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Slippery Surface with Petal-like Structure for Protecting Al Alloy: Anti-corrosion, Anti-fouling and Anti-icing

  • Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences

Abstract and Figures

The harsh working environment affects the performance and usage life of Al and its alloys, thus limiting their application. In recent years, Slippery Liquid-infused Porous Surface (SLIPS) has attracted much attention due to excellent anti-corrosion, anti-fouling and anti-icing properties. This may be an effective way to improve the properties of Al and its alloys. Here, the SLIPS with petal-like structure was constructed on the Al alloy via simple hydrothermal reaction, Stearic Acid (STA) modification and lubricant injection. A variety of droplets (including oil-in-water emulsions) can slide on the SLIPS at a low angle, even the Sliding Angle (SA) of the water droplet is only 3°. Furthermore, the SLIPS exhibits outstanding mechanical and chemical properties. It can maintain fine oil-locking ability under high shearing force and keep slippery stability after immersion in acid/alkaline solutions. In addition, the SLIPS possesses excellent anti-corrosion, anti-fouling and anti-icing properties, which provides a new way to promote the application of Al and its alloys. Therefore, the SLIPS is expected to be an effective way to improve the properties of Al and its alloys, as well as play a role in anti-fouling and self-cleaning in construction, shipbuilding and automotive manufacturing industries, thereby expanding the practical application of Al and its alloys.
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Journal of Bionic Engineering
Slippery Surface withPetal‑like Structure forProtecting Al Alloy:
Anti‑corrosion, Anti‑fouling andAnti‑icing
JunfeiHuang1,3· JiajieKang1,4· JiaxuZhang1,3· JinxiaHuang3· ZhiguangGuo2,3
Received: 21 May 2021 / Revised: 29 October 2021 / Accepted: 14 November 2021
© The Author(s) 2021
The harsh working environment affects the performance and usage life of Al and its alloys, thus limiting their application. In
recent years, Slippery Liquid-infused Porous Surface (SLIPS) has attracted much attention due to excellent anti-corrosion,
anti-fouling and anti-icing properties. This may be an effective way to improve the properties of Al and its alloys. Here,
the SLIPS with petal-like structure was constructed on the Al alloy via simple hydrothermal reaction, Stearic Acid (STA)
modification and lubricant injection. A variety of droplets (including oil-in-water emulsions) can slide on the SLIPS at a low
angle, even the Sliding Angle (SA) of the water droplet is only 3°. Furthermore, the SLIPS exhibits outstanding mechanical
and chemical properties. It can maintain fine oil-locking ability under high shearing force and keep slippery stability after
immersion in acid/alkaline solutions. In addition, the SLIPS possesses excellent anti-corrosion, anti-fouling and anti-icing
properties, which provides a new way to promote the application of Al and its alloys. Therefore, the SLIPS is expected to
be an effective way to improve the properties of Al and its alloys, as well as play a role in anti-fouling and self-cleaning in
construction, shipbuilding and automotive manufacturing industries, thereby expanding the practical application of Al and
its alloys.
Keywords Slippery surface· Al alloy· Anti-corrosion· Anti-fouling· Anti-icing
1 Introduction
As one of the commonly used engineering materials, Al
and its alloys have excellent physical and mechanical prop-
erties, making Al and its alloys widely used, especially in
aerospace, automotive, machinery manufacturing, ship-
building and chemical industry. Therefore, it is inevitable
for them to work in harsh environment, which will cause
great damage to them and affect their usage life. To improve
the usage life of Al and its alloys and expand its application
range, it should be put on agenda that improving the proper-
ties of Al and its alloys under extreme environments [15].
In recent years, it has been considered as a new and effec-
tive way to construct Superhydrophobic Surfaces (SHSs)
on Al and its alloys for prevent corrosion [6, 7]. In addition,
SHSs has attracted much attention in the fields of oil–water
separation [8, 9], anti-icing [1012], self-cleaning [13, 14]
and drag reduction [15] due to its excellent hydrophobic
performance (contact angle greater than 150°). However,
reports have shown that the instability of the hydrophobic
layer and the finiteness of the micro-nano structure led to
the insufficient robustness of SHSs, which makes them easy
to be destroyed under dynamic action and mechanical dam-
age [16, 17]. Hence, the effect of building superhydrophobic
surface on Al and its alloys to improve their performance is
very limited.
