Morphology and structure of the passive interphase formed during aqueous electrodeposition of polypyrrole coatings on steel

An iron(II) oxalate dihydrate passive interphase was electrodeposited on st eel substrate from aqueous oxalate solutions prior to the electrochemical p olymerization of pyrrole. The effect of electrochemical process parameters on the morphology and structure of the passive interphase was systematicall y investigated by scanning electron microscopy(SEM) and X-ray diffractometr y (XRD). Our results reveal that the passive interphase is composed of a mo nolayer of closely packed crystals. The size of the crystals is dependent o n the experimental conditions. The iron(II) oxalate dihydrate interphase fo rmed on steel by electrochemical deposition has an orthorhombic structure i rrespective of the reaction condition. The unit cell dimensions of the pass ive interphase formed by electrodeposition are slightly different from thos e formed by conventional chemical process. (C) 1999 Elsevier Science Ltd. A ll rights reserved.