Sea water is a widespread but aggressive medium that is often in contact with metallic structures, therefore, their protection against corrosion is needed. Carbon steel is one of the most commonly used structural materials because of good physical and chemical properties and low cost compared with other metallic materials with similar characteristics. The most effective corrosion protection is obtained by a combination of protective coatings and cathodic protection. Under conditions of intensive cathodic polarization it often comes to reduction in adhesion between the protective coating and metal substrate, that’s why it is important to examine and assess the integrity of such systems before application of coatings. Studies were conducted on five different systems of insulation coatings. Samples were exposed to intensive cathodic polarization in simulated sea water solution. To assess the integrity of the organic insulation system, cathodic disbondment test has been conducted. To test the coating protective properties and to get a better insight into the processes that take place on the analyzed samples, electrochemical impedance spectroscopy, as well as current and potential measurements have been conducted in time. Based on the results analysis it was concluded that two tests systems should not be applied in studied experimental conditions due to the weakening of adhesion and disbondment of coating from the steel structure. Bituminous coating can be applied for initially effective, but not long-term protection of steel. From electrochemical parameters it can be concluded that the corrosion rate is the fastest compared to other tested samples. In tested conditions, epoxy based coatings and highly elastic coating reinforced with glass fibres provide excellent results. If during transport, installation or application there is a possibility of mechanical damage, it is recommended to use the system with a reinforced coating because it has high mechanical strength on top of excellent corrosion protection. Finally, it can be concluded that with the combination of coatings and cathodic protection, effective and long-lasting corrosion protection can be achieved if a suitable insulation system is selected.