engleski

Comparison Of Some Natural Food Compounds Influence On Tin Dissolution

Our previous work 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. The corrosion rates and currents of tin samples in 50-500 ppm ascorbic acid (AA), 0, 5 - 2 g L-1 pectin and 0, 3% w/w NaCl model solutions, as well as NaCl solutions with AA/pectin addition were measured by the weight loss method. pH and conductivity changes during tin exposure to investigated solutions were determined. Mixtures of AA, pectin and NaCl were investigated as well using potentiostatic technique measurements. Using 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 AA and pectin adsorption on active sites on its surface. The inhibitor surface coverage was calculated and Tafel extrapolation results showed inhibitory effect of AA and NaCl-AA-pectin 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.

tin dissolution; natural inhibitors of corrosion; ascorbic acid; pectin

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