Electrodeposition of black chromium thin films from trivalent chromium-ionic liquid solution

In the present study, black chromium thin films were electrodeposited from a solution of 1-butyl-3- methylimidazolium tetrafluoroborate ([BMIm][BF4] ionic liquid containing trivalent chromium (Cr(III)). Homogeneous and well adherent coatings have been obtained on nickel, copper and stainless steel substrates. The nucleation and growth of the films were investigated by cyclic voltammetry and current-density/time transient techniques. SEM/EDS, XPS and XRD were used to study the morphology, chemical composition and structure of the films. The coatings consist of a mixture of metallic chromium and chromium oxides (black chromium) and present a sub-micrometric granular structure