This invention relates to the use of a water soluble maleate salt, preferably disodium maleate, as a scale converter. Such salts convert scale into a water soluble compound which is capable of aqueous removal without the conventional step of employing either (1) an acid wash or (2) a sequestering agent.
A process for reducing hydrogen sulfide gas evolution during dissolution of ferrous sulfide with an aqueous acidic solution comprising contacting the ferrous sulfide with an aqueous acidic solution containing an effective amount of an additive comprising at least one member selected from the group consisting of maleic acid, maleic anhydride and the alkali metal and ammonium salts of maleic acid. The aqueous acidic solution also can contain corrosion inhibitors.
A method of removing ferrous sulfide from ferrous metal surfaces comprising contacting the ferrous sulfide with an aqueous composition comprising an acid selected from the group consisting of maleic acid, maleic anhydride, and the alkali metal and ammonium salts of maleic acid.
A method of removing metal scale from surfaces that includes contacting the surfaces with a first aqueous solution of a chelating agent, allowing the chelating agent to dissolve the metal scale, acidifying the solution to form a precipitant of the chelating agent and a precipitant of the metal from the metal scale, isolating the precipitant of the chelating agent and the precipitant of the metal from the first solution, selectively dissolving the precipitated chelating agent in a second aqueous solution, and removing the precipitated metal from the second solution is disclosed.
