Abstract
Cracks are often formed in nickel-alloy plating by high tensile stress. Therefore, an accurate crack detection method is required. The method for detecting cracks in Ni-W plating film with electrochemical impedance spectroscopy (EIS) was studied in the present paper. The impedance of Ni-W plating film without cracks in 1M sulfuric acid solution shows two capacitive loops. The impedance of Ni-W plating film with cracks in 1M sulfuric acid solution shows also two capacitive loops. The capacitive loops of impedance of Ni-W plating film without crack were smaller than those of Ni-W plating film with cracks. Curve-fitting was performed for the impedance spectra by assuming equivalent circuits, and the calculated impedance spectra were in agreement with the experimental results. In those results, the charge transfer resistance and double-layer capacitance varied with the area of cracks in Ni-W plating film. It can be concluded that impedance analysis can detect cracks in Ni-W plating film.
