From Accelerated Aging to Natural Exposure: Environmental Durability and Aging Behavior of Ethyl Cellulose-Based Supramolecular Gel Coating

Ethyl cellulose (EC)-based supramolecular gel coatings are melt-coated and conformable to complex geometries, but their durability under coupled environmental exposures remains unclear. Here, C-EC, C-EC/TPU, and C-EC/Fe3O4 coatings were subjected to 600 h UV aging, 150 days of immersion in 3.5 wt.% NaCl, 150 days neutral salt spray, and ten exposure–remelting–reapplication cycles. Natural exposure was conducted for up to 360 days in Wanning and Qingdao, whereas only C-EC was applied to pipes, angle sections, bolts, and flanges. Single-factor tests revealed exposure-dependent changes in surface morphology, optical properties, tensile strength, and ester-related FTIR features. Natural exposure additionally involved atmospheric deposition, localized fouling, seasonal variation, and fungal presence. After 360 days in Qingdao, all three coatings exhibited gloss values below 1 GU. In Wanning, an Aureobasidium-dominated fungal community was detected in material from discolored areas of a C-EC-coated flange and pipe. After C-EC coating removal from structural components, no obvious macroscopic rust was observed in the examined covered regions. SEM showed increased surface heterogeneity, while FTIR revealed changes in ester-related absorption features. Oil redistribution or loss, hydrolysis, and oxidation were not directly measured and remain possible degradation processes. Laboratory and natural exposure should therefore be correlated through shared observable aging features rather than direct time equivalence.