Corrosion Communications 1 (2021) 18–25
Contents lists available at ScienceDirect
Corrosion Communications
journal homepage: www.elsevier.com/locate/corcom
Review
Self-healing corrosion protective coatings based on micro/nanocarriers: A
review
Tong Liu a, Lingwei Ma a,b, Xin Wang a, Jinke Wang a, Hongchang Qian a,b, Dawei Zhang a,b,∗,
Xiaogang Li a,b
a
National Materials Corrosion and Protection Data Center, Institute for Advanced Materials and Technology, University of Science and Technology Beijing, Beijing
100083, China
b
BRI Southeast Asia Network for Corrosion and Protection (MOE), Shunde Graduate School of University of Science and Technology Beijing, Foshan 528399, China
a r t i c l e
i n f o
Article history:
Received 26 May 2020
Received in revised form 11 July 2020
Accepted 15 July 2020
Available online 4 June 2021
Keywords:
Corrosion protection
Organic coating
Self-healing material
Micro/nanocarrier
a b s t r a c t
Extrinsic self-healing corrosion protective coatings have attracted substantial interest because of their ability to
prevent damage propagation by releasing corrosion inhibitors and polymerizable agents from micro/nanocarriers.
Various micro/nanoencapsulation technologies have been adopted to optimize the loading capacity and to control
the releasing behavior of the healing agents for enhancing the self-healing functionality. This study aims to
review recent advances in self-healing corrosion protective coatings based on micro/nanocarriers. This review
also provides insights for the further development of extrinsic self-healing coatings by evaluating the advantages
and limitations of different healing systems.
© 2021 The Authors. Published by Elsevier B.V. on behalf of Institute of Metal Research, Chinese Academy of
Sciences.
This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
1. Introduction
Corrosion is a widely occurring phenomenon in natural and industrial environments and can severely deteriorate the properties of metals
during their service lives. Recent studies have revealed that the total
global annual cost of corrosion may approach 2.5–4.0 trillion dollars
[1,2]. Of the numerous corrosion protective techniques, organic coatings are the most commonly used, and their cost is as high as two-thirds
of the total corrosion protection expenditure [3]. However, traditional
organic coatings are susceptible to various types of damage, such as microcracks, pinholes, cavities, mechanical scrapes and scratches during
transportation and service applications. Thus, to maintain the protective
effects, particularly when used in harsh corrosive environments, organic
coatings often require frequent repair and replacements. The concept of
self-healing coatings was first proposed in the 1980s to reduce the frequency of repairs and the associated costs [4], yet it remains an active
research topic in the corrosion community. These coatings exhibit outstanding performance and enhance the long-term corrosion protection
of the materials to which they are applied [5-8].
In corrosion protective coatings, self-healing actions can be achieved
by intrinsic or extrinsic healing mechanisms, or both. Intrinsic selfhealing is based on the unique molecular architecture of the coatings,
and thus, does not require an external component to be embedded. Un-
∗
der external stimuli such as light, chemicals, temperature or humidity
changes, the original performance of the damaged coatings can be recovered by reversible reactions via the Diels–Alder reaction [9,10], disulfide
bond [11], trithiocarbonate reshuffling reaction [12], hydrogen bond
[13,14] or dynamic urea bond [15]. The major advantages of the intrinsic self-healing coatings include their ability to restore the barrier
properties, even after multiple damage-healing cycles. However, the required reversible reactions are dependent on specific functional groups
and their synthesis can be prohibitively expensive and extremely complicated for industrial applications. In contrast, the repair process of
the extrinsic self-healing coatings can be conveniently accomplished by
the release of conveyed healing agents such as polymerizable materials and corrosion inhibitors to the damaged area of the coating. The
healing agents are mainly stored in micro/nanocarriers or microvascular networks, which essentially reduce undesirable interactions with
the bulk coating and also facilitate on-demand and controllable release
[16]. The micro/nanocarriers are often designed to release the encapsulated healing agents in response to environmental changes and hence
actively recover the protection performance of the coating. Additionally, infiltrating the coating with a microvascular network may effectively increase the coverage of healing agents compared with that of micro/nanocarriers. However, this approach introduces the potential risk
of creating more interfacial defects as conduits for water penetration
Corresponding author.
E-mail address: dzhang@ustb.edu.cn (D. Zhang).
https://doi.org/10.1016/j.corcom.2021.05.004
2667-2669/© 2021 The Authors. Published by Elsevier B.V. on behalf of Institute of Metal Research, Chinese Academy of Sciences. This is an open access article
under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
T. Liu, L. Ma, X. Wang et al.
Corrosion Communications 1 (2021) 18–25
Fig. 1. Schematic representation of the synthesis of microcapsules using in situ polymerization.
that can lower the barrier properties of the coating matrix; therefore,
this method is less reported for corrosion protection applications.
With the rapid development of self-healing coating systems, many
new strategies have been proposed [17-22]. This paper aims to provide
an updated review to summarize the most recent trends in the diversifying micro/nanocarriers employed for self-healing corrosion protective
coatings.
place rapidly at the aqueous or organic interface, thereby producing micro/nanocapsules with the healing agent or inhibitor as the core. This
capsulation technique has many advantages, such as (1) mild reaction
conditions, (2) fast encapsulation, (3) high encapsulation efficiency, and
(4) controllable capsule size (3–30 𝜇m) [24,25]. However, the prepared
capsules generally contain unpolymerized shell monomers, which may
react with the core material, thereby impacting the performance of the
microcapsule.
2. Micro/nanoencapsulation techniques
2.3. Pickering emulsion polymerization
Micro/nanocarriers can be prepared using different physical or
chemical approaches. The physical procedures include solvent evaporation, spray drying, centrifugal extrusion, the spinning disk method,
and fluid bed coating. The chemical approaches include in situ polymerization, interfacial polymerization, centrifugal force approaches, submerged nozzle processes, and phase separation [17]. The structure and
properties of the micro/nanocarriers play important roles in determining the performance of the extrinsic self-healing coatings. Generally, the
as-prepared micro/nanocarriers should possess (1) appropriate chemical and mechanical stability, (2) high loading capacity, (3) compatibility with the coating resin, (4) appropriate size and structure, (5)
ability to sense damage or corrosion, and (6) release behaviors tuned
in with damage development [18]. Reliable micro/nanoencapsulation
techniques, such as in situ polymerization, interfacial polymerization,
Pickering emulsion polymerization, sol-gel reaction technique, solvent
evaporation, and the other advanced encapsulation methods, that can
satisfy these performance requirements, are briefly described in the subsequent sections. The involved micro/nanocarriers are categorized as
micro/nanocapsules, micro/nanocontainers, or other inhibitor hosts.
The term Pickering emulsion was first established by S.U. Pickering in 1907 [26]. However, it was not until 1996 that Velev et al.
[27] demonstrated the potential of this method as an encapsulation
method. Generally, the Pickering emulsion polymerization technique
contains two steps: (1) preparation of a Pickering emulsion and (2) encapsulation of the core material. In short, the colloidal particles are first
assembled at the water/oil interface by mechanical action to form a
stable Pickering emulsion. Next, the colloidal particles are cross-linked
through a chemical reaction to form a compact shell wall. In contrast to
traditional surfactant-based emulsions, the Pickering emulsion has several desirable features, such as high stability (suppression of droplets
coalescence), low toxicity, low cost, and reusability, making it an excellent candidate for microencapsulation. In addition, many colloidal
particles can be utilized as shell materials with polymer microspheres
and inorganic micro/nanoparticles. Moreover, the mechanical performance of the shell can be regulated by adjusting the particle size and
immobilization method. At the same time, it should be noted that the
permeability of the shell wall can also be easily controlled by adjusting
the size of the voids between the colloidal particles [17], which may
suggest a controlled-release mechanism for the microcapsules.
