Abstract: Process and apparatus for degreasing and cleaning metal strips (3) traveling at high speed in a liquid (2) by bringing them into contact with a diverting roll (4). The roll (4) has a surface of contact with the strip (3) which comprises circumferential grooves (18). A gas is introduced into the liquid (2) in the vicinity of the surface of the roll (5) so that the fluid entrained between the strip (3) and the roll (4) is a compressible mixture of liquid and gas. In particular, when the liquid (2) is an electrolyte, the gas release can be produced by means of electrodes (10, 11). A hood (12) enables the gas released to be retained in the vicinity of the contact surface of the roll.

Abstract: The invention relates to an acid pickling tank for metal strips with a width equal to or greater than 0.50 meter.The tank incorporates an external supporting structure (1) and a metal casing (3) coating internally with rubber (6). The rubber layer (6) is lined internally with large slabs (10a, 10b) of a natural rock of volcanic origin, which has a total SiO.sub.2 and Al.sub.2 O.sub.3 content greater than 60%, a porosity of between 6 and 30% and a relative density of less than 3. At most three slabs (10b) are placed side by side along the width of the tank and at most one slab (10a) is placed along its height. The minimum dimensions of a slab (10a or 10b) are 0.50.times.0.50 meter.The invention is applicable in particular to the pickling of strips of hot-rolled metal sheets.