In the present study the film formation growth rate has been monitored by electrochemical and optical measurements. Video sequences of the electrode surface have been analysed with respect to grey level by use of a MATLAB (R) programme in order to follow the kinetics of film formation. Parameters such as pH, the concentration and type of sulphur species as well as applied potentials have been varied. The rate of the film formation was quantified by video monitoring followed by picture analyses. Sulphide and thiosulphate formed the densest film at high pH, while sulphite and dithionite formed the densest film at low pH. (c) 2005 Elsevier Ltd. All rights reserved.