INTERNALLY OXIDIZED PIPES

摘要

Corrosion damage to tubes made of copper or copper alloys by local pitting is usually triggered by the residues of drawing oil located on the inner surface and/or by oxide layers of poor adhesion. To achieve an especially high resistance of internally oxidised tubes to pitting or to prevent an uneven formation or detachment of the oxides located on the inner surface, according to the invention the thickness of the copper-oxide layer adhering to the basic metal is limited to values of between 0.01 and 0.2 mu m. Preferably, the copper-oxide crystals have a maximum grain size of 0.5 mu m and possess an oriented structure. The good adhesion of the copper-oxide layer formed on the inner surface of the tube preferably by continuous annealing is preserved even when the tubes have been subjected to a machining reducing their cross-section, for example by bending or drawing.