A method for controlling surface reactions on a steel strip running through a furnace includes, successively, a first section, a second section, and a third section separated by a sealing element, an atmosphere in the second and third sections being oxidizing and reducing respectively, the method including: heating, in the first section, the steel strip to between 600 and 750° C., while causing the atmosphere therein to be slightly oxidizing and to include: an H2 content inferior to 2%; an O2 content inferior to 0.1%; an H2O or CO2, or H2O+CO2 content superior to 0.03%; a controlled dew point ranging from −50 to −15° C.; and a controlled concentration of CO+CO2 maintained below 2%. All percentages are expressed in terms of volume.