Corrosion of the wall of an agitated vessel containing pulp-fiber suspensions was studied using an accelerated test which involves the diffusion controlled dissolution of copper in acidified dichromate. Variables studied were pulp slurry flow rates, slurry concentrations and pulp fiber size. Three different pulp sizes were studied, namely: fiber-pulp slurry, fine-pulp slurry and the whole-pulp slurry. The rate of mass transfer controlled corrosion of copper was found to increase with increasing slurry flow rate and decreased by increasing pulp slurry concentrations. Fines in pulp slurry were found to play a major role in decreasing the rate of diffusion controlled corrosion due to its ability to damp small scale eddies at the wall of the agitated vessel  in a manner similar to drag reducing polymers in pipes. Percentage inhibition efficiency using fine- pulp slurry ranged from 40% to 76%, while for the whole-pulp slurry the value ranged from 28% to 47%, when pulp slurry concentration ranged from 0.1% to 0.4%.