* Jiajie Kang
* Jinxia Huang
* Zhiguang Guo
1 School ofEngineering andTechnology, China University
ofGeosciences, Beijing100083, China
2 Ministry ofEducation Key Laboratory fortheGreen
Preparation andApplication ofFunctional Materials, Hubei
University, Wuhan430062, China
3 State Key Laboratory ofSolid Lubrication, Lanzhou Institute
ofChemical Physics, Chinese Academy ofSciences,
Lanzhou730000, China
4 Zhengzhou Institute, China University ofGeosciences
(Beijing), Zhengzhou451283, China
J.Huang et al.
1 3
It is well known that Nepenthes pitcher plants can
capture insects through the slippery surface. The reason
for the formation of slippery surface is that the surface
has a hydrophilic component and the rough structure, so
the surface can store water and form a lubricating water
layer [18]. Inspired by this, Aizenberg etal. proposed
the concept of Slippery Liquid-infused Porous Surface
(SLIPS). They injected lubricating oil into the rough
porous surface to form SLIPS, which showed excellent
characteristics including but not limited to low sliding
angle, extreme pressure stability and optical transparency
[19]. Surprisingly, there are some references pointing out
that SLIPS has excellent repeatable self-healing ability
[1921]. Hence, SLIPS shows better mechanical durability
and robustness than SHS, and SLIPS is expected to be an
effective way to solve SHS failure. Up to now, SLIPS has
become a hot research field, which has attracted the atten-
tion of many scientists. Based on the three principles fol-
lowed in constructing SLIPS: (1) the lubricating liquid and
the repellent liquid are not mutually soluble, (2) compared
with the repellent fluid, the lubricating fluid must have
higher chemical affinity with the substrate, and (3) the
solid surface must be a nano-composite rough structure to
provide large enough surface to absorb and store lubricat-
ing oil [19], many SLIPSs have been made by researchers
and used in various fields. Sun et al. fabricated a stable
superoleophobic–superhydrophilic surface by spraying,
which can separate organic liquid mixtures [22]. Feng et
al. developed a SLIPS with hierarchical Micro-Nanostruc-
tures (MNS-SLIPS) on the basis of regular microporous
structures for long-term efficient water harvesting [23].
Li et al. fabricated a slippery copper oxide surface by a
simple liquid–solid reaction, STA modification and oil-
infused, the surface inhibits corrosion efficiency reached
up to 92.68% [24]. Therefore, building SLIPS on Al and
its alloys may be a promising potential method to improve
its performance and expand its application.
In this work, we have prepared the SLIPS with petal-
like structure on Al alloy substrate by simple hydrothermal
method, with low surface energy modification and lubri-
cant injection. The lubricant was locked in the rough struc-
ture of the SHS to form the SLIPS, so the water droplet can
easily slide on the SLIPS with a small Sliding Angle (CA)
about 3˚. And the SLIPSs showed excellent mechanical
and chemical stability, whether under high shear condition
or in acidic/alkaline solutions. Furthermore, we conducted
a series of tests on the samples, and the results showed that
compared with the original surface and SHS, SLIPS had
better anti-corrosion, anti-fouling and anti-icing proper-
ties. Therefore, building SLIPS on the Al alloy substrate
can improve its performance, which is of great help to
expand its practical application and extend its life.
2 Experiments
2.1 Materials
The Al substrates (AA6061 alloy) were purchased from Shang-
hai Haocheng Metal Co. Ltd. China, and they were cut into
2cm × 2cm pieces. Stearic Acid (STA, CH3(CH2)16COOH)
purchased from Guangdong Province Fine Chemical Engi-
neering Technology Research and Development Center. Zinc
nitrate hexahydrate (Zn (NO3)2·6H2O, 99.0%) was obtained
from Tianjin Fangda Chemicals Co. Ltd. Ammonium nitrate
(NH4NO3) was supplied from BEIJINGSHIHONGXING-
HUAGONGCHANG, China. Ammonia (NH3·H2O), Dime-
thyl silicone oil (H201-100), and NaOH were all of analytical
grade, and were supplied by Sinopharm Chemical Reagent Co.
Ltd. Ethanol was purchased from Lianlong Bohua (Tianjin)
Medical Chemicals Co., Ltd. All the reagents were of analyti-
cal grade and used as received without further purification.
Deionized Water (DI) was used throughout the experiment.
