iron cement
A composition especially prepared for filling the joints, holes, and other small openings which hold water and cause oxidation. It is therefore not a cement in the usual sense, but is a paste only. The largest part of its substance is composed of iron borings or filings, which must be clean and fresh without oxidization; this powder is held together by a glutinous or adhesive paste, for which there are many formulae. (Sturgis, 1900)