Thermodynamics of Adsorption of Brighteners on Polarized Nickel from Watts Bath Solution

Abstract

The adsorption of coumarin, nitrocoumarin, and p‐toluene sulfonamide on nickel from Watts bath solution has been studied using a polarization technique. The exchange current densities with and without additives were evaluated using a Tafel relation. The addition agents inhibited the deposition process. Surface coverages calculated from the values were fit into the Langmuir adsorption isotherm. Thermodynamic parameters (, , and ) for the adsorption of the addition agents have been evaluated using the Bockris‐Swinkles adsorption isotherm. The values of are negative indicating the strong interaction and reactive inhibition of the deposition process by these additives. The electrodeposition interaction is discussed from the viewpoint of the adsorption of the additive molecules on the metal solution interface.