Electrochemical Behavior Of Coper In Nitric Acid Solution:

Reda El-hassanin El-hassanin Abo El-dahab

Corrosion is a major issue for the increase of service life and reliability of metallic materials. A detailed understanding of the mechanisms of corrosion helps us to solve existing corrosion problems and to prevent future problems. This work discusses the corrosion inhibition of copper in nitric acid solution.This work contains three chapters:Chapter one ”Introduction”This chapter includes different theories of corrosion, causes of corrosion, forms of corrosion, corrosion inhibition and types of inhibitors, and literature survey on corrosion of copper in acid medium.Chapter two” Experimental Techniques”It includes the chemical composition of the investigated material, preparation of the used nitric acid solution, and procedures used for the corrosion measurements such as a weight loss and electrochemical techniques.Chapter three” Results and Discussion”It deals with the results obtained and their discussion and this chapter is divided into three sections:First Section:1) The inhibition efficiency of quinazoline compounds toward the corrosion of copper in 2MHNO3 was calculated using weight loss method measurements. The inhibition efficiency of there compounds increases with increasing the inhibitor concentrations. The order of inhibition efficiency decreases in the following order:5 > 4 > 3 > 2< 1.2) The degree of surface coverage (θ) for the inhibitors on the metal surface increases with increasing the concentration in the corrosive medium. The action of the inhibitors in the aggressive acid was assumed to be due to their adsorption at the metal /solution interface. The adsorption process obeys Frumkin’s isotherm.3) The effect of temperature on the corrosion inhibition of copper in 2M nitric acid was determined over the temperature range 30-500 C using weight loss measurements. The rate of corrosion increases with increasing the temperature together with decrease in inhibition efficiency indicating that the inhibition occurs through physical adsorption of the additives. Thermodynamic functions of activation were calculated in presence of 13x10-6 M of quinazoline compounds.4) Synergistic effect of quinazoline compounds with KBr or KCl on copper corrosion inhibition in 2M nitric acid was studied. The results indicate that the inhibition efficiency increased in presence of 10-4 M of each of these anions. The adsorption ability on the copper surface was decreases in the following order KBr < KCl.Second Section:The effect of quinazoline compounds on the anodic and cathodic polarization of copper electrode in 2M HNO3 solutions was investigated. The corrosion rate (Icorr) was found to decreased with increasing of concentration of the additives. The polarization curves indicate that these compounds influence both anodic and cathodic processes (i.e. mixed inhibitors). The order of inhibition efficiency decreases in the following order5 > 4 > 3 > 2 > 1.Third Section:In this section potentiodynamic anodic polarization curves of copper electrode in 2M HNO3 at different concentrations of NaCl solution