Structural evolution of co-deposited Zn–Cr coatings produced by vacuum evaporation

Zn and Cr were evaporated simultaneously using two e-beam guns to heat crucibles containing the pure metals. The metallic vapors generated are intermixed and pass through a specially designed aperture that assures homogeneous deposition at the surface of the steel substrate, which continuously advances. The source positions were adjusted to produce a coating with a chromium content which decreases from the substrate interface to the external surface. This article discusses the chemical and microstructural variations of these co-deposited layers as a function of chromium content. In order to improve the adhesion of these coatings on low carbon steel, the deposition chamber has been designed in such way as to produce a thin precoat (<200 nm) consisting of a ZnCr alloy with a high chromium concentration.