2.2 Preparation ofSlippery Surface
The samples were prepared based on the previous method
[25]. Firstly, the Al alloy plates were sequentially abraded
with emery sand paper of grades 800, 1200, and 1500, cleaned
ultrasonically in ethanol and DI water successively. The pre-
treated sample was named as Bare. To remove the oxide film
on the Bare surface, the abraded Al alloy plates were etched in
0.1M NaOH for 120s at room temperature. And then the sam-
ples were ultrasonically cleaned with DI water and dried in air.
Secondly, the Bare was vertically immersed in a mixed
solution of 0.05M Zn (NO3)2 and 0.3M NH4NO3. The pH
was controlled to 6.5 by 1.0 wt% NH3·H2O. The hydrothermal
reaction was performed under hydrothermal treatment (85°C,
12h). After that, the samples were washed by ethanol and
dried in air naturally. The sample obtained by hydrothermal
process is named as Layered Double Hydroxide (LDH).
Thirdly, the prepared samples were immersed in 0.05M
STA/ethanol at 60°C for 6h and then dried in air at room
temperature. The obtained samples were denoted as SHS.
Finally, about 50 µL dimethyl silicone oil was used to lubri-
cate the as-prepared SHS. On the spin coater, spun coating at
500rpm for 30s to spread the lubricant evenly on the SHS,
and then threw out the excess lubricant at 1000rpm for 30s.
And the final product was labelled as SLIPS.
2.3 Mechanical andChemical Stability Tests
The mechanical and chemical stability test of the samples
was tested into three parts. (i) In the lubricant retention
capacity test, we compared the oil-locking ability of the
LDH and SLIPS, samples (LDH/oil, SLIPS) were rotated
Slippery Surface withPetal‑like Structure forProtecting Al Alloy: Anti‑corrosion,…
1 3
at different spin rates ranging from 1000 to 5000rpm for
10s to detect the mass variations. (ii) The CAs and SAs of
droplets with different pH (pH from 1 to 14) on the sam-
ple surfaces were measured. (iii) The CAs and SAs of the
samples were measured after immersion in 0.1M HCl and
NaOH solution for 10min to explore the chemical stability
of the samples.
2.4 Electrochemical Corrosion Test
The corrosion resistance of the samples was determined
by three-electrode electrochemical workstation with 3.5
vt% NaCl aqueous solution as electrolyte at room tempera-
ture. The platinum plate was used as the counter electrode,
CHI150 Saturated Calomel Electrode (SCE) as the reference
electrode, and the working electrode was the prepared sam-
ple. The polarization curves were obtained at the scanning
rate of 5mV∙s−1 from − 0.3 to 3V versus the open circuit
potential. The parameters of corrosion potentials (Ecorr)
and corrosion current density (Icorr) were obtained by Tafel
extrapolation method. Each sample was measured at least
three times.
2.5 Anti‑fouling andAnti‑icing Experiments
In the anti-fouling experiment, we selected several common
drinks (including milk, tea, coffee and cola) to test the anti-
fouling ability of the samples. Test at room temperature with
the liquid evenly stirred.
During the anti-icing experiment, about 15mL of water
was put into the culture dish, the treated side of different
samples (Bare, SHS and SLIPS) contacted with the water
surface, and then the culture dish was placed in the refrigera-
tor at − 10°C to observe the changes of the sample surfaces.
2.6 Characterization
All sample morphologies were characterized by field-
emission Scanning Electron Microscope (SEM, QUANTA
FEG 650). The apparent Contact Angles (CAs) and Slid-
ing Angles (SAs) were measured at room temperature by
a JC2000D goniometer with a 10 µL droplet. The chemi-
cal composition was analyzed via Fourier Transform Infra-
red spectroscopy (FTIR, Thermo Scientific Nicolet iS10).
X-ray Photoelectron Spectroscopy (XPS, Thermo Scientific
ESCALAB 250Xi) was used to characterize the quantita-
tive elemental composition. The contents of the chemical
elements were characterized via Energy Dispersive Spec-
troscopy (EDS, JSM-5600LV). The surface roughness of the
samples was measured on a 3D non-contact surface profiler
(KLA-Tencor MicroXAM-800).
3 Results andDiscussion
3.1 Surface Characterization
In this work, we constructed SLIPS with petal-like structure
on Al alloy substrate by a simple hydrothermal method. The
manufacturing process was shown in Fig.1. In brief, the
pretreated Al alloy was immersed in the mixed solution of
0.05M Zn (NO3)2 and 0.3M NH4NO3, then the pH of the
solution was adjusted to 6.5, the reaction was carried out in
an autoclave at 85°C for 12h. At this time, the surface of
Al alloy was covered with LDH film. And then the sample
was modified with ethanol/STA solution at 60°C for 6h to
obtain SHS. Finally, dimethyl silicone oil was injected into
the SHS to obtain SLIPS.
