Long‐Term Active Corrosion Protection of Damaged Coated‐AA2024‐T3 by Embedded Electrospun Inhibiting Nanonetworks

Abstract

the inhibitor from the matrix so unwanted reactions do not take place; and (ii) allow for the controlled release of the inhibitor (controlled kinetics or on-demand release). Many materials, shapes, sizes, and triggers have been developed using this basic principle ranging from microcapsules and nanocapsules relying on delamination to initiate the redox triggered release, to loaded nanosized porous zeolites and halloysite nanotubes where release relies on leaching and ion exchange. [1] Despite the clear success of the concept, two intrinsic limitations can be identified: (i) loading in nanoparticles is limited and bound to carrier-inhibitor pairs; and (ii) inhibitor release at a damage site greatly depends on particle size, release trigger, loading, and distribution. [2] As a consequence the long-term protection and protection at relatively big damages is compromised. [2b] Here we propose an alternative strategy based on the formation of low-density and/or humidity responsive interconnected paths of inhibitor inside the coating (i.e., inhibiting nanonetworks) as a way to overcome the above limitations. Such a strategy is based on recent findings by Hughes et al. [3] who recently attributed high inhibition of Cr(VI)-based coatings to the formation of inhibitor interconnected clusters and low density regions in the coating, thereby confirming previous modelling works. [2] In order to experimentally proof the validity of the concept we used the well-established process of electrospinning as the method to manufacture the responsive nanofiber mats containing corrosion inhibitors to form the inhibiting nano networks in the coatings. During the relatively simple process of electrospinning a membrane or fiber mat of polymeric fibers can be produced by applying an electric field between a spinneret, usually a needle of a syringe filled with polymer solution, and a grounded conductive collector. [4] By controlling the process parameters, spinning setup complexity, and the polymer solution physical properties, a large amount of geometries can be designed making it a suitable process for the design of membranes, drug delivery systems, and carriers of liquid self-healing agents for composites among others. [5] Cu-rich aluminum alloy AA2024-T3 is here used as the substrate to prove the corrosion inhibiting potential of the concept. This highly used aerospace grade aluminum alloy is known for its high corrosion In this work, a new concept is introduced for active corrosion protection at damaged sites aiming at overcoming existing limitations of currently proposed strategies based on dispersed inhibitor-loaded nanocontainers in coatings. The underlying principle is based on the formation of lowdensity and/or humidity responsive interconnected paths of inhibitor in the coating, what is called inhibiting nanonetworks. Such an approach allows for (on-demand) long-term local supply of corrosion inhibitor at the damage site.For the proof-of-concept, water responsive inhibiting nanonetworks based on polyvinyl alcohol and two known...

Electrospinning: A Powerful Tool to Improve the Corrosion Resistance of Metallic Surfaces Using Nanofibrous Coatings

“…A self-healing effect has been observed in the sample doped with cerium acetylacetone, providing a significant recovery of the corrosion resistance due to the formation of cerium hydroxide on the defective zone. The same PVA precursor was used by [65] to obtain long-term active corrosion protection of damaged coated aluminium alloy by embedded electrospun inhibiting nanonetworks. In this work two corrosion inhibitors such as cerium chloride and lithium carbonate have been used.…”

“…Tafel polarization curves, immersion test and weight loss in SBF [46] PCL/HA-NPs/simvastatin Magnesium alloy (AZ31) Tafel polarization curves and Electrochemical Impedance Spectroscopy (EIS) [47] PANI/PMMA Q325 carbon steel Tafel polarization curves and Electrochemical Impedance Spectroscopy (EIS) [48] PANI/PMMA Q235 carbon steel Tafel polarization curves and Electrochemical Impedance Spectroscopy (EIS) [49] PANI/PMMA (primer) and PS (topcoat) Q235 carbon steel Tafel polarization curves and Electrochemical Impedance Spectroscopy (EIS) [50] PAN-Al 2 O 3 Zinc sheet Hydrogen evolution, Tafel polarization curves and Electrochemical Impedance Spectroscopy (EIS) [51] PVA/glyoxal Aluminium alloy (AA6082) Electrochemical Impedance Spectroscopy (EIS) [52] PVDF/SA Aluminium sheets Tafel polarization curves and Electrochemical Impedance Spectroscopy (EIS) [55] PANI-PFOA/PS Q235 carbon steel Tafel polarization curves and Electrochemical Impedance Spectroscopy (EIS) [56] PVC PS Brass Cyclic potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) [57] PVC Aluminium, copper and brass Cyclic potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) [58] PVA PVC Aluminium Cyclic potentiodynamic polarization and Electrochemical Impedance Spectroscopy (EIS) [59] PS Aluminium Potentiodynamic polarization curves [60] PS/Al 2 O 3 Commercial aluminium foil Electrochemical Impedance Spectroscopy (EIS) [61] PS/mod-SiO 2 Magnesium alloy (AZ31) Potentiodynamic polarization curves [62] (PFDA-co-AA)-b-PAN) Aluminium alloy (AA2024T3) Acetic acid salt spray test [63] PVA/glyoxal doped with cerium nitrate and cerium acetylacetone Aluminium alloy (AA6082) Electrochemical Impedance Spectroscopy (EIS) [64] PVA/GA doped with CeCl 3 and Li 2 CO 3 Aluminium alloy (AA2024-T3) Electrochemical Impedance Spectroscopy (EIS) [65]…”

A Comparative Study of Multifunctional Coatings Based on Electrospun Fibers with Incorporated ZnO Nanoparticles

“…More recent research has been based on the immobilization of corrosion inhibitors into the electrospun fibers for improving the corrosion resistance. In this sense, the electrospun fibers act as ideal hosts of a wide variety of corrosion inhibitors of different nature such as cerium chloride, lithium carbonate, 2-mercaptobenzothiazole or even metal oxide nanoparticles (TiO 2 , ZnO) [23][24][25][26]. In addition, the presence of this type of nanoparticles between the interstices of the electrospun fibers can increase the surface roughness as well as the air entrapment, and as a result, an important increase in the water repellent behavior and, thus, a considerable enhancement in the corrosion resistance is obtained.…”

Controlling Release Kinetics of Payloads from Polymer Conjugates by Hydrophobicity

“…Corrosion inhibitors can be incorporated in active layers by directly mixing inhibitors with coating components, encapsulation of corrosion inhibitors in nanoparticles, micro/nanocapsules, nanofibers, and conjugation of corrosion inhibitor via labile or non‐labile bonds to polymers coatings . Conjugation of corrosion inhibitors to polymer structures via stimuli‐cleavable linkages allow sustained release of corrosion inhibitors upon changes of environments due to corrosion, such as change of pH value or electrochemical potential.…”