Effect of off-time on the composition of pulse-plated Cu-Ni alloys

The limit of applicability of a previously developed mathematical model for the prediction of pulse-plated Cu-Ni alloys in the presence of a mass-transport controlled corrosion reaction has been investigated. The growth of a Cu-rich layer on the alloy surface, which suppresses further dissolution of nickel, has been theoretically analyzed. This model is used to compute t_cr, the maximum value of off-time when nickel dissolution is governed by a mass-transfer-controlled Cu²⁺ deposition reaction. Experimentally, a shift in alloy composition from the corrosion model is observed at long pulse-off times. The measured values of off-time where alloy compositions deviate from corrosion behavior concurs with the theoretically computed t_cr value.