Chemical milling

A method of clearing a deposit from a monolithic metal tube interior comprising:

• dc coupling the tube to a counter electrode having a natural E° greater than the natural E° of the tube, such dc coupling being accomplished without imposition of an external positive voltage from the counter electrode to the tube;
• coupling a fluid conduit between the tube and the counter electrode;
• associating an electrolyte with the counter electrode;
• and
• thereafter, with the tube and counter electrode dc coupled, flowing the electrolyte from the counter electrode through the fluid conduit to the tube and passing the electrolyte through the interior of the tube.

A tube-clearing system comprising:

• a monolithic metal tube having an interior surface and a hollow interior for flow of fluid therethrough;
• a counter electrode having a natural E° greater than the natural E° of the tube;
• an electrical conductor dc coupling the tube and the counter electrode without imposition of an external positive voltage from the counter electrode to the tube;
• an electrolyte;
• and
• a fluid conduit through which the electrolyte passes, the conduit fluidically coupled to the dc coupled tube and counter electrode so as to associate the electrolyte sequentially with the counter electrode and the hollow interior of the tube whereby to remove deposits from the interior surface of the tube.

A method of clearing a deposit from a monolithic metal tube interior comprising:

• dc coupling the tube to a counter electrode having a natural E° greater than the natural E° of the tube, such dc coupling being accomplished without imposition of an external positive voltage from the counter electrode to the tube;
• imposing an external power source in a negative sense from the counter electrode to the tube;
• associating an electrolyte with the counter electrode;
• and
• passing the electrolyte through the interior of the tube.