Abstract: An apparatus for providing electrochemical corrosion protection to a process vessel, the apparatus comprises at least one anode in communication with the process vessel; a DC current supply being electrically coupled to the process vessel and to the at least one anode; and a potential control unit in communication with the DC current supply. The potential control unit is electrically coupled to the process vessel and to a reference electrode in communication with the process vessel. The current supplied by the DC current supply for passivating the process vessel is adjustable by the potential control unit. The process vessel may comprise at least one of duplex stainless steel and superaustenitic stainless steel.

Abstract: In combination, a storage tank having a metal bottom, compacted electrolytic backfill below the tank bottom and a cathodic protection anode within the backfill below the tank bottom. The anode is in the form of a generally continuous ribbon that is shaped to follow a serpentine path corresponding generally in shape to the tank bottom. A feeding cable network is connected directly to the anode.

Abstract: In a system for cathodically protecting an underground metallic structure where a sacrificial anode material encasing a metal core is in electrical communication with the structure, the core can be automatically and galvanically disconnected from electrical communication with the structure after the anode material has been consumed, by inserting in series between the structure and the core a corrodible link made of a material which is less galvanically active than the anode material but more galvanically active than the material of the core. At least a portion of the corrodible link is exposed to the underground environment, so that upon consumption of the anode material, the corrodible link will corrode and break the connection between the core and the underground structure.

Abstract: Sodium polysulphide is formed by reacting sodium sulphide and sodium sulphur-oxygen salts in the presence of carbon and oxygen. The invention is particularly applicable to reacting recovery furnace smelt from a polysulphide pulping process to form a mixture of sodium polysulphide and sodium carbonate which is substantially free from sodium sulphur-oxygen salts, so that dead-load sulphidity is substantially eliminated from the pulping liquor.