This paper describes the cathodic protection retrofit undertaken on four steel gravity platforms installed in 1976 offshore West Africa in 86 m deep waters. They were originally protected with galvanic anodes with a design life of 20 years. Insufficient protection conditions were measured on all the structures after only 10 years. A retrofitting intervention was planned in 1987 using an Impressed Current System using the LIDA TSA TM concept. The main feature of the retrofit system are: ; N. 10 LIDA TSA TM strings on each platform; ; each string supports N. 10 anodes, type LIDA® SW.T.2.5/100; ; total anode current capacity for each platform: 5,000 A for a total installed capacity of 20,000 Amps The systems were successfully commissioned in 1987: protection conditions were achieved and continuously maintained from start up with a current output of 50 – 60 % of the total installed anode current. In 2003 the Oil Company decided to extend the life of the four platforms for other 20 years and planned a number of interventions to guarantee the structure integrity for the new residual life. It was decided to fully renew the CP system using the same technology successfully in service. After 18 years of operation, the entire CP system was replaced in 2005 using LIDA TSA™; the refurbished system was successfully commissioned in 2005 with a 20 years expected design life.