CORROSION RESISTANCE OF HIGH MANGANESE COPPER ALUMINIUM ALLOYS IN SEA WATER

Abstract

Introduction The degree of adsorption of organic inhibitors on a metal surface in presence of halide anion is predominantly influenced by the synergistic effect. The synergistic effect brings about an improvement in inhibition as a result of chemisorption or physical adsorption depending on the nature of the interaction between the halide and the cation of the inhibitor. This effect is partly attributed to the stabilization of the adsorbed anion layer by an organic cation through a possible covalent linkage. The degree of availability of electrons influences the mode of adsorption. Investigations on ferric ion corrosion have shown that the synergistic inhibition effects the corrosion processes by primarily increasing the polarization of the cathodic reaction. The adsorption of quinoline on 18–8 steel in the presence of halider ions is predominantly influenced by the synergistic effect. It has been found that the addition of smaller concentration of quinoline inhibits the cathodic reaction and higher concentrations of quinoline inhibit the anodic reaction as well. According to Iofa the formation of an adsorbed layer of positively charged ion retards the transfer of cation through a binary layer and lowers the transfer rate. Work on amines has shown that tertiary and secondary amines are stronger than the primary amines as a result of increase of dipole moment of the doublet, increase of ionisation energy and increase of polarizability. Basicity and stearic effects, both are important. The high effectiveness of cyclic amines with more than seven carbon atoms appears to be correlated with the character of the free electron. It has been shown that whereas the organic compounds of cationic type were weakly absorbed on the iron surface in H2SO4 the addition of halides produced a considerable increase in the adsorption. Cavallaro and others have shown that several nitrogen molecules inhibit both the anodic and cathodic reactions.

Citation

AHMAD, Z., GHAFELEHBASHI, M. and NATEGH, S. (1974), "CORROSION RESISTANCE OF HIGH MANGANESE COPPER ALUMINIUM ALLOYS IN SEA WATER", Anti-Corrosion Methods and Materials, Vol. 21 No. 8, pp. 13-17. https://doi.org/10.1108/eb006957