Process and apparatus for in situ electroforming a structural layer of metal bonded to an internal wall of a metal tube

A process for in situ electroforming a structural reinforcing layer of metal bonded to an internal wall of a degraded section of metal tube, comprising:

• mechanically cleaning the internal tube wall surface in said tube section;
• inserting a probe into the metal tube and moving it so that it spans the degraded tube section, the probe having an electrode extending substantially along its length, sealing means at each end for containment of fluids within the tube section, and circulation means for flowing fluids into and out of the tube section;
• electrodepositing a strike layer of metal on the internal wall of the tube section by flowing an electrolyte containing at least one metal salt of interest through the section and applying a direct current between the electrode and the metal tube to cause the electrodeposition of a metal layer not exceeding 10 .mu.m thick;
• and
• electroforming a structural layer of metal on the strike layer by flowing an electrolyte containing at least one metal salt of interest through the section and applying a pulsed direct current between the electrode and the metal tube at a pulse frequency of 100 to 1000 Hz with a duty cycle in the range 10 to 40% for a sufficient time to electroform a metal layer 0.1 to 2 mm thick, so that the tube section is restored to its original mechanical properties, said structural electroformed layer having an ultrafine grain microstructure which provides the layer with a high degree of hardness, stiffness and strength while maintaining excellent ductility.