Diffusion-controlled impingement corrosion of the lower part of the inner cylinder of an annulus caused by a perpendicular inlet jet was studied using the diffusion-controlled dissolution of copper in acidified dichromate technique. Variables studied were solution velocity, physical properties of the solution, diameter of the perpendicular feed nozzle, and the effect of drag-reducing polymers. For blank solution, the rate of mass-transfer-controlled impingement corrosion was correlated by the equation Sh = 2.74Sc(0.33) Re-0.46 (d(n)/d)(-0.4). Drag-reducing polymers were found to decrease the rate of mass-transfer-controlled impingement corrosion by an amount ranging from 29.9 to 68.9% depending on electrolyte concentration, polymer concentration, and feed nozzle diameter. The importance of the present results to the design of annular equipment was noted.