Multifunctional Dark-Colored Coating for Roof Renovation: Combining Corrosion Protection and Heat Reduction in a Single Application

In response to the growing challenges of global warming, one of the key phenomena affecting thermal comfort and energy efficiency in cities is the Urban Heat Island (UHI) effect. This refers to higher temperatures in urban areas compared to rural surroundings, caused by building materials like concrete and asphalt that absorb and store heat. In cities with dense buildings and limited green space, there is increased demand for air conditioning, leading to higher energy costs and greater air pollution. Mitigating the UHI effect is thus essential for sustainable urban development.

Roof surfaces, highly exposed to solar radiation, are among the main contributors to heat accumulation. Applying appropriate thermal insulation coatings can significantly improve building energy efficiency. Developing coatings with high Total Solar Reflectance (TSR) can reduce roof temperatures and decrease air conditioning demand, addressing rising energy costs and climate change.

This study aimed to develop dark-colored, multifunctional roof coatings combining corrosion resistance and heat-reduction properties. Direct-to-metal (DTM) coatings, which eliminate the need for an anti-corrosion primer, simplify application and reduce painting time. These formulations incorporated near-infrared (NIR) reflective inorganic pigments that reflect solar radiation in the NIR spectrum, improving thermal performance.

The coatings underwent extensive testing, including adhesion, impact resistance, flexibility, and accelerated aging in salt spray, humidity, and UV chambers. Optical and thermal properties were assessed with UV/VIS/NIR spectrophotometry, and emittance was measured with Total Hemispherical Emittance Measurements.

The coatings demonstrated excellent adhesion and corrosion resistance, with heat-reflective NIR pigments reducing substrate temperature even in dark-gray colors. These results highlight the coatings' effectiveness in mitigating the UHI effect and improving building energy efficiency.

Acknowledgments
This work was financially supported by the Łukasiewicz Research Network Centre (Poland) – grant number: 1/Ł-IMPiB/CŁ/2021