Formation of Corrosion Resistant Organic Polymer Coatings by an Electrochemical Process
Abstract
This project dealt with the formation, characterization and properties of corrosion resistant polypyrrole and substituted polypyrrole coatings. Aqueous electropolymerization was used to apply polypyrrole coatings onto low carbon steel (99.9% (Fe), 0.1% C). Galvanostatic electropolymerization was used throughout the course of this project. The progress of electropolymerization was followed by tracing the potential time (E-t) curve as a function of the reaction variables. Aqueous electropolymerization of pyrrole and methylpyrrole occurred instantaneously in basic medium (pH >/= 8.4). However, three distinct reactions occurred in acidic medium (pH </= 6.0). These reactions were identified as the oxidation of steel, passivation of steel and polymerization. Polymerization commenced after steel was completely covered by the passive coatings. The transition of steel from a reactive substrate to a passive substrate is marked by the change in the electrode potential from negative values (approx. -0.44 vs SCE) to positive values > 0.65 vs SCE. The passivation time decreased with increased applied current. In acidic medium, the passivation time was minimum at pH 2.4. The adhesion strength of the polypyrrole coated steel was determined to be about 56% higher than that for uncoated steel. The adhesion strength varied with the electrochemical process parameters. Low pH and low current densities produced coatings with highest adhesion strength approx. 23 MPa. The corrosion rate of the polypyrrole coated steel was shown to be very low 2.9 - 0.16 mpy compared to that for the control of about 41.36 mpy.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 24, 1999
- Accession Number
- ADA366230
Entities
People
- Jude O. Iroh
- Wencheng Su
Organizations
- University of Cincinnati