Abstract The performance of three aluminium anode materials has been evaluated for a sub-sea gas transmission line with an external sour environment. Anode capacity tests were carried out in simulated service environments containing sour sea water with 10 ppm H2S and 2000 ppm H2S and sour sediment with 1000 ppm H2S. Comparative tests were undertaken in control environments with aerated non-sour sea water and sediment. Standard testing to DNV RP B401 was also undertaken. All testing was at 20°C. The results show no systematic difference between the performance of the three test materials in each test environment. High anode capacities were measured in the non sour sea water tests and RP B401 tests. Similar high capacities were obtained in sour sea water with 10 ppm H2S. Lower capacities were measured in the non sour sediment compared to non sour water. The effect of increasing H2S levels resulted in severe localised corrosion of the materials and significantly reduced capacities.