2.1. In situ polymerization
In situ polymerization is the most common method for the encapsulation of core materials, and possesses many advantages, e.g., simple
operation, controllable capsule size and shell thickness, low cost, and
suitability for upscale production. However, compared to other encapsulation approaches, this technique requires a longer reaction time, usually several hours. For example, microcapsules containing dicyclopentadiene (DCPD) monomers were prepared using in situ polymerization
of poly(urea-formaldehyde) (PUF) as the shell material [23]. A typical
preparation process of the microcapsules is depicted in Fig. 1. The obtained microcapsules had average diameters ranging from 10–1000 𝜇m,
which were adjusted by varying the agitation speed between 200 and
2000 r/min, and the shell thickness was controlled at 160–220 nm.
2.4. Solvent evaporation
In the solvent evaporation method, the shell material is first dissolved in a water-insoluble volatile solvent, such as dichloromethane.
The core substance is then dispersed or dissolved in the solution obtained. Subsequently, the solution is slowly added to an aqueous solution containing a stabilizer, such as poly(vinyl alcohol) (PVA), and
further stirred to form micro-sized polymer droplets containing the core
substance. The process of hardening of the shell wall is accomplished
after the removal of the volatile solvent from the polymer droplets, often at elevated temperatures or under reduced pressures. Therefore, as
the stirring proceeds, the polymer droplets gradually harden to form
the final micro/nanocapsules. Unlike other encapsulation methods, the
solvent evaporation method involves very simple and mild preparation conditions [17]. However, during the solvent evaporation process,
many parameters (such as monomer concentration, dispersion rate, and
core/shell ratio) must be carefully considered and controlled. A comprehensive understanding of the interdependency among these parameters
is required to precisely tailor the capsule size, shell thickness, shell compactness, and yield. Moreover, this technique is more feasible for solid
core materials than for liquids [19].
2.2. Interfacial polymerization
Interfacial polymerization is another extensively used method to encapsulate healing agents. During interfacial polymerization, the shell
prepolymers are dissolved in the core material (i.e., healing agent or
corrosion inhibitor), and then this mixture is mixed with the aqueous phase. Another polymerizable monomer or curing agent is added
to the mixed-phase. Subsequently, the polymerization reaction takes
19
T. Liu, L. Ma, X. Wang et al.
Corrosion Communications 1 (2021) 18–25
3. Coatings with micro/nanocarriers containing polymerizable
agents
2.5. Sol-gel reaction
The sol-gel technique is the main method for preparing inorganic
micro/nanocarriers under mild conditions. In self-healing materials,
sol-gel chemistry has been mainly used to prepare silica-based micro/nanocontainers, because silica shells can offer an effective barrier
for maintaining the chemical activity of the healing agents. In a typical sol-gel method, the organic components are first dispersed in an
aqueous phase. Then, the emulsified droplets are obtained using either
a vigorous agitation or a suitable surfactant/emulsifier. The emulsified
droplets function as a micro reactor and provide suitable conditions
for the reaction of the silicon-based monomers, eventually leading to
the formation of a suspension containing sol particles. Using the solgel method, the oil, aqueous solution and solid-phase particles can all
be encapsulated into the silica containers. However, it is worth noting
that micro defects (pores and cracks) may form on the shell of the containers after drying. In addition, this strategy is usually used to prepare nanoscale containers, which greatly limits the loading capacity
(~10 wt%) of the healing agent, leading to difficulty in repairing large
damages [19]. Based on the sol-gel reaction, Stöber and his coworkers
proposed a method for preparing solid silica microspheres by hydrolytic
condensation of tetraethoxysilane (TEOS) under alkaline reaction conditions [28]. This method has been widely used and modified to fabricate
mesoporous silica or other inorganic (e.g. TiO2 ) hollow spheres as micro/nanocontainers.
In 2001, the first study that introduced microcapsules to obtain a
self-healing polymeric composite was reported by White et al. [50]. This
work was fundamental and became one of the important references for
the synthesis of various micro/nanocapsules for self-healing materials.
In this study, DCPD monomers were encapsulated in urea-formaldehyde
(UF) microcapsules with an outer diameter of ~220 𝜇m by in-situ polymerization and the Grubbs catalyst was uniformly dispersed in the polymer matrix without further encapsulation. When a microcrack formed in
this composite, it directly led to the rupture of the microcapsules. Next,
liquid DCPD was released from the broken microcapsules, which subsequently flowed out and filled the damaged area. DCPD came in contact
with the pre-embedded Grubbs’ catalyst in the polymer matrix, initiating a ring-opening metathesis polymerization reaction, which caused
the formation of a cross-linked network to seal the damage. The same
strategy was later demonstrated in the development of numerous selfhealing corrosion protective coatings [25,51].
Typically, healing agents released from ruptured capsules should
preferentially possess mechanical strengths and chemical compositions
similar to those of the polymeric coating. As a result, an epoxy resin
with a composition similar to that of the coating matrix can be an appropriate option, owing to its excellent adhesion, mechanical strength
and chemical stability [52-54]. However, even when the healing agent
has the same composition as that of the coating matrix, it still cannot
completely restore the mechanical properties of the damaged coating
to the original state. Therefore, a self-healing polymer system with a
self-reinforcing effect is more attractive than traditional self-healing approaches. Weder et al. [55] implanted plasticizer-filled microcapsules
into a rigid and brittle polymer matrix to prepare a self-toughening
thermoplastic polymer. This strategy was demonstrated in a polymeric
composite comprised of a poly(lactic acid) (PLA) matrix and poly(ureaformaldehyde) microcapsules storing a hexyl acetate plasticizer. Based
on their results, although the PLA composite demonstrated brittle damage at a strain of ~2.5%, the self-toughening effect was triggered in
this condition because of the rupture of the microcapsules to release the
plasticizer. This effect led to a 20-fold increase in the toughness and a
25-fold increase in the elongation at break, compared with that of the
pure PLA.
Coatings with separate storage of polymerizable agents and catalysts in different microcapsules prevent premature interaction of the
two reagents and preserve the shelf life of the self-healing ability. However, in the coating matrix, the uneven dispersion of these two capsules
makes it difficult to achieve uniform mixing of the healing and curing
agents; and, at the same time, curing in the expected ratio is also an
issue. To overcome this challenge, liquid isocyanates have been used
as one-component polymerizable agents for self-healing materials [5658]. Isocyanates can react with moisture to form a polymeric shield,
making them ideal candidates as healing agents for corrosion protection applications. However, due to the high reactivity of isocyanates
[52], the microcapsules must be engineered with enhanced stability to
facilitate long-term storage [59,60]. For example, Wu et al. [59] prepared a silica/polyurea microcapsule for a hexamethylene diisocyanate
(HDI) healing agent using interfacial polymerization and a sol-gel process (Fig. 2). The results showed that this special encapsulation method
not only enabled the encapsulation of the isocyanate-based active agent
(liquid HDI) but also provided an enhancement in the chemical and
thermal performances of the capsules. The obtained silica/polyurea microcapsules exhibited only 5% mass loss when heated to 144 °C, which
was ~58 °C higher than that of pure polyurea microcapsules. The composite microcapsules were also more resistant to organic solvents such
as xylene, showing less than ~26 wt% decrease of the core content after
100 h of immersion.