As we all know, the construction of superhydrophobic
surfaces requires a certain surface roughness and low sur-
face energy. In this work, the LDH film was constructed on
aluminum alloy by hydrothermal reaction. After modifica-
tion with stearic acid, carboxyl groups and metal ions form
complexes on the surface [26], which further increased the
roughness of the surface and reduced the surface energy to
obtain the superhydrophobic surface, as shown in Fig. S1.
Besides, we characterized the 3D surface profiles of the sam-
ples and measured their roughness. The surface roughness of
Fig. 1 Schematic illustration of
the formation of the SLIPS
Al alloy
J.Huang et al.
1 3
Bare, LDH and SHS are 0.018µm, 0.175µm and 1.63µm,
respectively (Fig. S2). The results show that STA modifica-
tion has great influence on the surface morphology, increases
the surface roughness of the sample and provide enough
space for oil injection.
The Fig.2a–d shown the SEM and water contact angle
images of the samples under different processes. Figure2a is
the surface of the Al alloy after pretreatment, we can observe
that there are scratches left by sandpaper rubbing on it. And
the surface of bare Al alloy is hydrophilic with a water con-
tact angle of 58°. After the hydrothermal reaction, the Al
alloy surface is covered with LDH film. The water contact
angle increases with the increase of surface roughness, but
it still shows hydrophilicity. The water contact angle of the
LDH film is 83° (Fig.2b). Figure2c and d show the LDH
modified by ethanol/STA solution at different magnification.
We can clearly see the petal-like structures on the Al alloy
surface in Fig.2d. As shown in Fig.2c, after modified with
ethanol/STA solution, the water contact angle of the sample
is about 155°, showing excellent superhydrophobicity. Since
the surface tension of silicone oil is lower than that of water,
silicone oil is easier to wet on superhydrophobic surfaces.
When silicone oil was injected into the SHS, an oil film
can be formed on the surface, and the petal-like structure of
the SHS can lock the lubricating oil to reduce its loss, thus
ensuring the stability of the SLIPS.
The water contact angle of SLIPS is 100° and the water
sliding angle is 3° (Fig.2e and f). The dynamic behavior was
taken every 15s. In addition, to explore the smooth charac-
teristics of the SLIPS, we also measured the CAs and SAs
of different liquids including oil-in-water on the SLIPS (Fig.
S3). It turns out that liquid not limited to water (N-hexane-
in-water, Oleic acid, Glycol, Ethanol and Diesel-in-water)
can slide at a low SA on SLIPS. The above results are mainly
attributed to the continuous lubricant layer of SLIPS, indi-
cating that SLIPS has excellent smoothness.
The FTIR spectrum of samples are shown in Fig.3a,
due to the stretching and bending vibrations of hydroxyl
groups, the broad peaks at 3402 and 1639.4 cm−1 appear
on the spectrum [27]. The peaks at 1332.7 and 821.45 cm−1
are from NO3, indicating that the LDH film is success-
fully formed on the Al alloy substrate after hydrothermal
reaction. At 2916 and 2846.8 cm−1, SHS has the stretching
vibration bands of C–H [28]. And the peaks that occurred
at 1537.2 and 1396 cm−1 are due to the asymmetric and
symmetric vibrations of COO groups [29]. According to
the analysis of the FTIR, it can be concluded that modifi-
cation of LDH film by STA has achieved nice results. As
illustrated in Fig.3b and c, the chemical compositions were
also analyzed by the XPS spectrum to verify the element
types of on the SHS. As shown in the Fig.3b, the Al peak
is not displayed, probably because Al is covered by other
elements or the Al peak intensity is too weak. Figure3c
is the C 1s spectra. The fitted peaks at 284.7, 285.1, and
288.7eV belonged to −CH2, −CH3 and O=C−O groups of
the STA [25, 30]. These results further demonstrate that the
hydrophobic groups of STA are grafted into LHD films to
form SHS. Furthermore, the EDS results indicated that SHS
has high content of C element (Fig. S4). All the above results
indicate that SHS is obtained after STA modification, which
lays the foundation for the fabrication of SLIPS.
