Chemical structure and morphology of ultrathin combustion CVD layers on zinc coated steel

Combustion chemical vapor deposition (CCVD) as an atmospheric process offers an environmental friendly alternative to conventional surface treatments for reactive metals. Ultrathin nanoscaled silica like layers can be deposited on various metallic substrates. The here presented results focus on the deposition of thin SiO2-layers on zinc coated steel as an interface layer between an organic coating and the metal substrate. Infrared reflection absorption spectroscopy (FT-IRRAS) and X-ray photoelectron spectroscopy were used to reveal the chemical structure of the films. While no residual carbon was detectable the SiO2-film contains free surface hydroxyl groups. The characteristic sub-microscopic features and the initial growth of the layer are characterized by means of field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The increasing coverage of the surface on a technical galvanized steel surface was followed by means of AFM as well as by cyclic voltammetry. The latter surface electrochemical technique allowed to quantify the residual free surface area. It could be shown that 99% coverage can be achieved in less than 1 s deposition time.