Scanning micropipette contact method (SMCM) suffers from the droplet evaporation and crystallization which limits the use of most saline electrolyte solutions under natural air humidity. We advanced this technique by scanning the droplet under mineral oil that was placed on the surface of substrate, which significantly improved the stability of droplet. This allowed for the use of 3.5 wt% NaCl solution to map the localized corrosion of AA7075-T73 aluminum alloy regardless of ambient humidity levels. Maps of corrosion potentials and corrosion currents extracted from potentiodynamic polarization curves showed good correlations with the surface features. We also optimized the long-term oil-immersed SMCM scanning by eliminating the Ag+ contamination that was released by the commonly used non-isolated Ag/AgCl quasi-reference counter electrode (QRCE). Ag+ ions were reduced at the alloy surface when they diffused to the droplet, generating unwanted cathodic current, causing the corrosion potential to shift in the positive direction over time. This work demonstrates the viability of the oil-immersed SMCM and opens up the avenue to mechanistic corrosion investigations at the microscale level using aqueous solutions that are prone to evaporation under noncontrolled humidity levels.