Copper Electropolishing in Phosphoric Acid under Normal and Forced Convection Conditions in Presence of Some Pharmaceutical Drugs

Some pharmaceutical drugs namely valsartan, hydrocholorothiazide, erythromycin thiocynate and diclofenac potassium were studied as chemical additions for enhancing the finished copper surface attained. Anode potential-limiting current relationship was measured and comparing of gradually increasing pharmaceutical compound concentrations (from 1 × 10-4 to 7 × 10-4 M). Copper dissolution behaviour in presence of pharmaceutical compounds was studied under natural convection [rotating cylinder (RCE) and rotating disc electrode (RDE)] as forced convection. The limiting current was found to diminish with enlarging additives concentration and increase with increasing temperature (293-313 K). Activation energies values confirm that reaction rate was diffusion controlled. The results showed that the improvement produced in electropolishing in presence of pharmaceutical compounds occurs through adsorption of their molecules above metal surface. All the pharmaceutical compounds adsorption process obey kinetic-thermodynamic model. The data under different conditions were controlled by dimensionless correlations viz. Sherwood, Schmidt and Reynolds numbers. Surface morphology also confirmed that an addition of pharmaceutical compound to copper dissolution bath enhance surface appearance and its texture quality to great extent.