Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Amorphous carbon (a-C) and several related materials (DLCs) may have ultralow friction coefficients that can be used for saving-energy applications. However, poor chemical bonding of a-C/DLC films on metallic alloys is expected, due to the stability of carbon-carbon bond's. Silicon-based intermediate layers are employed to enhance the adherence of a-C:H films on ferrous alloys, although the role of such buffer layers is not yet fully understood in chemical terms. The chemical bonding of a-C:H thin films on ferrous alloy intermediated by a nanometric SiCx:H buffer layer was analyzed by X-ray photoelectron spectroscopy (XPS): The chemical profile was inspected by glow discharge optical emission spectroscopy (GDOES), and the chemical structure was evaluated by Raman and Fourier transform infrared spectroscopy techniques. The nature of adhesion is discussed by analyzing the chemical bonding at the interfaces of the a-C:H/SiCx:H/ferrous alloy sandwich structure. The adhesion phenomenon is ascribed to specifically chemical bonding character at the buffer layer. Whereas carbon carbon (C-C) and carbon silicon (C-Si) bonds are formed at the outermost interface, the innermost interface is constituted mainly by silicon iron (Si-Fe) bonds. The oxygen presence degrades the adhesion up to totally delaminate the a-C:H thin films. The SiCx:H deposition temperature determines the type of chemical bonding and the amount of oxygen contained in the buffer layer.729 1590915917UCSINCT-INES [554336/2010-3]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)PETROBRAS [504062/2014-0]FAPERGSFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)SUMA2 Network ProjectEuropean Commission (IRSES Project) [318903]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)