The task of this paper was to test the protective properties ofcommercial polyisobutylene-based viscoelastic coating applied to the steel surface. The method used for testing is electrochemical impedance spectroscopy, using the ReCorr® QCQ device. In addition to easy application and environmental acceptability of the coating, impedance tests performed on undamaged sample indicate excellent protective properties of the coating. In order to examine the protective properties of the coating under non-ideal conditions, the sample was mechanically damaged, and impedance results showed that the coating on undamaged parts still provides excellent protection against corrosion. Furthermore, impedance measurements were performed on a mechanically damaged sample that was previously exposed to conditions of 100 % humidity and on a sample that was exposed to a 3,5 % NaCl solution. Test results indicated that the coating has poor protective properties in the presence of mechanical damage that penetrates to the steel surface, but shows excellent protective properties in the presence of mechanical damage that does not penetrate to the steel surface. Also it was necessary to determine the water uptake of the coating using the results of impedance measurements after exposing the sample to humid and salt conditions, and to compare the obtained results with the results from the literature. It is evident from the results that the coating shows higher water uptake when exposed to humid conditions than when exposed to salt conditions. The application of the EIS method using the ReCorr® QCQ device proved to be a simple and practical method for testing the protective properties of the viscoelastic coating. It also enables confirmation of the importance of environmental conditions and the type of damage for the protective properties of the coating.