Diagnostics of existing buildings includes, among others research to assess their durability. In the case of reinforced concrete structures, such tests include semi-destructive electrochemical tests to forecast the corrosion risk of steel bars in concrete, and one of the methods used is the electrochemical, polarizing galvanostatic pulse method. The aim of the article was to recognize the influence of element effort on the measurement results obtained with this method. For the tests, a reinforced concrete cantilever slab loaded monotonically was used. During the tests, the stationary potential and corrosion current density of the main reinforcement bars, as well as the resistivity of the concrete cover, were measured. Based on the results obtained, it was found that the level of effort on the element affects the values of the measurements performed. Differences in the values of measured parameters at different levels of element effort are sometimes so large that they may significantly affect the conclusions about the corrosion risk of the tested reinforcement, and thus incorrectly estimate the durability of the tested element.