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Although Cu and Ni recovery at the Indian National Metallurgical Laboratory, Jamshedpur, was more than 90%, Co recovery was only 50-60%. Dissolution studies using pure metal powders showed that the presence of metallic Fe and Mn in the leaching stage was detrimental to Co recovery. Tests were carried out on various additives, some of which improved Co recovery without affecting the Cu and Ni recovery rates. Electrochemical studies were carried out on the Fe-Co alloy which is likely to form during the reduction roasting stage and is difficult to leach in an ammoniacal system. Potentiodynamic polarisation studies of the alloy in ammonia solution showed that the alloy system was pre-passivated at open circuit potentials. Addition of some additives caused increased dissolution of the Fe-Co alloy. The leaching of roasted sea nodules in the presence of these additives resulted in an improvement in Co recovery to about 80%., Although Cu and Ni recovery at the Indian National Metallurgical Laboratory, Jamshedpur, was more than 90%, Co recovery was only 50-60%. Dissolution studies using pure metal powders showed that the presence of metallic Fe and Mn in the leaching stage was detrimental to Co recovery. Tests were carried out on various additives, some of which improved Co recovery without affecting the Cu and Ni recovery rates. Electrochemical studies were carried out on the Fe-Co alloy which is likely to form during the reduction roasting stage and is difficult to leach in an ammoniacal system. Potentiodynamic polarisation studies of the alloy in ammonia solution showed that the alloy system was pre-passivated at open circuit potentials. Addition of some additives caused increased dissolution of the Fe-Co alloy. The leaching of roasted sea nodules in the presence of these additives resulted in an improvement in Co recovery to about 80%.