Non-Wettable Galvanic Coatings for Metal Protection: Insights from Nature-Inspired Solutions

Abstract

Natural surfaces, such as lotus leaves, springtail cuticles, and pitcher plant peristomes, exhibit extraordinary wetting behaviors due to their unique surface topographies and chemical compositions. These natural architectures have inspired the development of wettability models and the production of artificial surfaces with tailored wettability for advanced applications. Electrodeposited metallic coatings can imitate the wettability behaviors of natural surfaces, showing superhydrophobic, superoleophobic, or slippery characteristics. Such coatings can significantly enhance corrosion resistance by minimizing water-metal contact and promoting self-cleaning effects. This review presents various strategies for fabricating corrosion-resistant metallic coatings, including different electrodeposition techniques in aqueous or non-aqueous baths, followed by post-treatment procedures and surface functionalization methods. However, despite the promising protective properties demonstrated under controlled laboratory conditions, long-term studies under natural exposure conditions are still lacking, which limits the full assessment of the durability and effectiveness of non-wettable electroplated deposits in practical applications.

Keywords: corrosion resistance; electrodeposition; slippery coatings; superamphiphobicity; superhydrophobicity; superoleophobicity; surface modification.

Figure 1

Exemplary schematic topographies of non-wettable solid surfaces.

Figure 2

Epicuticular wax crystals on leave surfaces: (a) lotus—upper side, (b) lotus—underside, (c) myrtle spurge Euphorbia myrsinites, (d) Adam’s needle Yucca filamentosa, (e) wild cabbage Brassica oleracea, and (f) mottlecah Eucalyptus macrocarpa. Reproduced from [33] under License CC BY 2.0.

Figure 3

Traces of natural erosion of wax crystals on leaf surface: (a) lotus Nelumbo nucifera—upper side, (b) myrtle spurge Euphorbia myrsinites, (c) wild cabbage Brassica oleracea, and (d) Adam’s needle Yucca filamentosa. On the papillose leaves (a,b), the eroded areas are limited to the tips of the papillae, while the damaged areas can be much larger on non-papillose cells. Reproduced from [33] under License CC BY 2.0.

Figure 4

Surface topography of springtail cuticles (a,b) featuring three levels of wettability protection (b). Reproduced from [97] under License CC BY 4.0.

Figure 5

Morphology of pitcher plant Nepenthes gracilis. (a) Pitcher with visiting ant (A—epicuticular wax crystal surfaces visible on the inner pitcher wall and on the underside of the pitcher lid; B—horizontal position of the lid above the pitcher opening facilitates prey capture). (b) Structure of the wax crystal layer on the inner pitcher wall (A—top view; B—side view). Reproduced from [118] under License CC BY.

Figure 6

Electrodeposited non-wettable metallic coatings—SWOT analysis.