AbstractEarlier work had suggested that surface‐active agents played a more specific role in corrosion processes than was generally supposed. A series of sodium alkyl sulphates were prepared, and the behaviour of tin specimens immersed in their dilute aqueous solutions was examined. Some weight‐loss experiments were made, and the effects of constitution and concentration upon corrosion rate determined.The corrosion was not general, but essentially a point attack, so that a note of the distribution of corrosion, as well as of its extent, was made. Theory suggests that the readiness with which a solution corrodes tin lies in its ability to dissolve the existing protective oxide layer on the metal surface. However, experiments showed that stannic oxide was insoluble in neutral solutions of any of the materials used.Further experiments involving breakdown‐potential measurements and pressure tests on stripped oxide films revealed that the surface‐active solute ruptures, rather than dissolves, the oxide film. This film is generally sufficiently stressed for many potential cracks to exist. Adsorption of a surface‐active solute on the surfaces of these cracks so reduces their adhesion that they develop into actual failures, and ultimately into corrosion sites. The subsequent activity of these sites is controlled in part by the structure of the adsorbed layer of solute at the meta