Dissolution of cobalt from hard metal alloys by cutting fluids

On grinding hard metal alloys containing cobalt, the dissolution of cobalt during 5 days was studied for nine commercial cutting fluids. After 1 day, a major part of the cobalt liberated from the material ground is found in solution. This percentage decreases when grinding is continued using the same coolant fluid. Only a small fraction of the cobalt is found in particles in the circulating fluid. The bulk must be in the sediment in the storage tank, where it does no harm to the workers' skin. The final concentration of cobalt found in some fluids may be hazardous.