The hydrogen evolution reaction (HER) on and the hydrogen entry into iron were studied using the rotating disk electrode (RDE) and the electrochemical permeation technique. A long-lasting negative polarisation of iron modified the metal surface and it resulted in significant changes in the kinetics of the HER and in the efficiency of hydrogen entry. Possible electrochemical reactions on the iron RDE in a slightly acidified solution were described and were then used for the detailed analysis of the experimental polarisation curves measured on the cathodically modified iron surface. A strong increase in the efficiency of hydrogen entry was attributed to a higher hindrance of the HER, which was expressed by an increase of the Tafel slope. (c) 2005 Elsevier B.V. All rights reserved.