Corrosion rate determination is often based on linear polarization (LPR) technique, carried out on small specimens in a controlled environment. The current is measured when the specimen is polarized away from its corrosion potential and the corrosion current gives the corrosion rate using Faraday's law. An important parameter in this calculation is the specimen area exposed. When testing rough, porous specimens such as thermally sprayed aluminum (TSA), the geometrical surface area does not represent the real surface area and hence the corrosion rate is not the actual corrosion rate. To measure the actual corrosion rate aluminum was thermally sprayed onto glass and the surface was characterized using a confocal microscope. These specimens were exposed to seawater at 25, 50 and 100°C, and the linear polarization resistance was determined using a potentiostat at room temperature. This was converted to a corrosion rate based on geometric and the actual surface area.