3.2 Chemical andMechanical Properties
The chemical and mechanical properties are important
criteria to evaluate the quality of materials. Which has a
significant impact on whether the material can be can be
mass-produced and applied [31]. In practical applications,
metal materials are inevitably used in harsh environments,
so stable chemical and mechanical properties are extremely
important for Al-based SLIPS. Therefore, we explored the
effects of high shear force on the oil storage capacity of
Fig. 2 SEM images of a Bare, b
LDH, c SHS, d high magnifica-
tion SHS, e the CA of SLIPS
and f dynamic behavior of a
water droplet on the SLIPS
Slippery Surface withPetal‑like Structure forProtecting Al Alloy: Anti‑corrosion,…
1 3
samples and different pH solutions, acid and alkaline solu-
tions on SLIPS.
For the exploration of the mechanical properties of the
SLIPS, we mainly focus on oil retention capacity. To apply
a shearing stress on the samples, LDH/oil and SLIPS were
placed on a spin-coater and rotated at different spin rates
ranging from 1000 to 5000rpm for 10s to detect the vari-
ations in weights. Then we test the oil-locking ability of
the samples by the amount of residual silicone oil on the
surfaces (Δm = quality after centrifugal − Initial weight).
The initial condition of the samples was shown in Table1
and the test results were shown in Fig.4a. According to the
Table1, after the completion of silicone oil injection, the
average weight of SLPS increased by about 0.0358g and
LDH gained about 0.0108g. We preliminarily believe that
the oil locking ability of slips is stronger than that of LDH.
And then we measured the quality of the samples at differ-
ent spin rate, it is clear that the amount of oil retained on
the SLIPS is much higher than that of the LDH at different
speeds. Finally, after 5000rpm, LDH only retained about
18.44% of the oil while the SLIPS kept about 43.06%. The
results indicated that SLIPS showed preferable lubricant
retention ability relative to LDH, which can be interpreted
from the point of surface morphology and structure, as men-
tioned above.
As shown in Fig.4b, the contact angle of droplets with
different pH value on the SLIPS changes little. This result
shows that the oil film on the slippery surface has nice resist-
ance to H+ and OH. This is mainly due to the stable chemi-
cal properties of silicone oil. With the increase of the con-
centration of H+ and OH, the sliding angle of water droplets
on the SLIPS also increased slightly, but the sliding angle
was still less than 10°. In general, the oil film on the slippery
surface can prevent ions in the solution from destroying the
substrate surface, so contact angle and sliding angle of the
SLIPS do not change much under different pH values [32].
To further verify the chemical stability of the SLIPS, we
immersed the SLIPS and SHS in 0.1M HCl and NaOH solu-
tions respectively for different times to observe the changes.
In acidic and alkaline environments, the change results of
CA and SA between the SLIPS and SHS were shown in
Fig.4c, d and Fig. S5a. With the increase of immersion time,
the CA of SHS decreased gradually, whether in acid solution
or alkaline solution. Moreover, the CA of SHS decreased
more rapidly in acidic environment, the reason may be that
the surface of SHS is composed of layered double hydrox-
ides, and LDH is easier to combine with hydrogen ion than
hydroxyl ion. Fig. S5b shows the picture of the SHS after
292290 288 286284 282 280
284.7 eV
Intensity (a.u)
Binding energy (eV)
288.7 eV
285.1 eV
C 1s
1200 1000800 600 400200 0
Zn 2p
O 1s
Intensity (a.u)
Binding energy (eV)
C 1s
40003500 3000 25002000 1500 1000
Wavenumer (cm
% Transmittance
LDH film
Fig. 3 a FTIR spectra of the LDH film and SHS, b XPS and c C 1s
spectra of SHS
Table 1 The initial condition of the samples
Samples Initial weight (g) Silicone
LDH 1.0133 1.0241
SLIPS 1.0176 1.0534
J.Huang et al.
1 3
corroded by acidic and alkaline solution. It is clear that the
surface damage was more severe after soaking in HCl solu-
tion. Obviously, the SHS cannot effectively resist the cor-
rosion of the substrate by acid or alkali solution. On the
contrary, as shown in the Fig.4, the CAs of the SLIPSs
did not change much after soaking in the solution. With the
increase of immersion time, the SAs of the SLIPSs increases
gradually, but the overall SAs were less than 10°. It indicates
that the oil film on the SLIPS had certain resistance to the
corrosion of acid and alkali solution in a short time. In short,
the SLIPS is protected by the oil film, so it has better chemi-
cal and mechanical stability than SHS.
