During the past few years particular attention has been paid to the protection of metal parts of engineering structures of all kinds against corrosion. The problem of protecting metal structures against deterioration is now recognised as of primary concern both to users and to manufacturers. Corrosion prevention is an economic problem and its cost must be based on the cost of preventative measures compared with the loss directly and indirectly due to deterioration. In those sections of industry in which marked advances have occurred in corrosion prevention, the advances can be seen to be the result of close co-operation between the laboratory, manufacturers and users.