A square-wave potential anodizing procedure to obtain noble metal surfaces with both a controlled roughness and a reproducible electrochemical response is presented. The influence of the characteristics of the square-wave potential perturbation are systematically studied. The modification of the surface takes place through the formation of a hydrated platinum oxide layer which is later electroreduced. The mechanism of growth of the hydrated oxide layer under both square-wave potential perturbation and potentiostatic conditions is critically discussed in terms of a complex sandwich-type structure.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA)Facultad de Ciencias Exactas