title: Potentiodynamic study of Al-Mg alloy with superhydrophobic coating in photobiologically active/not active natural seawater.
abstract: 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.
authors: Istituto per l'Energetica e le Interfasi - U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy. Electronic address: alessandro.benedetti@cnr.it.
authors: Alessandro
authors: A
authors: Benedetti
authors: Istituto per l'Energetica e le Interfasi - U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy.
authors: Francesca
authors: F
authors: Cirisano
authors: Dipartimento di Ingegneria Civile, Chimica e Ambientale, P.le Kennedy,1, 16129 Genova, Italy.
authors: Marina
authors: M
authors: Delucchi
authors: Istituto per le Scienze Marine - U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy.
authors: Marco
authors: M
authors: Faimali
authors: Istituto per l'Energetica e le Interfasi - U.O.S. Genova, Consiglio Nazionale delle Ricerche, Via De Marini 6, 16149 Genova, Italy. Electronic address: mferrari@ge.ieni.cnr.it.
authors: Michele
authors: M
authors: Ferrari
mesh_terms: D000497:Alloys / Q000737:chemistry*; D000535:Aluminum / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008274:Magnesium / Q000737:chemistry*; D012623:Seawater
chemical_list: D000497:Alloys; D000535:Aluminum; D008274:Magnesium
keywords: Aluminum; Corrosion; Seawater; Superhydrophobic surface