CONDOROIL: in line electrolytical pickling

In the production of Tig and laser welded stainless steel tubes, the labor cost represents, in Western countries, more than 50% of the total operation costs. Pushed by the strong competition, tube manufacturers are more and more equipping the profiling machines with a series of in line treatments in order to reduce the necessity of handling the material. The most difficult component to be installed in the line has always been the pickling process, that has to follow the induction annealing furnaces, considering that the traditional pickling were requiring long time and dangerous substances in the production area (like nitric and hydrofluoric acids). In cooperation with a major player in the tube manufacturing CONDOROIL developed in year 2000 the first in line electrolytical pickling tunnel.   In the pickling tunnel the material pass inside the treatment section where the surface is subject alternatively to anodic and cathodic currents that, together with an electrolytic solution of non-toxic pickling product, carry out the pickling action in a very short time, approx. 15-20 seconds.
The pickled material is then rinsed with three back current stages and then dried with air.In particular, the anodic section allows to solubilize the depleted chromium layer and to passivate the material, while the cathodic section makes the oxide expulsion easier thanks to the gas evolution that is three times higher than in the anodic section.
At the tunnel exit, the tube is ready to be marked, cut and packed directly on the line, limiting handling operations. Since the first unit built in year 2000, many improvements have been carried out and nowadays are proposed closed loop units with total recovery of acids, recovery of metals in metallic form, re-concentration and recovery of the drag out and demi recycling of the water through reverse osmosis concentration unit. Furthermore, with the use of different electrolytic solutions, it has been possible to realize the first electro polishing in line tunnel.