3.3 Anti‑corrosion Ability
To study the corrosion resistance of the SLIPS, electrochem-
ical corrosion tests were carried out in NaCl solution and
compared with SHS and Bare. The potential polarization
curves were obtained by the assistance of a three-electrode
electrochemical workstation, and the corrosion current
(Icorr) density and corrosion potential (Ecorr) were obtained
via the Tafel extrapolation method. The data obtained from
the electrochemical corrosion test were selected to plot the
curve, and the results were shown in Fig.5. As shown in
Table2, the corrosion potential (Ecorr) and corrosion cur-
rent (Icorr) density of the group were displayed. The Icorr
and Ecorr of Bare, SHS and SLIPS were 7.871 × 10−6A,
3.585 × 10−6A, 1.247 × 10–6 A and − 0.752V, − 0.736V,
− 0.684V, respectively. Generally, samples with superior
corrosion resistance have higher corrosion potential (Ecorr)
and lower corrosion current (Icorr) [33]. Therefore, this data
indicate that SHS is superior to Bare, while SLIPS is better
than SHS in corrosion resistance. It should be noted that low
current density comes from the oil film, which makes the
Time (min)
Contact angle )
Sliding angle )
Time (min)
Contact angle )
(c )
Sliding angle )
ph value of water
Contact angle )
Sliding angle )
1000 2000 3000 4000 5000
m (g)
Spin Rate (rpm)
Fig. 4 a Oil loss of samples at different spin rates. b CAs and SAs of SLIPS with different pH values. c CAs and SAs of SLIPS after immersion
in 0.1M HCl solution for different time. d CAs and SAs of SLIPS after immersion in 0.1M NaOH solution for different time
Slippery Surface withPetal‑like Structure forProtecting Al Alloy: Anti‑corrosion,…
1 3
SLIPS have excellent corrosion resistance. The oil film insu-
lates the contact between the substrate and the NaCl solution
to protect the Al alloy. The result showed that lubricant has
good physical barriers for protecting the Al alloy substrate
from corrosion.
3.4 Anti‑fouling andAnti‑icing
In our daily life, the surface with antifouling ability has a
huge impact, and it can improve the application range of
materials [34]. Here, to compare the anti-fouling capability
of the samples, they were immersed in comment different
liquids (including coffee, tea, milk and cola) for 10s then
removed. It is noteworthy that all the liquid used for the test
is thoroughly stirred to uniform. The test results are shown
in Figs.6a–d, after soaking in coffee, some liquid remains
on the Bare, and the SHS can still be kept clean due to the
water repellency (Fig. S6). Unexpectedly, the SLIPS can also
keep clean after soaking in coffee (Fig.6). The same effect
was found in tea, milk and cola tests, the SHS and the SLIPS
remained as clean as at the beginning while the surface of
Bare had some residues (Figs.6b–d). Remarkably, because
of the existence of oil film, the SLIPS can repel most liquids
with high surface tension, and the liquid can slide readily. In
short, the SLIPS has slippery and hydrophobic properties,
and liquid is not easy to remain on its surface, so it reveals
fine anti-fouling performance. And the SLIPS is superior to
SHS in the above-mentioned performances, thus, SLIPS may
be used in anti-pollution in various industries in the future,
such as construction, shipbuilding, automobile manufactur-
ing, and so on.
-1.0 -0.9 -0.8 -0 .7 -0.6 -0.5 -0.4
Fig. 5 Electrochemical corrosion tests of the Bare, SHS and SLIPS
Table 2 Corrosion characteristics of the samples in 3.5 wt% NaCl
3.5 wt% NaCl solution
Samples Ecorr (V) Icorr (A)
Bare − 0.752 7.871 × 10–6
SHS − 0.736 3.585 × 10–6
SLIPS − 0.684 1.247 × 10–6
Contact angle )
Icing/drawing cycle number
Fig. 6 A Series of anti-fouling tests testified the self-cleaning abil-
ity of the SLIPS (left) and SLIPS (right) immersed in a coffee, b tea,
c milk and d cola. e The adhesion of different samples (Bare, SHS
and SLIPS) to the ice surface when water freezes. f Changes in the
surface of the samples (Bare, SHS and SLIPS) after a long period of
freezing. e CAs of SHS and SLIPS after freezing and drawing with
different cycles in the anti-icing test
J.Huang et al.
