Use of caffeine-containing MIL-100 (Fe) metal organic framework as a high-performance smart anticorrosion coating to protect stainless steel in 3.5 wt% NaCl solution

In this study, caffeine-loaded MIL-100 (Fe), caffeine@MIL-100 (Fe), was used as a smart corrosion-inhibiting coating to protect 308L-16 stainless steel (308L-16 SS). For this purpose, a thin film of the smart anticorrosion caffeine@MIL-100 (Fe) coating was deposited on an 308L-16 SS surface using a decanoic acid self-assembled monolayer. A significant encapsulation efficiency for caffeine loading in the MIL-100 (Fe) metal organic framework was obtained as 17.8%. The experimental data indicated that the caffeine@MIL-100 (Fe) coating would release the caffeine very rapidly as the solution became acidified around the corrosion sites and formed a protective layer to prevent from penetrating solution into the substrate. The EIS results and the Tafel plots showed that the proposed smart coating has an excellent performance to protect 308L-16 SS from corrosion in saline media. Based on the results, decreasing the solution pH would cause the MIL-100 (Fe) framework to decompose and subsequently release caffeine at the 308L-16 SS surface.