Dry oils such as linseed or Tung oils solidify when they react with
oxygen and have also been used as polymerizable agents for self-healing
2.6. Precipitation-based methods
Among the methods summarized above, polymerization-based and
solvent evaporation methods are used to produce organic capsules,
whereas sol-gel methods are mostly dedicated to the preparation of inorganic silica micro/nanocarriers. In addition to these methods, a variety
of inorganic micro/nanocarriers can be conveniently prepared by precipitating them from aqueous or organic solutions. Herein, layer-double
hydroxides (LDHs) and zeolitic imidazole frameworks (ZIFs) are introduced as two types of inhibitor hosts.
LDHs are a group of lamellar ionic compounds consisting of positively charged layers with an interlayer region containing solvation
molecules and charge compensating anions [29]. An LDH is most commonly prepared by the co-precipitation of divalent and trivalent metal
salts in an appropriate ratio in an alkaline solution containing the target anions. LDH structures are aged at specific elevated temperatures to
improve the crystallization [30]. The high interlayer spacing and high
anion exchange capacities allow LDHs to be used as anion exchangers to
immobilize anionic inhibitors, such as molybdate [31], vanadate [32],
phosphates [33], tungstate anions [34], and other organic anions [35].
These inhibitors can be actively released by an anion exchange process
with chloride ions.
Metal-organic frameworks (MOFs) have been attracting considerable
attention because of the exhibited excellent features, such as a tunable
interior structure, high specific surface area, and easy surface functionalization. As a result, MOFs are promising candidates for applications
in catalysis [36], sensors [37], gas storage [38], and drug delivery systems [39]. Several recent studies have applied MOFs-based nanoparticles for corrosion protection [40-44]. For example, ZIFs with the same
topological structure as zeolites have been synthesized by precipitation from a mixture of a methanol solution containing zinc cations and
2-methylimidazole. Corrosion inhibitors such as benzotriazole (BTA)
can be loaded on the ZIF nanoparticles via ligand exchange [45-47].
Compared to other micro/nanocarriers, ZIF nanoparticles exhibited outstanding thermal stabilities, chemical compatibility and high inhibitor
loading capacity (~65%) [46,48,49].
In the following sections, recent studies on self-healing corrosion protective coatings with the aforementioned types of micro/nanocarriers are discussed.
20
T. Liu, L. Ma, X. Wang et al.
Corrosion Communications 1 (2021) 18–25
fluence the mechanical properties of the coating; in addition, the corrosion inhibitor can achieve a controllable release effect through the carrier. Furthermore, a small amount of appropriate corrosion inhibitors is
usually sufficient to achieve a corrosion inhibition effect. However, the
effect of the corrosion inhibitor does not improve the barrier properties
of the coating itself. Thus, a long-term self-healing effect depends on
the durable and irreversible inhibitive ability [69]. The categories and
reaction mechanisms of inhibitor carriers have been discussed in detail
in several other reviews [3,17,21].
In self-healing corrosion protective coatings, hollow mesoporous silica nanocontainers (HMSNs) are widely selected to convey inhibitors
because of their biocompatibility, high stability, large specific surface area (700–1000 m2 g–1 ), high pore volume (0.6–1 cm2 g–1 ), and
the presence of organic functional groups. HMSNs can be either hydrophilic or hydrophobic depending on the silanol molecules. The presence of organic functional groups can provide a possible functionalization of HMSNs [70]. In early investigations, corrosion inhibitors such
as 8-hydroxyquinoline (8HQ) [71], BTA [72,73], mercaptobenzothiazol
(MBT) [74,75], dodecyl amine [76], cerium nitrate [77], or ammonium
salts [78], were loaded into HMSMs without any modification or functionalization of the container surface. The encapsulation process was
achieved by simply mixing the HMSNs suspension with the inhibitor
solution under reduced pressure [71]. The main disadvantage of this
method was related to the premature leakage of inhibitors caused by the
connectivity within and outside the mesoporous containers. In addition
to HMSNs, other nanocontainers that have been used as inhibitor containers are halloysite nanotubes [79,80], montmorillonite nanoparticles
[81], TiO2 [82], LDHs [83,84], zeolites [85,86], and some bio-based
micro/nanoparticles [87].
Stimuli-sensitive organic molecules can be used to functionalize the
surface of inorganic nanocarriers to achieve intelligent delivery of corrosion inhibitors in response to environmental changes during the corrosion process. The most commonly reported triggering mechanisms
are based on pH variation or redox reaction during corrosion. Corrosion processes involve the dissolution of the anode and the reduction
reaction on the cathode, which inevitably changes the pH of the local corrosion area. Depending on the type of the metallic substrate and
the nature of the corrosion process, the increase or decrease in pH values was used as the basis to unlock the shell of the nanocarriers to release the stored corrosion inhibitors [88]. For example, Li et al. encapsulated poly(methacrylic acid) (PMAA) into silica-based nanotubes by
surface-graft polymerization for pH-responsive release of BTA corrosion
inhibitors [89]. In addition, pH-responsive containers can be produced
by enclosing an inorganic nanoparticle core with a polyelectrolyte multilayer outer shell based on electrostatic layer-by-layer (LbL) assembly
[90]. Corrosion inhibitors can serve as the constituents of LbL multilayers or be encapsulated within LbL micro/nanocontainers [91].
Recently, Shchukin et al. [92] deposited tannic acid (TA) on HMSNs to endow a pH-controlled release behavior of the BTA corrosion
inhibitors. TA is a type of nontoxic and biodegradable polyphenol chemical compound extracted from tree bark, and has often been used as a
corrosion inhibitor [93,94]. The synthesis process of the MSN-BTA@TA
container and its pH-sensitive mechanism are shown in Fig. 4. The controlled release of BTA and TA inhibitors was achieved through the dissociation of TA and Fe3+ complexes on the carrier surface when the pH
decreased due to corrosion activities on the steel substrate. EIS and microscopy measurements confirmed that the water-borne alkyd coating
blended with 2 wt% of nanocontainers showed the optimal self-healing
effect after 20 d of immersion in 0.1 mol L−1 NaCl solution.
The self-healing ability in corrosion protective coatings can also be
obtained by introducing redox-responsive capsules. Compared to pHresponsive microspheres, redox-responsive capsules can be more sensitive and specific to corrosion processes [51,95]. For example, Rohwerder et al. [95] developed a self-healing coating on zinc based
on polyaniline (PANI) nanocapsules containing 3-nitrosalicylic acid
(3-NisA) as a corrosion inhibitor. The cyclic voltammograms (CV) of
Fig. 2. Preparation of capsules with a PU/silica shell and inhibitor HDI core
[59] (Reproduced from Ref. [59] with permission from the Royal Society of
Chemistry).
coatings [61-63]. Recently, Zhou et al. [61] used linseed oil as a healing agent and fabricated microcapsules with excellent properties using
in situ polymerization. The thermogravimetric analysis confirmed that
the linseed oil content was as high as 82 wt%, which could be sufficient
to repair coating damage of particular sizes as shown in Fig. 3. The
linseed oil formed a solid film within the damaged area to provide a
barrier for the coating. In addition, Mirabedini and coworkers [62] prepared microcapsules filled with linseed oil by in situ UF polymerization.
The results reveal that the effect of microcapsule size (~20–100 𝜇m) on
the self-healing performance was more significant than that of microcapsule concentration, that is, larger microcapsules were more likely to
rupture during the damage process and resulted in a superior repairing effect. The results from electrochemical impedance spectroscopy
(EIS) measurement also revealed that the barrier effect of linseed oil
was short-term and would decline rapidly as the immersion time was
extended. Tung oils possess similar performances to linseed oils. Using
liquid Tung oil as the core material, Tian et al. fabricated three calcium
alginate microcapsules with different sizes (1 𝜇m, 500 nm, and 200 nm)
via in situ polymerization [63]. The effects of microcapsule size on the
self-healing, wear resistance, and corrosion resistance of the as-prepared
coating were investigated. The results revealed that the capsule-doped
coating exhibited superior self-healing performance, higher wear resistance, and improved corrosion resistance.
