METHOD FOR SELECTIVE PHOSPHATING OF COMBINED METAL STRUCTURE Russian patent published in 2022 - IPC C23C22/73 C23C22/36 C23C22/34 C23C22/40 C23C22/44 C23C22/80 C23C22/83 

FIELD: metallurgy.

SUBSTANCE: group of inventions relates to a method for preliminary chemical treatment and selective phosphating of a combined metal structure containing at least one part made of aluminum, and at least one part made of zinc, and, optionally, an additional part made of iron, to a composition for selective zinc phosphating, a concentrate for its production, and to the use of a combined metal structure phosphated by the mentioned method. At the first stage of the method, the structure is treated with an aqueous composition for zinc phosphating with the formation of a layer of crystalline zinc phosphate, covering the surface, having a covering density in the range from 0.5 to 5 g/m² on parts made of iron and zinc, and at the same time without formation of a layer of zinc phosphate, having a covering density of less than 0.5 g/m² on aluminum parts. At the second stage, an aqueous acidic passivating composition is applied to the structure.

EFFECT: reduction in precipitation of cryolite on a surface of metal components, in particular on aluminum surfaces.

14 cl, 3 tbl