Benedetti Alessandro, Cirisano Francesca, Delucchi Marina, Faimali Marco, Ferrari Michele
Istituto per l'Energetica e le Interfasi - U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy.
Istituto per l'Energetica e le Interfasi - U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy.
Colloids Surf B Biointerfaces. 2016 Jan 1;137:167-75. doi: 10.1016/j.colsurfb.2015.07.045. Epub 2015 Jul 26.
Superhydrophobic coating technology is regarded as an attractive possibility for the protection of materials in a sea environment. DC techniques are a useful tool to characterize metals' behavior in seawater in the presence/absence of coatings and/or corrosion inhibitors. In this work, investigations concerning Al-5%Mg alloy with and without a sprayed superhydrophobic coating were carried out with potentiodynamic scans in photobiologically active and not active seawater (3 weeks of immersion). In not photobiologically active seawater, the presence of the superhydrophobic coating did not prevent pitting corrosion. With time, the coating underwent local exfoliations, but intact areas still preserved superhydrophobicity. In photobiologically active seawater, on samples without the superhydrophobic coating (controls) pitting was inhibited, probably due to the adsorption of organic compounds produced by the photobiological activity. After 3 weeks of immersion, the surface of the coating became hydrophilic due to diatom coverage. As suggested by intermediate observations, the surface below the diatom layer is suspected of having lost its superhydrophobicity due to early stages of biofouling processes (organic molecule adsorption and diatom attachment/gliding). Polarization curves also revealed that the metal below the coating underwent corrosion inhibiting phenomena as observed in controls, likely due to the permeation of organic molecules through the coating. Hence, the initial biofouling stages (days) occurring in photobiologically active seawater can both accelerate the loss of superhydrophobicity of coatings and promote corrosion inhibition on the underlying metal. Finally, time durability of superhydrophobic surfaces in real seawater still remains the main challenge for applications, where the early stages of immersion are demonstrated to be of crucial importance.
超疏水涂层技术被认为是保护海洋环境中材料的一种有吸引力的可能性。直流技术是表征有/无涂层和/或缓蚀剂时金属在海水中行为的有用工具。在这项工作中，通过在光生物活性和非光生物活性海水中进行动电位扫描（浸泡3周），对有和没有喷涂超疏水涂层的Al-5%Mg合金进行了研究。在非光生物活性海水中，超疏水涂层的存在并不能防止点蚀。随着时间的推移，涂层出现局部剥落，但完整区域仍保持超疏水性。在光生物活性海水中，没有超疏水涂层的样品（对照）的点蚀受到抑制，这可能是由于光生物活性产生的有机化合物的吸附。浸泡3周后，由于硅藻覆盖，涂层表面变得亲水。如中间观察结果所示，硅藻层下方的表面由于生物污损过程的早期阶段（有机分子吸附和硅藻附着/滑动）而可能失去了超疏水性。极化曲线还表明，涂层下方的金属经历了与对照中观察到的类似的缓蚀现象，这可能是由于有机分子透过涂层渗透所致。因此，在光生物活性海水中发生的初始生物污损阶段（数天）既能加速涂层超疏水性的丧失，又能促进底层金属的缓蚀。最后，超疏水表面在实际海水中的长期耐久性仍然是应用中的主要挑战，其中浸泡的早期阶段被证明至关重要。
