Hydrogen diffusivities in cold rolled and annealed Cu have been measured at 22℃ by time lag method, based on electrochemical permeation technique. In the first series of the experiment, cold rolled specimens have been annealed at 750℃ for 24 h. The diffusivity of hydrogen in the specimen annealed at 750℃ is slightly higher than that in the cold rolled specimen, suggesting that the dislocation can act as a weak trap site of hydrogen. In the second series, cold rolled specimens have been at 750℃ for 24 h and then at 950℃ for 5 min, and subsequently quenched into cold water. Electrical resistivity and diffusivity have been measured in the quenched specimen during annealing at 80℃. With increasing annealing time, the resistivity decreases in an exponential way and the diffusivity increases, implying that the vacancy acts as trap site of hydrogen. These experimental results are opposite to previous results. In the previous investigations, it was proposed that vacancy and dislocation were not hydrogen trap site in Cu. The discrepancy between the present and the previous results has been discussed.
