Pitting Corrosion Inhibition of Some Copper Alloys in Neutral Solutions by Straight Chain Carboxylates

S.S. Mahmoud,* M.M. Ahmed, A.H. Marie  and R.A. El-Kasaby

Chemistry Department, University College of Girls for Arts, Science and Education,

Ain shams University, Heliopolis, Cairo, Egypt

 

Received 10 January 2007; accepted 20 July 2007

 

 

Abstract

Electrochemical methods were used to investigate the abilities of the homologous straight chain monocarboxylates (C_nH_2n+1COO^-,n=1-13) to inhibit the pitting corrosion of two types of copper alloys in aerated, saline and near neutral aqueous 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 Cl^- ions concentration. Alloy (II) was more susceptible to pitting corrosion than alloy (I). The performance of monocarboxylates was shown to be critically dependent upon their chain length. The range of chain lengths producing optimal inhibition 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.

Keywords: adsorption, copper alloys, pitting corrosion, monocarboxylates, pola- rization, galvanic current, inhibition

 

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*Corresponding author. E-mail address: drsohairr@hotmail.com