The effect of decaying Swirl flow on the rate of diffusion controlled corrosion of a pipe was studied by using the diffusion controlled dissolution of copper in acidified dichromate. Variables studied were flow rate, physical properties of the solution and length of the tube. The data were correlated by the equation Sh = 4.14Sc(0.33)Re(0.56)(L/d)(-0.38). The effect of polyox WSR-301 drag reducing polymer on the rate of diffusion controlled corrosion of the pipe was also studied, the polymer was found to decrease the rate of corrosion by an amount ranging from 3 to 26% depending on the operating conditions.