Coatings tailored to corrosion protection of metallic substrates are of the utmost relevance to ensure reliability and long-term performance of coated parts as well as the product value of the coated materials. Presently, there is a strong emphasis on the development of advanced functional and smart coatings for corrosion protection in different technological applications. On the one hand, there is a need for more advanced coatings for conventional applications and, on the other hand, there is a need to answer the requirements of several new Hi-Tech applications. Thus, this review highlights the most recent trends in the field of functional coatings for corrosion protection of metallic materials in a wide range of technical applications. Emphasis is given to self-healing coatings and smart coatings combining multiple functionalities for increased corrosion protection. Recent developments on the introduction of functionalities based on encapsulation of corrosion inhibitors, anti-fouling agents and superhydrophobic additives or modification of organic and hybrid matrices via chemical manipulation are reviewed. Special attention is dedicated to functional coatings for corrosion protection of bioresorbable metallic implants that have an important impact in biomedical applications.

Functional and smart coatings for corrosion protection: A review of recent advances

Self-healing mechanisms in smart protective coatings: A review

“Smart” coatings for active corrosion protection based on multi-functional micro and nanocontainers

Advances in functionalized polymer coatings on biodegradable magnesium alloys - A review.

Smart self-healing coatings for corrosion protection of metallic substrates (steel, magnesium, and aluminium, and their alloys) have attracted tremendous interest due to their capability to prevent crack propagation in the protective coatings by releasing active agents from micro/nanocapsules, that is, micro/nano particles consisting of a coating layer or a shell (micro/nanocontainers) and core material (solids, droplets of liquids or gases), in a controllable manner. This paper aims to give a concise review on the most recent advances in preparing micro/nanocapsules based on different types of micro/nanocontainers, i.e., organic polymer coatings, inorganic clays, mesoporous silica nanoparticles, polyelectrolyte multilayers, etc. for smart coatings with self-healing properties. The state-of-the-art design and preparation of micro/nanocapsules are highlighted with detailed examples.

Advanced micro/nanocapsules for self-healing smart anticorrosion coatings

Zn-Al layered double hydroxides as chloride nanotraps in active protective coatings

Coffee-derived activated carbon from second biowaste for supercapacitor applications.

Smart epoxy coatings modified with different additives were applied on AA2024. The following three different systems were studied: a reference consisting of an epoxy coating containing chromate active pigments and two “smart” coatings modified with containers loaded with corrosion inhibitor—layered double hydroxides filled with mercaptobenzothiazole and tubular halloysites (HS) filled with 8-hydroxyquinoline. The thickness of the coatings was determined by scanning electron microscopy. The barrier properties and the average corrosion resistance were assessed by electrochemical impedance spectroscopy (EIS). The long-term corrosion repair ability of the various coatings was confirmed by EIS measurements carried for a period of 3 weeks in scratched samples. The ability of the smart additives to inhibit corrosion over defects with different sizes and geometry was studied at the microscale by using localized impedance spectroscopy (LEIS) and the scanning vibrating electrode technique. The results demonstrate that the additives provide effective corrosion inhibition on defects of various sizes. Moreover, the LEIS measurements give some important highlights concerning the mechanisms and kinetics of inhibition of each system.

Electrochemical study of the corrosion inhibition ability of “smart” coatings applied on AA2024

Bi-layered functional coatings were developed to modify the surface of AZ31 and ZE41 Mg alloys intended as biodegradable implant materials for bone repair applications. An inner silane-TiO2 coating was designed to slow down the degradation rate of Mg alloys while a top-most biopolymer layer, composed of collagen or chitosan, was intended to improve bioactivity and biocompatibility of the alloys. Scanning vibrating electrode technique (SVET) and scanning ion-selective technique (SIET) were used to study the localized corrosion phenomena and localized pH evolution of silane-TiO2 coated Mg alloys. Electrochemical impedance spectroscopy (EIS) evaluation of bi-layered alloys in simulated body fluid (SBF) showed that the presence of the biopolymers promotes formation of carbonated compounds within the corrosion products. Localized electrochemical impedance spectroscopy (LEIS) results revealed that the top-most biopolymer layers do not have a detrimental effect on the barrier properties of the silane-TiO2 coating. Indeed, formation of gas pockets evidenced that collagen and chitosan layers trap evolved H2 avoiding its release into the solution at early stages of immersion. The here reported results contribute to elucidate the corrosion mechanisms of AZ31 and ZE41 Mg alloys on the long term in a biological context and provide promising insights into their control via a multilayered coatings.

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Hybrid coatings with collagen and chitosan for improved bioactivity of Mg alloys

Thin films of W–Si–N, deposited by reactive magnetron sputtering, were investigated using X-ray photoelectron spectroscopy (XPS). The objective of this research work was to study the chemical binding state of these coatings. During the sputtering process, the established atomic bonds may possibly not agree to the elemental bonding preview using the values of chemical affinity, which decrease for SiN, SiW to WN bonds. XPS data show that in W-based films which have simultaneous additions of Si and N, a SiN type is the preferential bond established. This behaviour is confirmed either by the evolution of the Si/W atomic ratio of the as-deposited coatings, which increase with the N content, or the variation of the lattice parameters of the b.c.c. α-W phase for W–N, W–Si and W–Si–N systems. However, since no compound of silicon nitride was detected, it was concluded that this phase, formed by specific contents of Si and N must have been present in the W–Si–N films in the amorphous state.

http://gecea.ist.utl.pt/Publications/FM/2001-02.pdf

Fatima Montemor

Papers

Zn-Al layered double hydroxides as chloride nanotraps in active protective coatings

Coffee-derived activated carbon from second biowaste for supercapacitor applications.

Electrochemical study of the corrosion inhibition ability of “smart” coatings applied on AA2024

Hybrid coatings with collagen and chitosan for improved bioactivity of Mg alloys

How is the chemical bonding of W-Si-N sputtered coatings?