Caractérisation de revêtements électrodéposés de zinc-nickel

Characterization of Zn-Ni electrodeposited coatings

¹ Aérospatiale, Centre Commun de Recherches Louis Blériot, Suresnes
² INSA Lyon, Physicochimie Industrielle, Villeurbanne

Abstract

The composition, the structure, the morphology and the internal stress of ZnNi coatings electrodeposited on low allied steels were studied depending on the process parameters : nature of the electrolyte, current density, de-embrittlement treatment, and chromated passivation.

The studied alkaline process permits to obtain, according to the current density, a binary alloy, ranging from 6 to 10% of nickel. The morphology of the coatings is not affected by the de-embrittlement treatment. The studied acid process permits to obtain, according to the current density, an alloy which can be binary, ranging from 10 to 20% of nickel. The de-embrittlement treatment leads to create cracks through the coatings.

Compared to the alkaline process, the acid process seems to be more affected by the variation of the current density.

These results pointed out the possible problems of treated complex parts due to the notable variations of nickel content, crystal- lographical structures which can affect the protective properties of the ZnNi coating in corrosive environments.