Corrosion mitigation of metals and alloys via superhydrophobic coatings with plasma surface and heat treatment processes

Abstract

Many industries utilize metals and alloys because of their exceptional properties, including high strength, conductivity, load-bearing capability, ductility, creep, and fatigue resistance. Among the metals and alloys, aluminum and its alloys are mostly subject to corrosion when encountering under severely adverse conditions that result in oxidation, failure of metallurgic luster, modifications in the sizes, strength, and changes in other physical and chemical properties. In this study, we produce superhydrophobic coated (SHC) aluminum 2024 alloy (AA2024) substrates for corrosion mitigation using a combination of physical and chemical modification processes. Plasma surface and heat treatment have been utilized for physical modification by forming nano-scaled roughness on the AA2024 substrates. To improve the surface hydrophobicity, chemical modification was achieved using low surface energy coatings. The corrosion behavior of plasma surface and heat-treated superhydrophobic coated (PSH-SHC) AA2024 substrates were evaluated by immersing into a 3.0% sodium chloride (NaCl) solution. The domination of plasma surface and heat treatment on the surface roughness, wettability, and corrosion resistance of the prepared AA2024 substrates was examined by applying water contact angle (WCA) measurements, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and salt soaking tests. The test results confirm that the PSH-SHC AA2024 substrates remain superhydrophobic with a WCA ≤ 168° for an extended period of time with superior corrosion resistance in harsh environments. The WCA measurements slowly reduced from 168° to 157° after immersion in the 3.0% NaCl solution for 30 days. It demonstrates that the plasma surface and heat treatment mechanisms drastically enhanced the adhesive strength between the AA2024 substrate and the superhydrophobic coatings. The PDP and EIS results also showed that the corrosion rates of the 8H-PSH-SHC AA2024 substrate were undesirably low and raised with expending immersion time in the 3.0% NaCl solution. It is concluded that techniques applied in this study are found to be promising and critically important for a longer service time of the metals and alloys for broader industrial applications to mitigate the corrosion problems.