4. Coatings with micro/nanocarriers containing corrosion
inhibitors
Self-healing processes can also be achieved by implanting corrosion
inhibitors into coatings. Several reviews [64-68] have summarized different types of inhibitors. During the corrosion process, the cathodic
reactions and anodic dissolution on the exposed metal surface in the
damaged area of the coating can be generally suppressed by the corrosion inhibitors released from the breakage in the coating. Using steel
substrates as an example, their cathodic corrosion reactions in a neutral environment can be suppressed by cathodic inhibitors (such as salts
containing Zn, Ca, Mg, Ni, Mn, or rare earth element cations), which
induce the precipitation of oxides and hydroxides on the exposed metal
surface. The control of anodic dissolution can be achieved by anodic inhibitors (such as chromate, nitrite, molybdate, and tungstate) that can
passivate the metal surface. In most cases, the inhibitors exhibit a mixed
behavior that reduces the current densities of both cathodic and anodic reactions using chemical reaction or physical adsorption, or both,
on the exposed metal substrates. Inhibitor-containing coatings constitute a large proportion of all reported self-healing corrosion protective
coatings. Compared with self-healing coatings based on polymerizable
agents, inhibitor-containing coatings repair corrosion damages by directly decelerating the corrosion processes. This strategy is also advantageous because the solid phase of the corrosion inhibitors does not in21
T. Liu, L. Ma, X. Wang et al.
Corrosion Communications 1 (2021) 18–25
Fig. 3. Scanning electron microscopy images of the damaged area of the pure epoxy (a) and microcapsules-embedded coatings (b) [61]. (Reproduced from Ref.
[61] with permission from the Elsevier).
Fig. 4. Synthesis of MSN-BTA@TA nanocontainers and their pH-responsive
mechanisms [92]. (Reproduced from Ref. [92] with permission from the Elsevier).
PANI capsules depicted reversible redox responses and changes of the
chemical structure in the shell material in 0.5 mol L−1 KCl solution
(Fig. 5(A)), suggesting the ability of the PANI capsules to sense changes
of electrochemical potential in the surrounding environment. The release of 3-NisA corrosion inhibitor was studied by ultraviolet-visible absorption spectroscopy under three different potential states that could
simulate different corrosion conditions (Fig. 5(B)) including, (a) no potential state to simulate the intact coating, (b) low potential state to
simulate the onset of corrosion and the reduction of PANI, and (c) high
potential state to stimulate the passivation of the metal. As depicted
in Fig. 5(C), the dissolution of the metal releases cations, the incorporation of which causes a change in the volume and permeability of
PANI capsules, thereby enabling the release of the corrosion inhibitors.
In addition, this strategy could provide a self-healing effect, even in
the case of large-scale damage, because as long as corrosion occurs,
the controlled release of inhibitors would be enabled by spreading of
the triggering signal (metal cations). Another strategy based on redoxresponsive nanocontainers was reported by Sun et al. [96]. They developed a redox-responsive mesoporous silica nanocontainer that was covered by ZnO quantum dots. The corrosion inhibitor MBT could be successfully loaded into the mesoporous silica nanocontainers with a low
leakage of 4.9% because ZnO quantum dots were covalently bonded on
the silica shell nanocontainers by the disulfide bond-conjugated amide
bond. The disulfide linkage could be broken by dithiothreitol (DTT) as
a redox stimulus (reducing agent) to release the encapsulated MBT.
Protective organic coatings are often exposed to harsh environments with high chloride levels. Therefore, micro/nanocapsules that
can change their shell structures in response to saline environments
are highly desired [97-99]. For this purpose, Zhang et al. demonstrated
a NaCl-sensitive polyelectrolyte microcapsule with the ability to con-
Fig. 5. (A) CV curves of PANI capsule in 0.5 mol L−1 KCl on the gold electrode.
(B) Cumulative release of 3-NisA inhibitor from PANI capsules under reduced
and oxidized processes. The gray region (b, d) depicted the period during which
the nanocapsules were reduced (−500 mV) and the regions with the white background show the oxidized condition (a) or reoxidized condition of the capsules
(c). (C) Schematic illustration of the release mechanism [95]. (Reproduced from
Ref. [95] with permission from the John Wiley and Sons).
trol to release of hydrophobic active agents (i.e. dodecane, iodobenzene, or the healing agents of E51) [97]. As shown in Fig. 6, the hydrophobic domains allow active agents to be trapped in the capsule
shell and the oil cannot be released due to the oil/water interfacial
tension. With different NaCl concentrations (0.1−0.6 mol L−1 ), the repair agent can be released by a fast or slow process. At high NaCl
concentrations, the rapid release was due to the disassembly of the
polyelectrolyte shell as Na+ and Cl− could break the electrostatic interactions of the polyelectrolyte, as seen in Fig. 6. For the slow release process at low NaCl concentrations (e.g. 0.1 mol L−1 ), the interaction between dimethyl dioctadecyl ammonium bromide (DDAB)
and poly (dimethyl diallyl ammonium chloride)-cellulose nanocrystal/poly sodium-4-styrenesulfonate (P-C/PSS) networks based on monoelectrostatic interaction was broken. The micelles formed by the dissociated DDAB encapsulated the oil and were dispersed into the water. In
addition, Dolatkhah et al. [99] report a NaCl-responsive capsule based
on the PANI shell (Fig. 7). When the capsule was exposed to a NaCl solution, the PANI shell complexed with the sodium ions resulting in chain
entanglement, which increased the permeability of the PANI shell and
released the corrosion inhibitor (i.e. BTA) to suppress corrosion.
22
T. Liu, L. Ma, X. Wang et al.
Corrosion Communications 1 (2021) 18–25
rosion, which was attributed to oxide/hydroxide precipitation at the cathodic sites. In a study by Asadi et al., imidazole dicarboxylic acid (IDC)
and Zn2+ were simultaneously doped into the halloysite nanotubes embedded in an epoxy ester coating. The synergistic inhibition effect originated from the chelation between the IDC molecules and zinc cations
that formed a complex film at the exposed steel surface [101]. Raj et al.
recently developed a self-healing epoxy coating for corrosion protection of carbon steel based on calcium carbonate hollow spheres containing polyethylenimine (PEI) and triethanolamine (TEA) [102]. The
co-doping of the two inhibitors ensured a more complete coverage and
effective adsorption on the steel surface.
Such synergy can be also obtained between a corrosion inhibitor
and another type of healing agent. Cotting et al. [103] encapsulated
the octyl silanol healing agent and Ce(III)-based corrosion inhibitor in
polystyrene (PS) microcapsules and prepared a self-healing epoxy coating on mild carbon steel. The Ce(III) inhibitor can suppress the reduction reaction in the cathode area, whereas the release of octyl silanol
can form a barrier film on the damaged area by self-oxidative polymerization. Leal et al. prepared double stimuli-responsive microcarriers containing linseed oil as the core material and used the LbL polyelectrolyte shell to trap the BTA corrosion inhibitor [104]. The resultant microcarriers had a multilayer structure: oil-core microcapsules,
oil core/PEI/poly(styrene sulfonate) (PSS)/BTA/PSS/PEI. The release of
linseed oil by mechanical stimulus and the controlled release of BTA by
the pH stimulus of the corrosion reaction synergistically promoted the
self-healing functions. In a recent study by our group, the 8HQ corrosion inhibitor was entrapped in polycaprolactone (PCL) microcontainers
that were incorporated into the shape memory epoxy coating on the aluminum alloy [105]. The microcontainers can release 8HQ using a pHsensitive technique attributed to the hydrolytic degradation of PCL. As
a thermoplastic material, the PCL microcontainers can melt under mild
heat and fill the coating defect, thus forming an inhibitor-enhanced barrier on the exposed metal substrate.
