Magnetite Dissolution and Crevice Studies with Chelant Solutions

Work is described in two related areas: (a) fundamental studies of the dissolution behavior of synthetic magnetite in aqueous chelant solutions as functions of solution pH, temperature, heating time, chelant structure, and the presence of additives, and (b) more applied investigations in which information from the basic studies was utilized in choosing solutions and experimental conditions for the removal of magnetitebased corrosion products from simulated steam generator tube-tube support plate crevices. The magnetite dissolution work has employed a novel, convenient, and sensitive experimental technique based on the ferromagnetism characteristic of Fe₃O₄. Since chemical reaction of magnetite with chelants results in nonmagnetic iron chelates, monitoring the ferromagnetism of a reaction mixture, as a whole, provides an in situ and quantitative measure of unconsumed magnetite.