Hydrogen permeation through high-temperature resistant metals can be reduced by three orders of magnitude at 800 °C by means of protective layers of several jam thickness produced by controlled preoxidation. The coating conditions must be adjusted individually to the various alloys. With the alloys under investigation, the following parameters have proven successful: steam or steam/H2, 900 to 1000°C, thermocycling mode of oxidation with intermediate cooling periods.