Fig. 6. Schematic of the slow and fast release process of oil in a corrosive environment [97]. (Reproduced from Ref. [97] with permission from the American
Chemical Society).
6. Conclusions and outlook
This paper provides a brief and updated overview of
micro/nanocarrier-based self-healing corrosion protective coatings
by considering mainstream encapsulation techniques and self-healing
coatings with micro/nanocarriers that contained polymerizable agents,
corrosion inhibitors or a mixture of multiple healing agents. Although
the promising performance was demonstrated in existing examples, several outstanding issues have yet to be sufficiently addressed; however,
they are deemed important for the future development of corrosion
protective coatings with enhanced and durable self-healing actions.
For instance, it is necessary to continue the search for environmentally friendly, economic, and sustainable corrosion inhibitors and polymerizable agents for the industrial-scale application of self-healing coatings. Corrosion inhibitors must be appropriately selected based on the
comprehensive understanding of the localized corrosion environment
in the coating damage region as well as the specific interaction between an inhibitor and a specific metal substrate. To this end, the micro/nanoscale mapping of chemical and electrochemical information in
the coating damage region could be extremely useful.
The optimization of the dispersion and location of micro/nanocarriers in the coating matrix is a major challenge requiring a
careful balance of the surface chemistry, compatibility, and density of
the carriers. The carriers utilized in most self-healing coatings release
healing agents either passively or in response to a single stimulus.
Consequently, the design of carriers that are responsive to multiple
stimuli will be beneficial for achieving more efficient and intelligent
releases.
The healing effects in extrinsic self-healing coatings primarily depend on the properties of the carriers and the healing agents but can
be significantly enhanced by the selection of a suitable coating resin.
For example, shape memory polymer coatings capable of reducing the
Fig. 7. Capsules were prepared by employing emulsion polymerization (a) and
illustration of NaCl-responsive controlled-release mechanism (b) [99]. (Reproduced from Ref. [99] with permission from the American Chemical Society).
5. Coatings with micro/nanocarriers containing multiple healing
agents
As discussed in previous sections, neither corrosion inhibitors nor
polymerizable agents can completely heal the coating damage or restore
the barrier effect of the coating. Based on this limitation, an increasing
number of studies began to incorporate multiple healing agents in the
same or different carriers into a coating to synergize and strengthen the
self-healing effect. For instance, the synergistic combinations of inhibiting species, which include Ce3+ , 8-HQ, salicylaldoxime (SAL), and 2,5dimercapto-1,3,4-thiadiazolate (DMTD), were studied by loading single
inhibitor or binary mixtures into calcium carbonate microparticles and
then added to the water-based epoxy coating on the AA2024-T3 alloy
[100]. The results indicated that after two weeks of immersion the highest synergy was observed for the combination of Ce3+ and SAL. In the
early stage of corrosion, SAL could effectively inhibit metal corrosion
via the generation of insoluble chelates with aluminum ions. However,
the release of Ce3+ was advantageous for the long-term inhibition of cor23
T. Liu, L. Ma, X. Wang et al.
Corrosion Communications 1 (2021) 18–25
damage size are expected to decrease the amount of healing agent required to achieve sufficient repair. Conductive polymer coatings may
be used in combination with redox-responsive carriers to achieve the
long-range transmission of redox signals beneath the coating defect/
delamination.
At present, most studies only offer the short-term assessment of selfhealing efficiency using immersion and salt spray tests. Hence, the evaluation of these coatings using long-term degradation tests, particularly
in actual service environments, would be critical for understanding the
healing process and the deterioration of the healing effect.
[22] E. Shchukina, H. Wang, D.G. Shchukin, Nanocontainer-based self-healing coatings: current progress and future perspectives, Chem. Commun. 55 (2019) 3859–
3867.
[23] E.N. Brownt, M.R. Kessler, N.R. Sottos, S.R. White, In situ poly(urea-formaldehyde)
microencapsulation of dicyclopentadiene, J. Microencapsul. 20 (2003) 719–730.
[24] S.K. Ghosh, Self-healing Materials: Fundamentals, Design Strategies, and Applications, Wiley Online Library, America, 2009.
[25] J. Yang, M.W. Keller, J.S. Moore, S.R. White, N.R. Sottos, Microencapsulation of
isocyanates for self-healing polymers, Macromolecules 41 (2008) 9650–9655.
[26] S.U. Pickering, CXCVI.—emulsions, J. Chem. Soc. Trans. 91 (1907) 2001–2021.
[27] O. Velev, K. Furusawa, K. Nagayama, Assembly of latex particles by using emulsion
droplets as templates. 2. Ball-like and composite aggregates, Langmuir 12 (1996)
2385–2391.
[28] W. StöBer, A. Fink, E. Bohn, Controlled growth of monodisperse silica spheres in
the micron size range, J. Colloid Interface Sci. 26 (1968) 62–69.
[29] Q. Wang, D. O’Hare, Recent advances in the synthesis and application of layered
double hydroxide (LDH) nanosheets, Chem. Rev. 112 (2012) 4124–4155.
[30] L. Guo, W. Wu, Y. Zhou, F. Zhang, R. Zeng, Layered double hydroxide coatings on
magnesium alloys: a review, J. Mater. Sci. Technol. 34 (2018) 1455–1466.
[31] R. Zeng, Z. Liu, F. Zhang, S. Li, H. Cui, E. Han, Corrosion of molybdate intercalated
hydrotalcite coating on AZ31 Mg alloy, J. Mater. Chem. A 2 (2014) 13049–13057.
[32] J. Tedim, M. Zheludkevich, A. Bastos, A. Salak, A. Lisenkov, M. Ferreira, Influence
of preparation conditions of layered double hydroxide conversion films on corrosion protection, Electrochim. Acta 117 (2014) 164–171.
[33] E. Alibakhshi, E. Ghasemi, M. Mahdavian, B. Ramezanzadeh, S. Farashi, Active
corrosion protection of Mg-Al-PO43-LDH nanoparticle in silane primer coated with
epoxy on mild steel, J. Taiwan Inst. Chem. Eng. 75 (2017) 248–262.
[34] D. Li, F. Wang, Y. Xiang, J. Wang, L. Qi, P. Yang, H. Yang, Y. Wang, M. Zhang,
Anticorrosion organic coating with layered double hydroxide loaded with corrosion
inhibitor of tungstate, Prog. Org. Coat. 71 (2011) 302–309.
[35] M. Serdechnova, A.N. Salak, F.S. Barbosa, D.E.L. Vieira, M.G.S. Ferreira, Interlayer
intercalation and arrangement of 2-mercaptobenzothiazolate and 1,2,3-benzotriazolate anions in layered double hydroxides: In situ X-ray diffraction study, J. Solid
State Chem. 233 (2016) 158–165.
[36] C. Wang, J. Tuninetti, Z. Wang, C. Zhang, R. Ciganda, L. Salmon, S. Moya, J. Ruiz,
D. Astruc, Hydrolysis of ammonia-borane over Ni/ZIF-8 nanocatalyst: High efficiency, mechanism, and controlled hydrogen release, J. Am. Chem. Soc. 139 (2017)
11610–11615.
[37] L. He, Y. Liu, J. Liu, Y. Xiong, J. Zheng, Y. Liu, Z. Tang, Core-shell noble-metal@metal-organic-framework nanoparticles with highly selective sensing
property, Angew. Chem. Int. Ed. 125 (2013) 3829–3833.
