The molybdate–zinc conversion process was investigated by means of different techniques such as EIS, interfacial pH measurements, QCM and SECM. SEM and XPS complemented the electrochemical measurements. EIS results have shown different behaviour as function of the pH of the solution. Interfacial pH measurements have evidenced that the coatings were formed after about 200 s. The QCM measurements have exhibited three main characteristic regions and have shown that the formation kinetics was pH-dependent. The surface characterization has shown the presence of Mo5+ inside the coatings. The Mo and P amounts did not markedly change when the conversion time was increased.