CHARACTERIZATION AND EVALUATION OF CORROSION BEHAVIOR OF CONDUCTING POLYMER COMPOSITE COATINGS
Intrinsically Conducting Polymers (ICPs) and their composite coatings were successfully electrodeposited on aluminium alloy AA-2024 substrate from an aqueous solution containing oxalic acid and monomers. The monomers used were pyrrole (Py), aniline (ANi) and metanilic acid (MAA). Electropolymerization was done using constant potential, constant current and cyclic voltammetry methods. The applied potential, applied current, monomer concentration, co-monomer feed ratio and reaction time were varied and their effect on the yield and corrosion performance were assessed. The progress of electropolymerization was monitored by using coating thickness measurements, current - time (I-t) and potential-time (E-t) transients.The coatings were characterized by reflection-absorption infrared spectroscopy (RAIR) and scanning electron microscopy (SEM). The corrosion performance of the ICPs and their composites were determined by using DC Polarization (DCP) studies.The corrosion rate of the coatings was found to increase with increasing deposition time. The yield and thickness of the coatings increased proportionately with time. SEM micrographs showed that the size of the grains increased as the reaction time was increased. A small amount of yttria stabilized zirconia (YSZ) was added into the reaction medium and the corrosion performances were evaluated. It was found that the presence of YSZ in the polymer matrix lead to a significant decreases in corrosion rate. X-Ray diffraction analysis was used to study the presence of YSZ in these coatings. SEM micrographs of polypyrrole (PPy) and polymetanilic acid (PMAA) showed microsheroidal and grainy morphology of the coatings, respectively. Infrared spectra of the composites showed that co-deposition did not alter the structure of the individual polymers. SEM micrographs of polypyrrole/polyaniline (PPy/PANi) composites showed uniformly deposited coatings with a compact platelet like morphology. The results obtained from DCP tests showed significantly improved corrosion performances for substrates coated with PPy/PANi composites.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:icps polypyrrole polyaniline pmaa corrosion evaluation
Date of Publication:01/01/2003