[38] R. Banerjee, A. Phan, B. Wang, C. Knobler, H. Furukawa, M. O’Keeffe, O.M. Yaghi,
High-throughput synthesis of zeolitic imidazolate frameworks and application to
CO2 capture, Science 319 (2008) 939–943.
[39] Y. Li, J. Tang, L. He, Y. Liu, Y. Liu, C. Chen, Z. Tang, Core-shell upconversion
nanoparticle@metal-organic framework nanoprobes for luminescent/magnetic dual-mode targeted imaging, Adv. Mater. 27 (2015) 4075–4080.
[40] C. Wu, Q. Liu, R. Chen, J. Liu, J. Wang, Fabrication of ZIF-8@SiO2 micro/nano
hierarchical superhydrophobic surface on AZ31 magnesium alloy with impressive
corrosion resistance and abrasion resistance, ACS Appl. Mater. Interfaces 9 (2017)
11106–11115.
[41] W. Na, Y. Zhang, J. Chen, Z. Jing, Q. Fang, Dopamine modified metal-organic
frameworks on anti-corrosion properties of waterborne epoxy coatings, Prog. Org.
Coat. 109 (2017) 126–134.
[42] W. Li, B. Ren, Y. Chen, X. Wang, R. Cao, Excellent efficacy of MOF films for
bronze artwork conservation: the key role of HKUST-1 film nanocontainers in selectively positioning and protecting inhibitors, ACS Appl. Mater. Interfaces 10 (2018)
37529–37534.
[43] A. Phan, C.J. Doonan, F.J. Uribe-Romo, C.B. Knobler, M. O’Keeffe, O.M. Yaghi,
Synthesis, ftructure, and carbon dioxide capture properties of zeolitic imidazolate
frameworks, Acc. Chem. Res. 43 (2010) 58–67.
[44] Y. Pan, Y. Liu, G. Zeng, L. Zhao, Z. Lai, Rapid synthesis of zeolitic imidazolate framework-8 (ZIF-8) nanocrystals in an aqueous system, Chem. Commun. 47 (2011)
2071–2073.
[45] Y. Zhao, F. Jiang, Y.Q. Chen, J.M. Hu, Coatings embedded with GO/MOFs nanocontainers having both active and passive protecting properties, Corros. Sci. 168
(2020) 108563.
[46] S. Yang, J. Wang, W. Mao, D. Zhang, Y. Guo, Y. Song, J.P. Wang, T. Qi, G.L. Li,
pH-responsive zeolitic imidazole framework nanoparticles with high active inhibitor content for self-healing anticorrosion coatings, Colloid. Surf. A-Physicochem. Eng. Asp. 555 (2018) 18–26.
[47] Y. Guo, J. Wang, D. Zhang, T. Qi, G.L. Li, pH-responsive self-healing anticorrosion
coatings based on benzotriazole-containing zeolitic imidazole framework, Colloid.
Surf. A-Physicochem. Eng. Asp. 561 (2019) 1–8.
[48] W. Zhang, X. Jiang, X. Wang, Y.V. Kaneti, Y. Chen, J. Liu, J.S. Jiang, Y. Yamauchi,
M. Hu, Spontaneous weaving of graphitic carbon networks synthesized by pyrolysis
of ZIF-67 crystals, Angew. Chem. Int. Ed. 56 (2017) 8435–8440.
[49] M. Zhang, L. Ma, L. Wan, Y.Sun Sun, Y. Liu, Insights into the use of metal-organic
framework as high-performance anticorrosion coatings, ACS Appl. Mater. Interfaces 10 (2018) 2259–2263.
[50] S.R. White, N.R. Sottos, P.H. Geubelle, J.S. Moore, S. Viswanathan, Autonomic
healing of polymer composites, Nature 409 (2001) 794–797.
[51] L.P. Lv, Y. Zhao, N. Vilbrandt, M. Gallei, A. Vimalanandan, M. Rohwerder, K. Landfester, D. Crespy, Redox responsive release of hydrophobic self-healing agents from
polyaniline capsules, J. Am. Chem. Soc. 135 (2013) 14198–14205.
Conflicts of interest
All of authors declare no competing financial interest.
Acknowledgements
This work was financially supported by the National Natural Science Foundation of China (Nos. 51771029 and 51901015) and the China
Postdoctoral Science Foundation (No. 2018M641189).
References
[1] X. Li, D. Zhang, Z. Liu, Z. Li, C. Du, C. Dong, Materials science: share corrosion
data, Nature 527 (2015) 441–442.
[2] B. Hou, X. Li, X. Ma, C. Du, D. Zhang, M. Zheng, W. Xu, D. Lu, F. Ma, The cost of
corrosion in China, Npj Mater. Degrad. 1 (2017) 1–10.
[3] F. Zhang, J.P. Ju, M. Pan, D. Zhang, Y. Huang, G. Li, X. Li, Self-healing mechanisms
in smart protective coatings: a review, Corros. Sci. 144 (2018) 74–88.
[4] K. Jud, H.H. Kausch, J.G. Williams, Fracture mechanics studies of crack healing
and welding of polymers, J. Mater. Sci. 16 (1981) 204–210.
[5] D.V. Andreeva, D.G. Shchukin, Smart self-repairing protective coatings, Mater. Today 11 (2008) 24–30.
[6] H. Qian, D. Xu, C. Du, D. Zhang, X. Li, L. Huang, L. Deng, Y. Tu, J.M. Mol, H.A. Terryn, Dual-action smart coatings with a self-healing superhydrophobic surface and
anti-corrosion properties, J. Mater. Chem. A 5 (2017) 2355–2364.
[7] L. Wang, L. Deng, D. Zhang, H. Qian, C. Du, X. Li, J.M.C. Mol, H.A. Terryn, Shape
memory composite (SMC) self-healing coatings for corrosion protection, Prog. Org.
Coat. 97 (2016) 261–268.
[8] D. Zhang, L. Wang, H. Qian, X. Li, Superhydrophobic surfaces for corrosion protection: A review of recent progresses and future directions, J. Coat. Technol. Res. 13
(2016) 11–29.
[9] S. Schäfer, G. Kickelbick, Double reversible networks: improvement of self-healing in hybrid materials via combination of diels–Alder cross-linking and hydrogen
bonds, Macromolecules 51 (2018) 6099–6110.
[10] A. Gandini, A.J. Silvestre, D. Coelho, Reversible click chemistry at the service of
macromolecular materials. 2. Thermoreversible polymers based on the Diels-Alder
reaction of an A-B furan/maleimide monomer, J. Polym. Sci. Part A: Polym. Chem.
48 (2010) 2053–2056.
[11] J. Canadell, H. Goossens, B. Klumperman, Self-healing materials based on disulfide
links, Macromolecules 44 (2011) 2536–2541.
[12] Y. Amamoto, J. Kamada, H. Otsuka, A. Takahara, K. Matyjaszewski, Repeatable
photoinduced self-healing of covalently cross-linked polymers through reshuffling
of trithiocarbonate units, Angew. Chem. Int. Ed. 50 (2011) 1660–1663.
[13] Y. Song, Y. Liu, T. Qi, G.L. Li, Towards dynamic but supertough healable polymers
through biomimetic hierarchical hydrogen-bonding interactions, Angew. Chem.
Int. Ed. 57 (2018) 13838–13842.
[14] B.A. Blight, C.A. Hunter, D.A. Leigh, H. McNab, P.I. Thomson, An AAAA–DDDD
quadruple hydrogen-bond array, Nature Chem 3 (2011) 244–248.
[15] H. Ying, Y. Zhang, J. Cheng, Dynamic urea bond for the design of reversible and
self-healing polymers, Nat. Commun. 5 (2014) 1–9.
