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The goal of the present experiments was to obtain crack heating of hydrogen attack (HA) in low-carbon steel by heat treatment. It was observed by scanning electron microscopy (SEM) that HA cracks experienced different heating effects. The results indicated that HA cracks less than or equal to10 mum in length can be heated completely by cyclic heat treatment between room temperature and 1, 000degreesC. Five cycles totaling 10 h were used. The studies performed showed that crack heating is controlled by diffusion and that the recovery kinetics depend on the plastic deforming energy, E., arising from the growth of HA bubbles or cracks. These findings led to the conclusion that the critical condition for healing of bubbles or cracks is E-S greater than or equal to 2 gamma/r (where gamma is the surface tension and r is the radius of bubbles or the half-length of cracks), provided the atoms of H, C, and Fe can diffuse rapidly.