1 3
Moreover, ice accretion has a serious impact on the usage
life of equipment and the application of materials, result-
ing in huge disaster and economic losses [35]. Therefore,
improving the ice resistance of materials is also a hot topic
for researchers. Herein, the anti-icing performances of
Bare, SHS, and SLIPS were tested. Under the condition of
− 10°C, 15mL water was injected into the culture dish, and
then put the treated sample surface in contact with the water
surface until the water freezes. The adhesion effect between
the sample and the ice surface was compared. As shown in
the Fig.6e, Bare and HSH were firmly adhered to the ice
surface, while SLIPS was easier to remove from the ice sur-
face than them. The reason for this phenomenon may be that
under low temperature conditions, the moisture adhering to
the solid surface instantly freezes and sticks to the ice sur-
face. However, SLIPS insulates the contact between water
and the substrate due to the existence of the oil film, and
the water molecules on the oil film are not easy to form ice
nuclei and the ice crystals grow slowly, making it difficult to
adhere to the ice surface [36, 37]. The CAs during freezing
and drawing cycles were measured and reflected in Fig.6g.
In the icing/drawing test, due to the destruction of SHS and
the lubricant oil loss of SLIPS, they all lost their low sliding
angle. The CA of SHS drops to about 110° after five cycles
for icing/stretching, while SLIPS can maintain a relatively
stable CA due to the protection of the oil film. Furthermore,
the petri dish was left in the refrigerator overnight, after a
long time of freezing, there was almost no change on the
slips, but slight damage on Bare and SHS (Fig.6f). Thence,
there is no doubt that SLIPS shows better anti-icing than
Bare and SHS.
4 Conclusion
In summary, the multi-functional SLIPS have been con-
structed on Al alloy by a simple hydrothermal method,
stearic acid modification and dimethyl silicone oil lubrica-
tion, successively. The experimental results showed that the
three main factors of SLIPS were surface roughness, low
surface energy and infused lubricant oil. The SLIPS based
on Al alloy not only revealed significant hydrophobicity, but
also has low slip angle, on which water droplets can slide at
5°. In addition, the stability of the SLIPS was also attractive.
In the physical and chemical properties experiments, 43.06%
of the lubricating oil can still be stored on the SLIPS after
high shearing force, and it can maintain a low sliding angle
after strong acid/alkali immersion.
Furthermore, the excellent anti-corrosion, anti-fouling
and anti-icing performance of SLIPS are of great help to
prolonged the service life of Al alloys and expand their prac-
tical application range. Moreover, SLIPS has broad appli-
cation prospects in the fields of automobile, shipbuilding,
architecture and so on. It is hoped that this paper can provide
some reference for expand the practical application range
Supplementary Information The online version contains supplemen-
tary material available at https:// doi. org/ 10. 1007/ s42235- 021- 00124-6.
Acknowledgements This work was financially supported by the
National Natural Science Foundation of China (no. 51735013 and
51905520)andthe PreResearch Program in National 14th FiveYear
Plan (grant number 61409230614).
Conflict of interests The authors declare that they have no known com-
peting financial interests or personal relationships that could have ap-
peared to influence the work reported in this paper.
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Full-text available
Slippery liquid-infused porous surfaces (SLIPS) have emerged as a unique approach to creating surfaces that can resist fouling when placed in contact with aqueous media, organic fluids, or biological organisms. These surfaces are composed of essentially two components: a liquid lubricant that is locked within the protrusions of a textured solid due to capillarity. Drops, immiscible to the lubricant, exhibit high mobility and very-low-contact-angle hysteresis when placed on such surfaces. Moreover, these surfaces are shown to resist adhesion to a wide range of fluids, can withstand high pressure, and are able to self-clean. Due to these remarkable properties, SLIPS are considered a promising candidate for applications such as designing anti-fouling and anti-corrosion surfaces, drag reduction, and fluid manipulation. These collective properties, however, are only available as long as the lubricant remains infused within the surface protrusions. A number of mechanisms can drive the depletion of the lubricant from the interior of the texture, leading to the loss of functionality of SLIPS. Lubricant depletion is one challenge that is hindering the real-world application of these surfaces. This review mainly focuses on the studies conducted in the context of enhancing the lubricant retention abilities of SLIPS. In addition, a concise introduction of wetting transitions on structured as well as liquid-infused surfaces is given. We also discuss, briefly, the mechanisms that are responsible for lubricant depletion.
