This image, which is also in the main story, is of scooping up water with a colander coated with Sweat Barrier. The Sweat Barrier is not simply a film on the metal surface to prevent contact between sweat and metal. This would require a thick film.
The film created by the sweat barrier has the property of repelling liquids well. For this reason, even a thin film can exhibit a high effect. Since the film is thin, it is easy to handle with a smooth liquid. Since the film is thin, it does not change the appearance of the accessory at all. Do all the good things.