Degradation mechanisms of corrosion and biofouling resistance of superhydrophobic coatings in harsh marine conditions

• Published in: Progress in organic coatings Vol. 173; p. 107222
• Main Authors: Cao, Xiangkang, Pan, Jinglong, Cai, Guangyi, Hu, Yunfei, Zhang, Xinxin, Dong, Zehua
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.12.2022; Elsevier BV
• Subjects: Abrasion; Air bubbles; Biofouling; Coating; Coatings; Corrosion; Corrosion prevention; Corrosion resistance; Cushions; Degradation; Depletion; Failure mechanisms; Hard surfacing; Hydrophobic surfaces; Hydrophobicity; Oxidation; Salt spray tests; Superhydrophobicity; Surface energy; Water erosion; Wettability; Coating; Corrosion; Superhydrophobicity; Biofouling; Failure mechanisms
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2022.107222

The easy loss of non-wettability of superhydrophobic coatings (SHPs) severely hinders their applications in practice, and an understanding of their degradation mechanism would be helpful to solve this problem. In this work, we studied the degradation process of superhydrophobicity of SHPs subjected to static salt spray and dynamic abrasion tests, and found that most SHPs feature a considerable anti-corrosion and anti-biofouling ability in the initial period. Unfortunately, with prolonged aging tests, the air cushion on the surface of SHPs is depleted due to static saline corrosion and/or dynamic erosion. Morphological and chemical observations suggest that there are two mechanisms to explain the static and dynamic degradation of SHPs, respectively. First, due to the chemical or photo-oxidation of coatings, the SHPs become more hydrophilic and prone to capture hygroscopic salt particles instead of air bubbles during salt spray tests, leading to the depletion of air cushion. Second, the micro-nano rough structures of SHPs may be polished away due to solid particle abrasion or flowing water erosion, causing non-wettability loss. Therefore, to sustain a reliable superhydrophobic surface, it is necessary to armor the micro-nano structures with a hard coating or shell. Finally, a mathematical model was proposed to explain the non-wettability of SHPs based on their roughness and surface energy. We studied the failure mechanisms of three kinds of superhydrophobic coatings when subject to cyclical salt spraying-drying tests and abrasion erosion tests. The non-wettability of SHC samples endows themself with remarkable anti-corrosion and bio-fouling resistance. However, the non-wettability may deteriorate due to the depletion of air cushion or topcoat caused by abrasion and erosion, thus leading to failure for both anti-corrosion and anti-biofouling abilities. [Display omitted] •Corrosion and biofouling repellency depend on superhydrophobicity of coatings.•Abrasion test hurts superhydrophobic coatings more than static salt spraying test.•Non-wettability loss of coating is subject to two-stage deterioration mechanism.•A math model is proposed to calculate non-wettability on roughness and surface energy.