Novel zinc-rich epoxy paint coatings with hydrated alumina and carbon nanotubes supported polypyrrole for corrosion protection of low carbon steel: Part II: Corrosion prevention behavior of the hybrid paint coatings

摘要

Utilization of various types of multi-walled carbon nanotubes (MWCNTs) in zincrich paints (ZRPs) is presented addressing percolation and porosity related phenomena of traditional ZRPs. Hybrid paint coatings were formulated with 3.21 wt% polypyrrole (PPy) deposited alumina-MWCNT inhibitor particles (PDAMIPs) and 70 wt% zinc contents. Corrosion protection behavior of the hybrid coatings was investigated by electrochemical impedance spectroscopy (EIS), glow-discharge optical emission spectroscopy (GD OES), X-ray photoelectron spectroscopy (XPS), and FT-Raman spectroscopy. Immersion and salt-spray chamber tests gave evidence of improved galvanic protection and barrier nature of the hybrid coatings over the conventional ZRPs, whereas inhibited zinc corrosion and ignorable steel corrosion took place besides lower degradation of the binder. Zinc-rich hybrid paints with either high relative amount of polyelectrolyte-modified or low proportion of functionalized MWCNTs afforded enhanced corrosion prevention. This result is partly attributed to the nanotube volume fractions around the threshold of infinite cluster formation contributing to electrical percolation and galvanic action of the hybrids. Experimental results are discussed in a broader context on the basis of structure related findings of the PDAMIPs (described in Part I) and in the light of recent literature data. From the newly developed inhibitor particles, some of them are respected as worthy additives for application in hybrid coatings featuring high performance corrosion prevention functionality.