## 6 Conclusions  
The conclusion presented below can be derived from the tests conducted on reinforced concrete tanks and silos and from multi-aspect analyses of various factors which determine the effectiveness and reliability of results from corrosion testing performed on concrete cores drilled from the structure:  
* The traditional in-situ diagnostics testing of corrosion using the electrochemical methods (measurements of potential, resistivity, polarization) provide valuable information; however, they only indicate the temporary electrochemical state of the reinforced concrete structure, which depends on thermal and humidity conditions at the moment of measurements;
* Generally, diagnostics processes for reinforced concrete structure conducted on large areas of concrete, and/or at high altitudes, and/or in difficult-to-access areas are troublesome and dangerous. Hence, drilling cores with fragments of the secondary reinforcement (e.g., spacer bars, stirrups, binders) from the structure greatly improve safety and comfort of tests by conducting them in the laboratory conditions. There, polarization tests on corrosion rate of reinforcement, and tests on protective properties of concrete against reinforcing steel can be performed as well;
* The extreme values of corrosion current density can be determined when extreme thermal and humidity parameters are set in the climate chamber while testing the rate of corrosion current for reinforcement in the tested cores. Selection of temperature and relative humidity in the climate chamber should be based on the analysis of historical weather and operational data from a few years, concerning the location of the tested civil structure. The set of values of corrosion current density obtained in that way, after conversion into corrosion rate values, can be included in the mechanical models representing degradation of the tested reinforced concrete structures, which provides more precise estimation of the remaining service life of this structure;
* The arrangement of the three-electrode system on the drilled concrete cores should minimize the measuring errors. Therefore, the counter electrode in the form of conductive coating applied on the side wall of the cylindrical core with the painting technique is the novelty proposed by the authors. The main advantage of this solution is the constant electric contact between the coating and the core concrete, which does not require any additional conductive medium that changes electric properties of concrete. The second improvement of the three-electrode system consists in using the solid reference electrode embedded in cement grout in the opening with bottom placed very close the working electrode. This solution minimizes the problem related to resistance compensation and increases stability of the results while polarization curves are recorded during the tests on corrosion rate. Moreover, cores with fragments of rebars which are used as working electrodes in the three-electrode system, drilled from the structure cause that the polarization surface area can be precisely determined by directly measuring side walls of rebars after crushing the cores at the end of the corrosion tests;
* The described examples of corrosion tests performed on reinforced concrete tanks for fresh water and silos for cement storage confirmed the application possibilities of the diagnostics method based on the tests on drilled cores and improved by the authors. At satisfactory protective properties of concrete against reinforcement, changes in thermal and humidity parameters in the tanks did not produce any significant differences in corrosion rate, which was generally kept at low level. The results were different for the silos, where concrete carbonation decreased protective properties of concrete. Consequently, values of corrosion current density were high under conditions favourable for corrosion.