Novel zinc‐rich epoxy paint coatings with hydrated alumina and carbon nanotubes supported polypyrrole for corrosion protection of low carbon steel: Part I: Inhibitor particles and their dispersions

Abstract

In part 1 of this work, preparation, structure, spectroscopic, and electrochemical characteristics of the polypyrrole (PPy) deposited alumina/multi-walled carbon nanotubes (MWCNTs) inhibitor particles (PDAMIPs) are presented. TEM observations evidenced uniform deposition of thin PPy film on the functionalized nanotubes, whereas co-deposition of PPy and polystyrene sulfonic acid (PSS) lead to thick polymer coverage on hydrated alumina. Modification with polymer complexes resulted in moderately dispersed PDAMIPs, which is due to the various degrees of aggregation and coalescence. FTIR revealed compact and dense PPy structure on the functionalized MWCNTs while it was not the case on alumina and the PSS modified nanotubes. Closer interaction of PPy with the MWCNTs resulted in enhanced charge mobility, whereas greater electroactivity and reversibility of PPy were noted to samples containing functionalized nanotubes and low amount of PSS. Rheological study verified moderate micron-scale dispersity and the modification caused various degrees of aggregations of the PDAMIPs. These were recognized to be valid in the suspensions at a solid phase concentration with component contents similar to the corrosion tested hybrid coatings. Rheological percolation of the nanotubes (with anisotropic factor of $100) was confirmed at volume fractions of 3.30 Â 10 À3 and 6.0 Â 10 À4 which were under the dilute/ semi-dilute boundary type theoretical and experimental thresholds.This is related to the extensive interconnection of the nanotube-supported filaments. Thus, overlapping of the nanotubes should contribute to the electrical percolation thereby galvanic corrosion prevention function of the zinc-rich hybrid coatings, which is discussed in the 2nd part.

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

“…Besides altered hydrophilicity, high impedance moduli are associated with high pore resistance in all cases partly as a result of moderate and low density spatial interconnections of the nanotube filaments in the p1 and the p2–p4 particles based paint dispersions, respectively. Varied connection densities of the nanotubes supporting PPy networks should obviously contribute to galvanic function of the hybrids, which is concluded based on electrochemical and rheology characterization (detailed in 1st part of this work 19). The coatings with low sulfonated nanotubes at 1 and 3 wt% did not provide valuable corrosion prevention.…”

“…Hence, PDAMIPs obviously contribute to low intensity and efficient galvanic function of the hybrids with closed structure of zinc encased by the epoxy (no porosity at 25.7% by volume). Low nanotube contents in the H3 is emphasized by the fact that entanglement regime was not experienced by rheology characterization (1st part of this study 19). In addition, electrical contacts between zinc pigments should be influenced by the high proportion of alumina supported PPy whose concentration was around the percolation threshold in PDAMIPs 37.…”

“…Conducting paths without macroscopic electrical percolation (below threshold) may exist in multi‐phase composites of the ICPs 42. Therefore, due to the similar reversibility and charging efficiency, different nano‐ and micro‐structure (characterized in Part I 19) as well as permeability of the PDAMIPs are attributed to the much varied protection characteristic of the zinc‐rich hybrids. In the light of usually not overlapping electrical and rheological percolation ranges, that is, electrical percolation is more sensitive to network of the nanotubes than force dissipation related flow properties 43, 44, since PDAMIPs must facilitate steel protection when density of the particles and extent of interactions entail in the onset of electrical percolation.…”

“…Scribes were made by a blade as X‐cuts. Composition of the PDAMIPs is given in Table 1 (preparation details in Part 1 19) whereas Table 2 summarizes the composition of paint coatings.…”

“…Owing to the fact that nanotubes deteriorate corrosion resistivity of metals 15–18, the scope of the study is to clarify application premises and present proper use of the nanotubes. In this part, corrosion prevention of zinc‐rich hybrid paints is investigated and discussed in the light of properties, structure, and distribution of the inhibitor particles characterized in 1st part of this study 19.…”