CRITICAL EFFECT OF PH ON THE FORMATION OF ORGANIC COATINGS ON MILD-STEEL BY THE AQUEOUS ELECTROPOLYMERIZATION OF 2-VINYLPYRIDINE

Coatings of poly(2-vinylpyridine) have been formed on mild steel subst rates in aqueous medium by electrochemical polymerization of the 2-vin ylpyridine monomer. The pH of the solution has been found to be critic al for this electropolymerization coating process. At low pH (below 3. 5), even with an efficient initiation reaction, the propagation proces s was impeded and no substantial polymer film was formed. At high pH ( above 6.0), only a thin and irregular film formed due to the lack of a n effective initiation reaction. Only when the solution pH is in the r ange of 4 to 5.5 can good quality coatings be formed on mild steel sub strates. The detailed effects of the pH on the electropolymerization a re discussed in terms of a proposed free radical polymerization mechan ism. This research has also resolved the issue of some of the non-repr oducible experimental results reported in the literature and confirmed the feasibility of forming poly(2-vinylpyridine) coatings on a mild s teel substrate by electropolymerization of the monomer.