Optimized Anticorrosion of Polypyrrole Coating by Inverted-Electrode Strategy: Experimental and Molecular Dynamics Investigations

Abstract

To improve the poor adhesion and the ensuing insufficient anticorrosion efficacy of electropolymerized polypyrrole (PPy) on copper surface, an inverted-electrode strategy was applied after the passivation procedure, for which the compact coating (PPy-I) was deposited on the substrate in a cathodic window. Morphological and physical characterizations revealed that PPy-I exerted satisfactory adhesion strength and suitable thickness and conductivity compared with the analogue prepared via the traditional protocol (PPy-T). Potentiodynamic polarization, electrochemical impedance spectroscopy and frequency modulation were employed to ascertain the propitious protection of PPy-I for copper in artificial seawater (ASW). Due to the dominant electroactivity, the PPy-I-coated sample possessed higher apparent current density and lower charge transfer resistance than its PPy-T-protected counterpart, which maintained the passivation of the substrate. Surface analysis also supported the viability of PPy-I for copper in ASW for a well-protected surface with inferior water wettability. Molecular dynamics simulations evidenced that PPy-I with the higher density retained efficient anticorrosion capacity on copper at elevated temperatures. Therein, the derived time-dependent spatial diffusion trajectories of ions were locally confined with low diffusion coefficients. Highly twisted pore passages and anodic protection behavior arising respectively from the tight coating architecture and electroactivity contributed to the adequate corrosion resistance of PPy-I-coated copper.

Double Stimuli-Responsive Conducting Polypyrrole Nanocapsules for Corrosion-Resistant Epoxy Coatings

“…In the epoxy-PPy coatings, the dominant electroactivity of the conducting PPy can maintain the passivation of the metals, and hence influence the corrosion rate of the underlying 304SS substrate. 51 After 3 h of immersion, the Nyquist plot of the epoxy-PPy coating shows a small depressed capacitive loop along with a straight line at low frequencies, indicating that the corrosion behavior model epoxy-PPy requires a finite-length Warburg impedance (Z d ) (Figure S5c). The finite-length diffusion accords with those of conducting polymers, reflecting the favorable conductivity of PPy nanocapsules and charge diffusion within the PPy chains.…”

“…Its corrosion resistance began declining after 480 h of immersion, indicating that its protection performance destabilizes during the long-term immersion periods in a 3.5 wt % NaCl solution. In the epoxy-PPy coatings, the dominant electroactivity of the conducting PPy can maintain the passivation of the metals, and hence influence the corrosion rate of the underlying 304SS substrate . After 3 h of immersion, the Nyquist plot of the epoxy-PPy coating shows a small depressed capacitive loop along with a straight line at low frequencies, indicating that the corrosion behavior model epoxy-PPy requires a finite-length Warburg impedance ( Z d ) (Figure S5c).…”

Nanocoating toward anti‐corrosion: A review

“…[26] Ozkazanc et al investigated the anti-corrosion behavior of PPy electropolymerized on a Cu electrode with the presence of different types of cations including NiCl2, FeCl2, ZnCl2, and CuCl2. [27] In another study, Ni-Ti alloy was found to be highly protected by thin films obtained from electrodeposition of PPy from mother solution of sodium bis(2-ethylhexyl) sulfosuccinate. [28] Interestingly, Ascencio et al found out that PPy film deposited on WE43 Mg alloy exhibited enhanced protective properties after every electrolyte renewal, which was associated with decoupling of substrate/coating resulted from misalignment of their Fermi levels.…”

“…investigated the anti‐corrosion behavior of PPy electropolymerized on a Cu electrode with the presence of different types of cations including NiCl 2 , FeCl 2 , ZnCl 2 , and CuCl 2 . [ 27 ] In another study, Ni‐Ti alloy was found to be highly protected by thin films obtained from electro‐deposition of PPy from mother solution of sodium bis(2‐ethylhexyl) sulfosuccinate. [ 28 ] Interestingly, Ascencio et al .…”

Layer‐by‐layer preparation of electromagnetic NH2‐SiO2/polypyrrole/Ni nanocomposites, characterization and their electrochemical properties

“…10,[21][22][23][24][25][26][27][28][29] Also, in some investigations PPy particles have been used as core particles for modification with polymer or inorganic nanoparticles. 6,14,[30][31][32][33] In this regard, mesoporous SiO 2 can be a good platform to host PPy and the modified composites are believed to possess improved physicochemical properties and hence would have broad application potential in areas like heterogeneous catalysis, 34,35 biomedicine, 36,37 separation techniques, [38][39][40] sensor science, 41 conductive paints, 42 anticorrosion coatings [43][44][45] and conductive pigments. 46 To further widen the application prospect in electrochemical sensors, biosensors, energy storage materials and catalysis, doping of conducting polymers with various nanomaterials, such as carbon, metals or metal oxides, has been attempted.…”