The anticorrosion performance of the silicone-epoxy coatings on 2024 Al-alloy with different surface pretreatments were systematically evaluated in 3.5 wt.％ NaCl solution by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electrochemical microscopy (SCEM), poll-off test and ultra-depth three-dimensional microscope (UTM). Based on hypothetical corrosion mechanism, electrical equivalent circuits (EECs) were developed and simulated to correspond to the experimental EIS data. The cross section and morphology of the Al-alloy subjected to different pretreatments and the coatings were characterized using UTM. The delaminated area and the roughness of the interfaces were discussed from their respective break-point frequency and fractal dimensions deduced from EIS data. The SCEM redox competition mode, in which smaller tip current reflects severer corrosion reaction at the defect, was used to monitor the local corrosion behavior of the Al-alloy substrate under the scribe. The average adhesion of the coatings on the samples were evaluated using pull-off adhesion tests before and after immersion in a NaCl solution. Based on the above test results, a specific alkaline pretreatment of the Al-alloy prior to the coating has been found to improve the corrosion resistance of the Al-alloy.