Theoretical calculations for the work of formation of two-dimensional nuclei, Wm,, of the h.c.p. lattice are presented. The dependence of Was on supersaturation is given graphically. The calculations have been proved in the case of cobalt electrodeposition. The polarization curves in the deposition of cobalt from pure solutions of cobalt sulphate with the addition of 5,lO and 20 811 H,BO, have been studied at 15, 20, 30,40, 60 and 80ยฐC and pH 5. At high temperatures and low current densities, cobalt is deposited with low overvoltage and the orientation is along the [OOOl] axis. Orientations along the axes [ll?O] and [lOTO] [1120] are obtained when cobalt is deposited with medium overvoltage and at low temperatures: texture along the [lOTO] axis is developed. at high current densities and high overvoltage, a The addition of HsBOa leads to an increase of overvoltage, which results in a change of the orientation axis. Thus with a content of 10 g/l H,BO, it is not possible to obtain a texture along [OOOl] under any conditions, while with 20 g/l H,BO,, besides the absence of [OOOl], no pure orientation can be obtained along [1120]. with the two-dimensional theory of preferred orientation. The experiments are in general agreement RQsum&-Calcul theorique du travail de formation W til de germes bidimensionnels d'un r&au hexagonal analogue a celui du cobalt &ctrodepose et mise en evidence graphique de sa dependance sur la sursaturation. Etablissement experimental a 15, 20, 30,40, 60, 80ยฐC et pH 5 des courbes de polarisation de 1'6l&rodbposition du cobalt a partir de solutions de COS04 addition&es de 5,lO et 20 g/l de HsBO,. A haute temperature et basse densite de courant, Co se depose avec faible surtension, en s'orientant selon I'axe [OOOl]. Les orientations selon les axes IllZO], [lOTO], [llZO] s'observent, avec des surtensions moyennes, aux temperatures peu blew%; sous forte densite de courant et forte surtension, la texture se developpe selon l'axe [lOTO]. L'addition de H3B08 accroit la surtension et change en consequence l'axe d'orientation. Ainsi, avec 10 g/l HIBOI, il n'est plus possible d'obtenir la texture selon l'axe [OOOl] quelles que soient les condition et avec 20 g/l H,BOII, en outre, aucune orientation privil+$e ne se manifeste selon l'axe [IlZO]. Ces experiences sont en accord general avec la theorie bidimensionnelle de l'orientation preferentielle.