[16] A.S.H. Makhlouf, N. Abu-Thabit, Advances in Smart Coatings and Thin Films for
Future Industrial and Biomedical Engineering Applications, Elsevier, Netherlands,
2019.
[17] D. Zhu, M. Rong, M. Zhang, Self-healing polymeric materials based on microencapsulated healing agents: From design to preparation, Prog. Polym. Sci. 49 (2015)
175–220.
[18] H. Wei, Y. Wang, J. Guo, N.Z. Shen, D. Jiang, X. Zhang, X. Yan, J. Zhu, Q. Wang,
L. Shao, Advanced micro/nanocapsules for self-healing smart anticorrosion coatings, J. Mater. Chem. A 3 (2015) 469–480.
[19] H. Ullah, K.A.M Azizli, Z.B. Man, M.B.C. Ismail, M.I. Khan, The potential of microencapsulated self-healing materials for microcracks recovery in self-healing
composite systems: a review, Polym. Rev. (2016) 1–57.
[20] S. An, M.W. Lee, A.L. Yarin, S.S. Yoon, A review on corrosion-protective extrinsic self-healing: Comparison of microcapsule-based systems and those based on
core-shell vascular networks, Chem. Eng. J. 344 (2018) 206–220.
[21] K. Ye, Z. Bi, G. Cui, B. Zhang, Z. Li, External self-Healing coatings in anticorrosion
applications: a review, Corrosion 76 (2020) 279–298.
24
T. Liu, L. Ma, X. Wang et al.
Corrosion Communications 1 (2021) 18–25
[52] H. Yi, Y. Deng, C. Wang, Pickering emulsion-based fabrication of epoxy and amine
microcapsules for dual core self-healing coating, Compos. Sci. Technol. 133 (2016)
51–59.
[53] M.A.S. Al-Maadeed, TiO2 nanotubes and mesoporous silica as containers in self-healing epoxy coatings, Sci. Rep. 6 (2016) 38812.
[54] X. Cai, D. Fu, A. Qu, Optimization of preparation conditions of epoxy-containing
nanocapsules, Sci. Eng. Compos. Mater. 24 (2017) 155–161.
[55] W. Meesorn, C. Calvino, J.C. Natterodt, J.O. Zoppe, C. Weder, Bio-inspired, self–
toughening polymers enabled by plasticizer-releasing microcapsules, Adv. Mater.
31 (2019) 1807212.
[56] W. Wang, L. Xu, F. Liu, X. Li, L. Xing, Synthesis of isocyanate microcapsules and
micromechanical behavior improvement of microcapsule shells by oxygen plasma
treated carbon nanotubes, J. Mater. Chem. A 1 (2012) 776–782.
[57] N.W. Khun, H. Zhang, D.W. Sun, J.L. Yang, Tribological behaviors of binary and
ternary epoxy composites functionalized with different microcapsules and reinforced by short carbon fibers, Wear 350 (2016) 89–98.
[58] D. Sun, H. Zhang, X.Z. Tang, J. Yang, Water resistant reactive microcapsules for
self-healing coatings in harsh environments, Polymer 91 (2016) 33–40.
[59] G. Wu, J. An, D. Sun, X. Tang, Y. Xiang, J. Yang, Robust microcapsules with
polyurea/silica hybrid shell for one-part self-healing anticorrosion coatings, J.
Mater. Chem. A 2 (2014) 11614–11620.
[60] M. Huang, J. Yang, Facile microencapsulation of HDI for self-healing anticorrosion
coatings, J. Mater. Chem. 21 (2011) 11123–11130.
[61] S. Lang, Q. Zhou, Synthesis and characterization of poly(urea-formaldehyde) microcapsules containing linseed oil for self-healing coating development, Prog. Org.
Coat. 105 (2017) 99–110.
[62] M. Behzadnasab, S.M. Mirabedini, M. Esfandeh, R.R. Farnood, Evaluation of corrosion performance of a self-healing epoxy-based coating containing linseed oil-filled
microcapsules via electrochemical impedance spectroscopy, Prog. Org. Coat. 105
(2017) 212–224.
[63] J. Sun, Y. Wang, N. Li, L. Tian, Tribological and anticorrosion behavior of self-healing coating containing nanocapsules, Tribol. Int. 136 (2019) 332–341.
[64] P.B. Raja, M.G. Sethuraman, Natural products as corrosion inhibitor for metals in
corrosive media—a review, Mater. Lett. 62 (2008) 113–116.
[65] D.E. Arthur, A. Jonathan, P.O. Ameh, C. Anya, A review on the assessment of polymeric materials used as corrosion inhibitor of metals and alloys, Int. J. Ind. Chem.
4 (2013) 2.
[66] M. Goyal, S. Kumar, I. Bahadur, C. Verma, E.E. Ebenso, Organic corrosion inhibitors
for industrial cleaning of ferrous and non-ferrous metals in acidic solutions: A review, J. Mol. Liq. 256 (2018) 565–573.
[67] C. Verma, E.E. Ebenso, M. Quraishi, Corrosion inhibitors for ferrous and non-ferrous metals and alloys in ionic sodium chloride solutions: a review, J. Mol. Liq.
248 (2017) 927–942.
[68] P. Jain, B. Patidar, J. Bhawsar, Potential of nanoparticles as a corrosion inhibitor:
a review, J. Bio-and Tribo-Corros. 6 (2020) 1–12.
[69] P. Visser, H. Terryn, J.M.C. Mol, On the importance of irreversibility of corrosion inhibitors for active coating protection of AA2024-T3, Corros. Sci. 140 (2018)
272–285.
[70] A. Maleki, H. Kettiger, A. Schoubben, J.M. Rosenholm, M. Hamidi, Mesoporous silica materials: From physico-chemical properties to enhanced dissolution of poorly
water-soluble drugs, J. Control. Release 262 (2017) 329–347.
[71] E. Shchukina, D. Shchukin, D. Grigoriev, Effect of inhibitor-loaded halloysites
and mesoporous silica nanocontainers on corrosion protection of powder coatings,
Prog. Org. Coat. 102 (2017) 60–65.
[72] D. Borisova, H. MöHwald, D.G. Shchukin, Mesoporous silica nanoparticles for active corrosion protection, ACS Nano 5 (2011) 1939–1946.
[73] I. Recloux, M. Mouanga, M.E. Druart, Y. Paint, M.G. Olivier, Silica mesoporous thin
films as containers for benzotriazole for corrosion protection of 2024 aluminium
alloys, Appl. Surf. Sci. 346 (2015) 124–133.
[74] D. Borisova, D. Akçakayıran, M. Schenderlein, H. Möhwald, D.G. Shchukin,
Nanocontainer-based anticorrosive coatings: effect of the container size on the self-healing performance, Adv. Funct. Mater. 23 (2013) 3799–3812.
[75] A. Chenan, S. Ramya, R.P. George, U.K. Mudali, 2-Mercaptobenzothiazole-loaded
hollow mesoporous silica-based hybrid coatings for corrosion protection of modified 9Cr-1Mo ferritic steel, Corrosion 70 (2014) 496–511.
[76] J.M. Falcón, L.M. Otubo, I.V. Aoki, Highly ordered mesoporous silica loaded with
dodecylamine for smart anticorrosion coatings, Surf. Coat. Technol. 303 (2015)
319–329.
[77] R. Noiville, O. Jaubert, M. Gressier, J.P. Bonino, P.L. Taberna, B. Fori, M.-J. Menu,
Ce(Ⅲ) corrosion inhibitor release from silica and boehmite nanocontainers, Mater.
Sci. Eng. B 229 (2018) 144–154.
