Electrochemical copolymerization of N-methylpyrrole (NMPy) and indole (In) in various monomer ratios were carried out by potentiodynamically methods in acetonitrile electrolyte containing LiClO 4 on gold electrode. The obtained homopolymers and copolymers were characterized with cyclic voltammetry (CV), in situ UV-Visible, FT-IR spectroscopy, scanning electron microscopy (SEM) and in situ resistivity measurements. The cyclic voltammetry study shows that the onset potential for the monomers and co monomers curves is located at the different values for N-methylpyrrole, indole and N-methylpyrrole-indole. There is a nucleation process followed by growth of nuclei to continuous films. The oxidation and reduction peaks for copolymer, P(NMPy-In), which synthesized from the 1:1 mole-mole ratio concentration of the relevant monomers, located between those for poly Nmethylpyrrole (PNMPy) and polyindole (PIn) films. The observed values were showed a decreased [NMPy]/[In] ratio concentration in the copolymers shifts the peak potential to more positive. The in situ UV-Visible, FT-IR spectroscopy and SEM analysis of homopolymers and copolymers were also studied. The result shows the intermediate spectroscopic properties between homopolymers and copolymers. The in situ resistivity measurements showed that the copolymers have a lower conductivity than the corresponding parent homopolymers.

The short electrode life is one of the most important problems associated with resistance spot welding of galvanised steel sheets. In this study, a nanolayered multi-layer CrN/(Cr,Al)N coating was deposited on the tip of the electrode by applying the cathodic arc physical vapour deposition process with the layer thickness of about 30 nm and an overall thickness of 1.1 µm. The electrode life test confirmed that the coating could extend the electrode life up to 125%. The coated electrode showed a significantly lower growth rate (∼0.3 µm per weld), in comparison to the un-coated one (∼1 µm per weld). The degradation of the electrode could be subdivided into two subsequent steps: the degradation of the electrode periphery and the degradation of the electrode tip. The CrN/(Cr,Al)N coating could effectively protect the electrode tip periphery from zinc adhesion and postpone the first stage electrode degradation which delayed the second one.

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