu + 10.67% Al + 5.02% Fe). It was found that these were susceptible to pitting corrosion in NaCl solutions, with increase of C - ions concentration. Alloy (II) was more susceptible to pitting corrosion than alloy (1). The inhibition performance of the monocarboxylates was critically dependent upon their chain length. The range of chain lengths producing optimal inhibition efficiency was (6 ≤ n ≤ 10). These carboxylates showed abrupt decreases in inhibitor ability outside the optimal range. The dramatic variations in inhibition efficiencies probably resulted from competing reactions such as adsorption, solubility and micelle formation.