PURPOSE: To facilitate the evaluation of corrosion resistance even if the corrosive condition is moderate or the covered metal has excellent corrosion resistance by a method wherein the hydrogen, produced by the corrosion reaction, penetrates and dissolves into the metal from the surface of the metal under a covering film and this hydrogen is detected at the back side of the covered metal.

CONSTITUTION: A covering 2 such as coating or lining is applied to one side of a covered metal 1 and the covered metal 1 is placed between a test-cell container 3 and a measurement-cell container 4 and corrosive solution or corrosive gas is supplied by a corrosion condition setting equipment 12 under the prescribed condition. The metal surface under the covering 2 of the covered metal 1 is corroded. Hydrogen ion, produced by the cathode reaction due to the corrosion, is converted into atomic hydrogen on the metal surface and a part of it penetrates and dissolves into the metal and is diffused to the uncovered side of the metal. The hydrogen which reaches the metal sur face 5 is discharged into the measurement-cell container 4. The discharged hydrogen is introduced into a mass analyser 11 through a pipe 7 and its concentration is recorded with the passage of time.