[78] W.C. Changjean, L.Y. Huang, P.Y. Liu, T.C. Tsai, Repairable mesoporous silica film
with replenishing corrosion inhibitor as corrosion protection layer of aluminum
alloy, Microporous Mesoporous Mat 192 (2014) 82–88.
[79] A. Molaei, A. Amadeh, M. Yari, M.R. Afshar, Structure, apatite inducing ability,
and corrosion behavior of chitosan/halloysite nanotube coatings prepared by electrophoretic deposition on titanium substrate, Mater. Sci. Eng. C 59 (2016) 740–747.
[80] M. Sun, A. Yerokhin, M.Y. Bychkova, D.V. Shtansky, E.A. Levashov, A. Matthews,
Self-healing plasma electrolytic oxidation coatings doped with benzotriazole
[81]
[82]
[83]
[84]
[85]
[86]
[87]
[88]
[89]
[90]
[91]
[92]
[93]
[94]
[95]
[96]
[97]
[98]
[99]
[100]
[101]
[102]
[103]
[104]
[105]
25
loaded halloysite nanotubes on AM50 magnesium alloy, Corros. Sci. 111 (2016)
753–769.
A. Ghazi, E. Ghasemi, M. Mandavian, B. Ramezanzadeh, M. Rostami, The application of benzimidazole and zinc cations intercalated sodium montmorillonite as
smart ion exchange inhibiting pigments in the epoxy ester coating, Corros. Sci. 94
(2015) 207–217.
X. Liu, C. Gu, Z. Ma, X. Ma, B. Hou, pH-responsive containers based on modified
hollow TiO2 for active and passive protection of carbon steel, J. Electrochem. Soc.
165 (2018) 145–154.
M. Mohedano, M. Serdechnova, M. Starykevich, S. Karpushenkov, A.C. Bouali,
M.G.S. Ferreira, M.L. Zheludkevich, Active protective PEO coatings on AA2024:
role of voltage on in-situ LDH growth, Mater. Des. 120 (2017) 36–46.
M.F. Montemor, D.V. Snihirova, M.G. Taryba, S.V. Lamaka, I.A. Kartsonakis,
A.C. Balaskas, G.C. Kordas, J. Tedim, A. Kuznetsova, M.L. Zheludkevich, Evaluation of self-healing ability in protective coatings modified with combinations of
layered double hydroxides and cerium molibdate nanocontainers filled with corrosion inhibitors, Electrochim. Acta 60 (2012) 31–40.
E.L. Ferrer, A.P. Rollon, H.D. Mendoza, U. Lafont, S.J. Garcia, Double-doped zeolites for corrosion protection of aluminium alloys, Micropor. Mesopor. Mat. 188
(2014) 8–15.
S.P. Zhu, L. Luo, L. Zhang, S.X. Shen, X.X. Ren, M.W. Guo, J.M. Yang, X.Y. Shen,
Y.S. Xu, B. Ji, Acupuncture de-qi: From characterization to underlying mechanism,
Evid.-based Complement Altern. Med. 2013 (2013) 518784.
P.J. Denissen, S.J. Garcia, Cerium-loaded algae exoskeletons for active corrosion
protection of coated AA2024-T3, Corros. Sci. 128 (2017) 164–175.
D.G. Shchukin, H. Möhwald, Self-repairing coatings containing active nanoreservoirs, Small 3 (2007) 926–943.
L.L. Guo, Z. Zheng, H. Möhwald, D.G. Shchukin, Silica/polymer double-walled hybrid nanotubes: synthesis and application as stimuli-responsive nanocontainers in
self-healing coatings, ACS Nano 7 (2013) 2470–2478.
E.V. Skorb, D.V. Andreeva, Self-healing properties of layer-by-layer assembled multilayers, Polym. Int. 64 (2015) 713–723.
G. Decher, Fuzzy nanoassemblies: toward layered polymeric multicomposites, Science 277 (1997) 1232–1237.
B. Qian, M. Michaiidis, M. Bilton, T. Hobson, D. Shchukin, Tannic complexes coated
nanocontainers for controlled release of corrosion inhibitors in self-healing coatings, Electrochim. Acta 297 (2018) 1035–2041.
S. Feliu, J. Galván, S. Feliu Jr, J. Bastidas, J. Simancas, M. Morcillo, E. Almeida, An
electrochemical impedance study of the behaviour of some pretreatments applied
to rusted steel surfaces, Corros. Sci. 35 (1993) 1351–1358.
S. Nasrazadani, The application of infrared spectroscopy to a study of phosphoric and tannic acids interactions with magnetite (Fe3O4), goethite (𝛼-FeOOH) and
lepidocrocite (𝛾-FeOOH), Corros. Sci. 39 (1997) 1845–1859.
A. Vimalanandan, L.P. Lv, T.H. Tran, K. Landfester, D. Crespy, M. Rohwerder,
Redox-responsive self-healing for corrosion protection, Adv. Mater. 25 (2013)
6980–6984.
S. Sun, X. Zhao, M. Cheng, Y. Wang, C. Li, S. Hu, Facile preparation of redox-responsive hollow mesoporous silica spheres for the encapsulation and controlled
release of corrosion inhibitors, Prog. Org. Coat. 136 (2019) 105302.
Y. Zhang, G. Zhu, B. Dong, J. Tang, F. Wang, S. Hong, F. Xing, Salt-triggered release of hydrophobic agents from polyelectrolyte capsules generated via one-step
interfacial multilevel and multicomponent assembly, ACS Appl. Mater. Interfaces
11 (2019) 38353–38360.
J. Wu, D. Zhang, Y. Wang, S. Mao, J. Yang, Electric assisted salt-responsive bacterial
killing and release of polyzwitterionic brushes in low-concentration salt solution,
Langmuir 35 (2019) 8285–8293.
A. Dolatkhah, L.D. Wilson, Saline-responsive and hydrogen bond gating effects in
self-healing polyaniline, ACS Appl. Polym. Mater. 2 (2020) 2311–2318.
D. Snihirova, S. Lamaka, P. Taheri, J. Mol, M. Montemor, Comparison of the
synergistic effects of inhibitor mixtures tailored for enhanced corrosion protection of bare and coated AA2024-T3, Surf. Coat. Technol. 303 (2016) 342–
351.
N. Asadi, R. Naderi, M. Mahdavian, Synergistic effect of imidazole dicarboxylic
acid and Zn2+ simultaneously doped in halloysite nanotubes to improve protection
of epoxy ester coating, Prog. Org. Coat. 132 (2019) 29–40.
R. Raj, Y. Morozov, L. Calado, M. Taryba, R. Kahraman, R. Shakoor, M. Montemor, Calcium carbonate particles loaded with triethanolamine and polyethylenimine for enhanced corrosion protection of epoxy coated steel, Corros. Sci. 167
(2020) 108548.
F. Cotting, I.V. Aoki, Smart protection provided by epoxy clear coating doped
with polystyrene microcapsules containing silanol and Ce (III) ions as corrosion
inhibitors, Surf. Coat. Technol. 303 (2016) 310–318.
D.A. Leal, I.C. Riegel-Vidotti, M.G.S. Ferreira, C.E.Bruno Marino, Smart coating
based on double stimuli-responsive microcapsules containing linseed oil and benzotriazole for active corrosion protection, Corros. Sci. 130 (2018) 56–63.
Y. Huang, L. Deng, P. Ju, L. Huang, H. Qian, D. Zhang, X. Li, H.A. Terryn, J.M. Mol,
Triple-action self-healing protective coatings based on shape memory polymers
containing dual-function microspheres, ACS Appl. Mater. Interfaces 10 (2018)
23369–23379.