Abstract
The dissolution of the copper in naturally aerated HCl solution is studied at different acid concentrations using open circuit potential measurements, weight loss measurements, and galvanostatic polarization techniques. The rate of corrosion of the metal depends on acid concentration. Henna leaves (Lawsonia inermis L) extract is used as a naturally corrosion inhibitor for the corrosion of Cu in 0.5 M HCl solution. The inhibition efficiency of the henna extract depends on its concentration. Lower concentrations of the extract (2-4%) cause slight effect on metal dissolution. In presence of 6% of the extract, a competitive process occurs between metal dissolution and metal inhibition. However, higher concentrations of the extract 10% caused marked inhibition of the metal (58.7%). Inhibition of Cu dissolution in HCl solutions is assumed to be due to the formation of a Cu2+ -Lawsone complex on the anodic sites and the possible precipitation of Cu(OH)(2) on the cathodic sites of the metal surface.