Self-cleaning coating for exterior walls of concrete buildings

Due to the advantages of beautiful appearance, exterior wall real stone paint with properties of low cost and good weather resistance has been widely applied on concrete buildings for aesthetics and protection. However, the hydrophilicity of exterior wall real stone paint makes it susceptible to pollution by dust, acid rain and so on. Superhydrophobic coatings with excellent self-cleaning properties may effectively alleviate these problems, but the fabrication of real stone paint coatings with superhydrophobicity has not been reported yet. Here, the authors developed a superhydrophobic exterior real stone paint (SEP) coating with a water contact angle of 154 ± 3° and a rolling angle of 13 ± 2° through a simple and highly efficient physical blending method using an emulsion, natural sand, low-surface-energy reagents and nano-silicon dioxide (nano-SiO₂). The SEP coating possessed excellent self-cleaning properties for pollutants, including soil, dust and rust water, and had good anticorrosion capability and outdoor time stability. The SEP coating also showed better solar reflectance characteristics than the normal exterior real stone paint coating, which may contribute to lowering of temperatures in buildings during hot weather and saving energy. Besides, a colorful SEP coating for decorative requirements and a large-area SEP coating for practical application could be effectively fabricated, which are expected to have promising application prospects.