The functionalization of carbon electrodes with aryl films can be achieved via the electrochemical reduction of the corresponding diazonium salt. We have previously shown that this deposition procedure will produce multilayer films on ordered graphite under certain conditions. We examine here the formation of multilayer films on glassy carbon (GC) electrodes by potential step electrolysis of diazonium salts for longer periods of time. The deposition of diethylaniline (DEA) is tracked with the use of infrared reflectance absorption spectroscopy and scanning force microscopy. DEA is continually deposited over a 30 min potential step and the film thickness approaches 20 nm. Phenylacetic acid and nitrophenyl films that are 15-25 nm thick can also be deposited in this way. We also find that, despite the presence of a relatively thick DEA film on a GC electrode, electron transfer to benchmark redox systems is not completely blocked. We attribute the compromised blocking to a high density of defects in the film structure.