Manual and instrumental procedures for polishing 1 and 6 pm radius platinum microdisc electrodes were compared by performing a statistical evaluation of three basic electrochemical signal characteristics measured from steady-state voltammograms for oxidation of ferrocene in acetonitrile. The three signal characteristics measured were the limiting current Ilim, the half-wave potential Ell2 and the (E3/4 -E1/4) potential difference, where E3/4 and E1/4 are the potentials at three quarters Zlim and one quarter Zlim, respectively. Fisher-Snedeckor F-test and Student's t-test statistical data are presented together with corresponding critical values for the three electrochemical parameters obtained in the manual and instrumental polishing modes. The reproducibility of all measured data is significantly improved when the electrode is polished after each experiment. The mean values of the limiting currents were significantly better using the instrumental rather than the manual polishing method. However, with respect to uncertainty of the experimental values, instrumental polishing gave the best estimates of the measured parameters; confidence intervals were very small for and (E3/4 -E1/4) potential measurements, being ltO.20 and lt0.36 mV for E1/2 values and 0.11 and 0.19 mV for (E314 -E1/4) at 1and 6 pm electrodes, respectively. The instrument designed for polishing microelectrodes is also described.

Electrically conducting polypyrrole films doped with dodecylbenzenesulphonic acid (PPy-DBSA) have been electrochemically polymerized on stainless steel. The surface and electrochemical properties of the films were investigated by a combination of cyclic voltammetry (CV), scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS). The CV results showed an irreversible reaction of electropolymerization. All PPy-DBSA films had a nodular or cauliflower-like surface morphology. The grain size was dependent on the growth current density and the growth time. The ratio of incorporated DBSA anions to pyrrole repeat units in the films was ∼1 : 2. The doping level, calculated from the positive charge accumulated in the polymer chain (at.% ratio .N + + N 2+ //N total /, varied as a function of the growth current density and the growth time. The maximum doping level occurred at a growth current density of 0.5 mA cm −2 , consistent with an oxidation peak of the pyrrole monomer observed by CV. The interfacial layer between the polymer and substrate was also studied. A sulphur-rich layer was observed, indicating the presence of a thin layer of DBSA at the interface. In addition, iron was detected on the metal side of the film as a result of its dissolution from the stainless-steel electrode during the electropolymerization process. These results have implications for the use of polypyrrole films as environmentally friendly corrosion mitigants.

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