A Comparative Study on the Corrosion Resistance and Long-Term Stability of Hierarchical Superhydrophobic Nickel Coatings Obtained by One-Step and Two-Step Electrodeposition Processes

Hierarchically structured nickel coating is a special type of coating with both micro- and nano-scale features, which give rise to its superhydrophobic properties. This study compares these coatings obtained via two electroplating methods, one-step and two-step processes. The one-step method, utilizing an organic bath, achieves hierarchical structure formation and surface energy reduction simultaneously, without requiring a 2-week air storage post-electrodeposition. Water contact angles of 155.7 +/- 0.3 and 172.3 +/- 0.2 degrees were observed for the two-step and one-step coatings, respectively. Electrochemical analyses reveal a 50% reduction in corrosion current density and a threefold increase in charge transfer resistance for the one-step coating, indicating superior corrosion performance compared to the two-step coating. Long-term durability studies under saline conditions demonstrated the one-step coating is superior in maintaining hydrophobicity and corrosion resistance over extended immersion periods. Notably, the one-step coating exhibits sustained performance, maintaining a Wenzel (petal) state and higher charge transfer resistance (approximate to 10 k ohm cm2) even after 9 days of immersion, while the two-step coating experiences substrate penetration by saline solution.