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Active anodic zinc content below 90 wt.% does not support sufficient electrical contacts but higher contents cause high porosity of traditional liquid zinc-rich paints (ZRPs). To resolve this problem, our proposal is the application of highly dispersed polypyrrole (PPy) coated alumina inhibitor particles (PCAIPs) in zinc-rich paint compositions. Using these nano-size inhibitor particles at concentrations from 4.55 to 0.85 wt.%, hybrid paints were formulated with zinc contents ranging from 60 to 85 wt.% at the same time. Submicron morphology and nano-scale structure, spectroscopy characteristics and electrochemical properties of the PCAIPs were studied by transmission electron microscopy (TEM) and rheology, Fourier-transform infrared spectroscopy (FT-IR) and cyclic voltammetry (CV) in first part of the work. In the second part, electrolytic corrosion resistivity of two sets of paint coatings were salt-spray chamber and immersion tested with 5 wt.% aqueous solution of sodium chloride. Active corrosion prevention ability of the saltspray tested coatings was evaluated in compliance with ISO recommendations. Dielectric properties of the coatings during the immersion tests were monitored by electrochemical impedance spectroscopy (EIS). Corrosion tested area of the coatings was investigated by glowdischarge optical emission spectroscopy (GD-OES) to disclose infiltration of corrosive analytes and oxygen enrichment in the cross-section of the primers in comparison with their pristine states. Morphology of the zinc pigments was examined by scanning electron microscopy (SEM), and quality of steel specimens and the interfacial binder residues by X-ray photoelectron spectroscopy (XPS) as well as FT-Raman and Mössbauer spectroscopy. The results of both types of corrosion tests evidenced efficient utilisation of sacrificial anodic current for galvanic protection and improved barrier profile of the hybrid coatings, along with the PCAIP inhibited moderate selfcorrosion of zinc. As a result of well balanced active/passive function, the hybrid coating 2 containing zinc at 80 wt.% and PCAIPs at 1.75 wt.% embedding PPy at 0.056 wt.% indicated the most advanced corrosion prevention. Galvanic function of the hybrid paints is interpreted on the basis of size-range effect and spatial distribution of the alumina supported PPy inhibitor particles and basic electrical percolation model considerations.

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In this review, most of the works are attempted to cover about corrosion protection of metals with molecular-tight atomic thin carbon layers of all sorts of graphene derivatives from the very beginning to the latest theoretical and experimental research findings, so as engineering achievements in the field up to date. Although high and tuneable electrical conductivity of graphene is the main feature exploited in majority of the applications such as catalysis, photocatalysis, electrocatalysis, low electrical but high chemical resistivity electrodes in batteries, and ultracapacitors, corrosion protection of metals favours the opposite – good physical separation and electrical insulation. Both of the latter ones lead to durable excellent protection, which can only be ensured by special design and implementation. Thus, the milestones of major hardships both on theoretical and practical sides are delineated similarly as utmost developments in circumventing all problems with an aim to ensure timely transfer from the research phase to successful industry utilisations. Relying on numerous works, this paper gives a comprehensive overview in the subjects of preparation, modification, and use of multiple sorts of graphene in the forms of neat, combined layers, and composite coatings on numerous metals. All performance parameters are given in detail. Chronological order of the article serves the purpose to give the reader a clear picture and an important clue on viability of strategies in the aspects of environmental friendliness, attainable maximum durability, and performance of corrosion protection with graphene films, as well as further advancements in the field expected to occur in the near future.

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.