Influence of silica nanoparticles added to an organosilane film on carbon steel electrochemical and tribological behaviour

The electrochemical behaviour and tribological properties of carbon steel coated with bis-[trimethoxysilylpropyl]amine (BTSPA) filled with SiO2 were evaluated. The silane film filled with SiO2 was prepared by adding different SiO2 concentrations. The electrochemical behaviour of the coated steel was mainly evaluated by means of open-circuit potential (EOC), electrochemical impedance spectroscopy (EIS) and polarization curves, in 0.1 mol L−1 NaCl solution. Structural and morphological characterizations were made by optical, electron and atomic force microscopy (AFM). EOC and EIS data showed that sample filled with 300 ppm SiO2 presented the highest EOC and total impedance value. AFM measurements showed a homogeneous particle distribution of SiO2 particles. Nanohardness measurements showed SiO2 promoted an increase of the hardness mean value (1.70 ± 0.11 GPa to non-filled BTSPA and 2.21 ± 0.05 GPa for sample filled with 300 ppm SiO2). Silane films when filled with SiO2 particles improved the corrosion resistance of the steel substrate. The optimum SiO2 particles concentration in silane solution is 300 ppm SiO2. Incorporation of an extra amount of silica into BTSPA film led to degradation of the corrosion protection of the film to the substrate.