Corrosion of conductive polypyrrole: Galvanic interactions between polypyrrole and metal substrates

• Galvanic interactions between polypyrrole and substrate metals were studied.
• Polypyrrole generally suffers continuous cathodic polarisation in the couples.
• Galvanic couples show unstable state with a poor passivated substrate metal.
• Polypyrrole accelerates the corrosion of metals in active dissolution state.

In deaerated or aerated 0.1 M NaCl (pH = 1 or 7), galvanic interactions between polypyrrole (PPy) films and different metals (13Cr, NiTi, Pt, Ti and Cu) were investigated in simulated galvanic couples. The PPy suffers cathodic polarisation while the substrate metals (apart from Pt) suffer anodic polarisation. When the substrate metal is inert or well passivated, such as Pt or Ti, there is no galvanic interaction between them. When the substrate metal is in a poor passivation or an active dissolution state, such as 13Cr, NiTi or Cu, the galvanic interactions between them may be strong and cannot be ignored.