Corrosion inhibitors are part of minimally intrusive repair and protection of historic buildings.

Saint Donatus, a symbol of the city of Zadar, is classified among the most famous and most valuable monuments in Croatia. Moreover, due to its unusual cylindrical appearance and robust monumentality, it belongs to the most significant European pre-Romanesque churches. The church is a protected cultural heritage listed in the Register of the Republic of Croatia on UNESCO’s list.

Today, as a result of numerous factors, the church needs urgent rehabilitation. After analyses of 3D scanning, it was determined that the biggest issue is the walls of the church and the construction itself, along with the roof. During the period 1927-1930, the stability of the foundation was compromised and reinforced concrete support construction was implemented under the roof from the south side, connecting the outer and inner rings of the church. The moisture penetrating into the medieval monument, in combination with sea dust, seriously endangers the reinforced-concrete structure that holds the church of St. Donat.

Last year, a repair project was initiated and Cortec’s MCI 2020 inhibitor was specified as coating to protect the support structure against corrosion. MCI 2020 is a surface-applied corrosion inhibitor designed to migrate through even the densest concrete structures and seek out the steel reinforcement bars in concrete. Even when not in direct contact with metal, the product will migrate through concrete to provide full protection. This environmentally safe inhibitor stops further corrosion of reinforcing metals, significantly extending the service life of the structure.

The famous Zagreb Cathedral is the tallest and one of the most valuable buildings in Croatia, attracting tourists from around the world. As the most impressive gothic-style sacral building southeast of the Alps, it is characterized by great architectural and historical value. Its construction dates back to 1093 and enriching of the cathedral continued by famous architects during the following centuries.

Since low-quality stone was used in the past due to economic reasons, it soon started to deteriorate, affected by weather and city pollution. A Committee for Reconstruction of the Cathedral was founded and selected Cortec for reconstruction of its famous towers.

During reconstruction work on the south tower, damaged steel bands were detected surrounding the tower approximately every 3 meters in height. They were covered with rust and in drainage areas. Visual damage to the diameter of the bands was present.

An economical approach with minimal intrusion to the structure was required to fix the bands’ condition. The mechanical resistance and structural stability of the tower needed to be maintained or improved. Following examination of the bands and experiments on the steel bars, experts recommended removing loose corrosion from the bands’ surfaces, enhancing the bands in damaged areas, and applying Cortec’s anticorrosion protection product, CorrVerter.

This water-based primer converts rust into a protective layer and is capable of penetrating into the depths of corroded surfaces. It contains a chemical chelating agent that modifies surface rust into a hydrophobic passive layer. Two-layers of CorrVerter coating were brushed onto smaller surfaces and sprayed in larger areas directly onto the metal bands. The bands were then reinforced with steel fishplates that were welded on the bands and also protected with CorrVerter.

With the help of a skilled team and good project management, the entire project was completed successfully with minimal cost or intrusion as specified. CorrVerter coating penetrated to the non-corroded part of the metal and stopped further advancement of the corrosion process.

Information provided by Cortec Corporation (