Adhesion of electrochemically formed polypyrrole coatings to low carbon steel

Abstract

AbstractThe lap shear strength of polypyrrole coatings formed on low carbon steel (∼ 23 MPa) is shown to be significantly higher (by ∼ 60%) than that obtained using uncoated steel as the adherend. The lap shear (adhesion) strength of polypyrrole‐coated steel varied with the pH of the monomer–electrolyte solution and the applied current. The low carbon steel‐containing polypyrrole coatings formed at low pH (pH ≤ 2.4) have higher adhesion strength than those coated with polypyrrole at higher pH (pH ≥ 6.0). However, poly(N‐methyl pyrrole)‐coated steel showed significantly lower adhesion strength. Increasing the applied current density decreased the adhesion strength. The surface free energies of polypyrrole coatings, ∼ 49–53 mJ/m2 are similar to that obtained for uncoated low carbon steel, ∼ 53 mJ/m2, indicating that polypyrrole will effectively wet low rbon steel. The extent of wetting of low carbon steel by the coatings was additionally confirmed by an interaction parameter, ϕ, of unity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2757–2763, 2002