To provide the subject corrosionproofing structure designed to resolve such problems that when rotating shafts, rotating plates or rotating plate rings are made of different kinds of metals, a corrosion occurs due to the ionization tendency difference among the different metals, resulting in their corrosion, shape damage, appearance spoilage, etc.; if such shape damage of the rotating plates such as at the corners and/or surfaces occurs, e.g. a smooth revolution of a mixed liquid formed by the rotating plates cannot be secured, resulting in a hindrance in separating raw laver from contaminants.

This corrosionproofing structure is such that, in a raw laver contaminant separator, there is equipped a corrosionproofing means between the rotating plates and rotating shafts; wherein the raw laver contaminant separator is so designed that a raw laver mixing liquid tank 2 is furnished with the rotating shafts 33 for separatory casing 31, rotating plates 32, a raw laver feed port 11, a seawater feed port 12 and a contaminant discharge port 4 and raw laver and contaminants are separated via a clearance A defined by the rotating plates 32 and separatory casing 31. Thus, the problems described above, including contamination of corroded, broken metallic chips into raw laver, can be resolved.