Polymer-infiltration-pyrolysis (PIP) inspired hydrophobic nano-coatings for improved corrosion resistance

Nature-inspired hydrophobic coatings have caught great attention due to their repellency to corrosive mediums and less interaction between substrate and chemical species. Aluminum is considered one of the metals having superior properties against corrosion due to passive film formation. It can further be enhanced by the formation of a hierarchical structure through 2nd step anodization. In previous studies, carbon infiltrated in anodized alumina pores through CVD method (chemical vapor deposition) was quite an expensive and complex method. The fabrication of anti-corrosion coating with a simple and cost-effective method will broaden the aluminum alloy applications in the chemical, petrochemical, and aerospace industries, etc. In this research, pyrolytic carbon is infiltrated in porous alumina through pyrolysis at three different temperatures for 30 min under a controlled environment by using flaxseed oil as a source of carbon. The surface morphology along with chemical composition and wetting angle were studied through SEM (Scanning Electron Microscope), EDX (Energy Dispersive X-ray Spectroscopy), and Sessile drop method. It was found that both low surface energy and high roughness participate in increasing the wetting angle. Nanocomposite coating having maximum carbon content has a maximum wetting angle with inorganic liquid. Based on the electrochemical behavior determined by Tafel and EIS (Electrochemical Impedance Spectroscopy) analysis, the hydrophobic coating containing 57.5% carbon content having a contact angle of 95^° exhibits maximum corrosion resistance of around 28,000 kohm as compared to anodized aluminum having minimum corrosion resistance of around 4.26 kohm. The results and the cost-effective method could be beneficial in aircraft parts as well as in aeronautical applications.