J. Electroanal. Chem., 86 (1978) 233--239 233 © Elsevier Sequoia S.A., Lausanne -- Printed in The Netherlands Preliminary note ELECTROCRYSTALLIZATION NOISE: A PHENOMENOLOGICAL MODEL C. GABRIELLI, M. KSOURI and R. WIART Groupe de Recherche no.4 du C.N.R.S. :"Physique des Liquides et Electrochimie'; associ} l'UniversitJ Pierre et Marie Curie, 4 place Jussieu, 75230 Paris Cedex 05 (France) (Received 5th October 1977) It is known that the electrocrystallization noise can be connected with the structural organization of electrodeposits [1, 2]. In the case of zinc electro- deposition which can lead to spongy, compact or dendritic deposits, the experimental study of the fluctuations of the electrolysis current allows us to establish some close correlations between the deposit morphology and the noise power measured in a low frequency range. As for nickel deposits which are compact with various preferred orientations, the noise power has been shown to be proportional to the electrolysis current I raised to the power a whose value depends on the orientation: a is close to 2 for the [110] orienta- tion instead of 1 approximately for the [211] orientation. The purpose of this paper is to propose a phenomenological model which partly explains these correlations between the noise power and the structural organization of electrodeposits. At the metal-electrolyte interface, the total current I which flows through the electrode can be written as I = ffJdS (1) where J is the c.d. (current density) passing through an elementary area dS. Let us assume that I = (/) + i where (I) is the average value of the current I, • and i denotes the fluctuations corresponding to the electrocrystallization noise. Two cases can be considered, related to fluctuations i arising from either Jot S. In the first case, we will study the fluctuations i arising from the fluctuations of the interfacial reaction rates; in the second one, we will take account of the area variations due to the random birth-and-death processes of the crystallites on the surface. In any case, the fluctuations i will be characterized by the autocorrela- tion function ~/ii(r) = (i(t)i(t + r)) (2)