Surface plasmon resonance spectroscopy is a technique used for detection of subtle changes in the optical properties of materials and finds wide application in biosensors and chemical tranducers. Due to the extreme sensitivity, contamination of the sensor surface is a major problem in experiments involving surface plasmon resonance measurements. We report here that aluminum oxide (alumina) can be used as a perfect protective coating for the metal in surface plasmon resonance experiments. The alumina is electron beam evaporated to create a relatively thick layer on the sensor (gold) surface, immediately after the gold deposition process without exposing the latter to environmental conditions. During experiment, this protective coating was removed by dissolving the alumina in an alkaline solution, thus exposing the uncontaminated gold surface for further experiments. By the study of the shift in the waveguide modes supported in the dielectric alumina layer, the dissolution of alumina was monitored. Theoretical simulation studies using Fresnel's equations were done to explain the dissolution plots obtained. Atomic force microscopy of the alumina surface provided information on the variation of the roughness parameter, with the progress in dissolution. It was found that the roughness of the surface at all points during the dissolution process remained much below the wavelength of the incident radiation, thus justifying the modeling of the system as stacked Fresnel's layers.