A gas wiping device for controlling the thickness of a coating layer deposited on a running metal strip plated with molten metal in an industrial hot-dip installation, comprising a main nozzle unit and a secondary nozzle unit, to blow a wiping jet on the surface of the running strip, said main nozzle unit and secondary nozzle unit being respectively provided with a main and secondary chamber (6, 6A) fed by pressurized non-oxidizing gas and with at least a main and secondary elongated nozzle slot (7, 7A) formed in the tip of the respective main and secondary nozzle units (5, 5A), said tips comprising each an external top side (13, 13A), facing in use the downstream side of the running strip, and making an angle with the running strip surface, wherein the secondary nozzle unit is adjacent the main nozzle unit over the external top side of the main nozzle unit tip, so that the upper external surface of the secondary nozzle unit is designed to form, in use, an angle with the running strip surface comprised between 5° and 45°, wherein the thickness of the second slot opening is comprised between 1.5 and 3 times the thickness of the first slot opening, characterized in that the tip of the secondary nozzle unit has an external top side prolonged downstream by a first baffle plate making a first angle in use with respect to the running strip, so as to form a gas confinement region and in that the gas wiping device also comprises also: - an actuator capable to adjust a distance (d, d') between a tip of the first baffle plate and the running strip 1 said first baffle plate being mounted pivotable in respect of the second nozzle upper surface thanks to a hinge, so that said actuator is capable to modify an angle between said first baffle plate and said second nozzle upper surface; - an oxygen sensor provided in the gas confinement region, dose to the second slot opening of the secondary nozzle unit, for measuring the amount of oxygen close to the running strip. downstream of the nozzle location, said measurement allowing to activate the actuator and further to modify the geometry of the gas confinement region, especially by varying said distance (d, d'), in order to reduce, when needed, the oxygen content in the gas confinement region, or to keep the oxygen content therein below a predetermined threshold. - an actuator capable to adjust a distance (d, d') between a tip of the first baffle plate and the running strip 1 said first baffle plate being mounted pivotable in respect of the second nozzle upper surface thanks to a hinge, so that said actuator is capable to modify an angle between said first baffle plate and said second nozzle upper surface; - an oxygen sensor provided in the gas confinement region, dose to the second slot opening of the secondary nozzle unit, for measuring the amount of oxygen close to the running strip. downstream of the nozzle location, said measurement allowing to activate the actuator and further to modify the geometry of the gas confinement region, especially by varying said distance (d, d'), in order to reduce, when needed, the oxygen content in the gas confinement region, or to keep the oxygen content therein below a predetermined threshold.