Inhibiting Effect of some Monosaccharides on the Corrosion of Copper in Nitric Acid

Abstract

A study has been made of the inhibitive efficiency of some monosaccharides (glucose, fructose, mannose, galactose, in the concentration range 10⁻³M–1·0M) on copper corrosion in HNO₃ (0·01, 0·1 and 1·0 M) at temperatures of 15°, 25° and 35°c. It was found that the structures of the various saccharides (pyranosic or furanosic) affected neither the efficiency nor the mechanism of inhibition. Inhibition was practically zero at concentrations of the monosaccharides between 10⁻³ and 10⁻¹ M, whereas, at 1·0 M, 65–70% inhibition was reached in 0·01 and 0·1 M HNO₃, and 50–60% in 1·0 M HNO₃.

In 1·0 M HNO₃ the saccharides act as cathodic inhibitors (reducing HNO₂ present in the HNO₃ solutions), whereas in 0·1 and 0·01 M HNO₃ they also acted as anodic inhibitors through theformation of an organometallic compound with Cu²⁺, which gave slight protection to the metal surface.