Effect of Surface Roughness, Contact Angle, and Temperature on Salt Crystallization from Sessile Drops

This study investigated the influence of salt solution drying temperature, substrate material, and surface roughness on deposit morphology and deposition pattern. Sessile drop drying experiments were conducted at 20 °C, 70 °C, and 200 °C using synthetic seawater and individual salt solutions on aluminum, sapphire, and polished and rough yttria-stabilized zirconia (YSZ). The results demonstrate that smooth surfaces, such as sapphire and polished YSZ, facilitate the crystallization of large, deposits with limited deposit spread. Conversely, rougher surfaces enhance heterogeneous nucleation earlier in the drying process, resulting in a broader distribution of fine crystals. However, rough but hydrophobic surfaces showed coalescence of precipitates, emphasizing the effect of hydrophobicity. Additionally, the results showed that higher temperatures lead to edge-dominant deposition while lower temperatures promote more uniform salt distribution. These findings provide insights into the interplay between substrate properties, drying conditions, and salt deposition behavior. The results are discussed in the context of fouling behavior relevant to marine turbine compressors and offer a foundation for designing fouling-resistant materials to minimize the maintenance efforts, enhance the long-term efficiency and reliability of systems exposed to seawater environments.