| Popis: |
Our previous work, as well as the literature data, showed that a variety of natural food compounds could slow down can corrosion process. In this work possible inhibitory effect of ascorbic acid and pectin on tin corrosion in salt solutions was studied. Based on our preliminary results, two different concentrations of ascorbic acid and pectin were chosen for further gravimetric and electrochemical investigation. The corrosion rates and corrosion current of tin samples in (50 and 200 ppm) ascorbic acid, (0.5 and 2) g dm-3 pectin and 0.3% NaCl model solutions, as well as NaCl solutions with ascorbic acid /pectin addition were determined by the weight loss method. Mixtures of (50, 100 and 200) ppm ascorbic acid, pectin and NaCl were investigated as well using potentiostatic technique measurements. By anodic dissolution measurements the amount of tin in model solutions after 1 hour exposure was calculated. The inhibition of the tin dissolution process can be explained by ascorbic acid and pectin adsorption on active sites on its surface. The inhibitor surface coverage was calculated and Tafel extrapolation results showed inhibitory effect of ascorbic acid and NaCl-pectin-ascorbic acid solutions on tin corrosion. Those results were plotted accorded to Langmuir isotherm and adsorption equilibrium constant was determined. According to Tafel extrapolation results it is shown that those model solutions form stable adsorbed film on metal surface. The synergistic effect of pectin and AA in the model solutions is noticed. It is assumed that chloride ion participate in competitive adsorption in the metal-electrolyte interface and tin corrosion takes place through the diffusion of corrosive media through film pores or when it was not covering all of the surface. |
