Sodium- and chloride-selective microelectrodes optimized for corrosion studies

New sodium and chloride ion-selective membrane cocktails for glass-capillary microelectrodes were developed satisfying the demands for corrosion studies. Membrane cocktails were optimized to provide a wide pH working range, good long-term stability and reproducibility of potential. The proposed sodium-selective cocktail contains sodium ionophore VI, potassium tetrakis(4-chlorophenyl) borate and 2-nitrophenyl octyl ether. The chloride-selective cocktail consists of tridodecylmethylammonium chloride and 2-nitrophenyl octyl ether. The proposed microelectrodes were successfully applied to measure the concentration of Cl− and Na+ over corroding cut-edge samples of metallic coated steel and can be recommended for measuring the distribution of Na+ and Cl− in corrosion applications.