Ti6Al4V alloy with excellent mechanical, physical, and chemical properties is now widely used in marine, aerospace, and biomedicine industry. Endowing Ti6Al4V alloy with better surface performances is of great significance and value. Herein, a convenient and commercial nanosecond laser etching method is utilized to fabricate a novel multiscale micro/nano porous structure based on Ti6Al4V alloy. Following the modification of the fluoroalkylsilane and the infusion of silicon oil, the slippery liquid‐infused porous surface (SLIPS) is successfully obtained. The wettability is studied in detail and indicates the SLIPS possesses excellent sliding property and hydrophobicity. The volume of the droplet and sample temperature are confirmed to have some significant impact on the sliding angles. Accordingly, a variety of liquids are able to slide down the tilted SLIPS (15.9°), indicating that the as‐prepared SLIPS demonstrates extraordinary liquid‐repellent ability. In addition, the multiscale micro‐/nanoporous structures can lock the silicon oil firmly and form a stable oil film on the surface, so the SLIPS also shows desirable self‐cleaning, self‐healing, and stability properties. Based on the study, it is promising that the SLIPS as‐prepared may expand the practical application of conventional Ti6Al4V alloy materials.
Metal materials are susceptible to the influence of environmental media, and chemical or electrochemical multiphase reactions occur on the metal surface, resulting in the corrosion of metal materials which can...
Inspired by the non-contact nature offered by the superhydrophobic surfaces of living creatures in nature, the superhydrophobic and slippery liquid-infused porous surfaces (SLIPS) have been fabricated to meet the engineering problems including metal corrosion. In this research, we fabricate the hydrophobic, superhydrophobic, hydrophobic lubricant-infused surface (H-SLIPS), and superhydrophobic lubricant infused surface (SH-SLIPS) onto aluminium alloy surfaces and explored their anti-corrosion properties. The hydrophobic and superhydrophobic surfaces are fabricated by hot-water treatment and silicon oil grafting onto the plain and superhydrophilic surface created by hot water treatment of the chemically etched aluminium surface, respectively. The corresponding SLIPS are fabricated by infusion of the silicone oil onto the prepared hydrophobic and superhydrophobic surfaces. Although the superhydrophobic surface exhibits self-cleaning behavior, the SLIPS shows excellent self-healing properties. In addition, the H-SLIPS shows better lubricant layer stability compared to the SH-SLIPS. The corrosion resistive and electrochemical impedance studies illustrate that H-SLIPS surfaces exhibit excellent anti-corrosive properties as compared to other substrates and show long-term performance, even after 30 days. Thus, the study illustrates that H-SLIPS performs better and the infused oil stability is a critical factor for applications like anti-corrosion properties.
Superhydrophobic surfaces (SHS) and slippery lubricant-infused porous surfaces (SLIPS) attract great attention due to their multiple properties in both industries and our daily lives. Here, we first fabricated the SHS with micro-scale flower-like structures composed of nano-sheets on pipeline steel substrate. Then, we obtained the SLIPS by spin-coating lubricant into gaps of micro-scale flower-like structures, with the air still trapped among gaps of nano-sheets. The SLIPS shows excellent liquid repellency as the SHS. The SLIPS also shows stability after the scour of flowing water. These results of polarization curves (Tafel) and electrochemical impedance spectroscopies deduced the SLIPS with better and more stable anti-corrosion property than the SHS. Compared with the SHS, the lack of attachment and CaCO3 on the SLIPS indicates that the SLIPS demonstrates better anti-fouling and anti-scaling properties than the SHS. Moreover, the SLIPS shows promising wear resistance under the abrasion simulated by sandpaper compared with the SHS. Notably, the air trapped among nano-sheets is conducive to the lubricant flowing to the surface quickly, exhibiting spontaneous self-healing in atmosphere, even if part flower-like structures of the SLIPS subject to damage with the lubricant consumed after scratched.
Full-text available
Superhydrophobic (SHP) surfaces had promising application in anti-icing field. In this work, ZnO SHP surfaces were prepared on aluminum alloy by radio frequency (RF) magnetron sputtering. The structure, chemical composition, morphology, wettability of the SHP surfaces were investigated by using corresponding methods. The anti-frosting/anti-icing performance of the ZnO SHP surfaces were investigated. Morphology of surfaces showed that sputtering time affected the surface morphology of the ZnO surfaces. When the sputtering time was 15 min, the rough structure exhibited excellent anti-frosting/anti-icing property due to the exceptional superhydrophobicity and self-transfer behavior at subzero temperature, which composed by densely gathered nanoclusters. The freezing of water droplets was delayed for about 2 h, and frosting was delayed for approximately 5 h at the temperature of −10 °C. The SHP surfaces could efficiently enhance the anti-icing property in glaze ice. Meanwhile, the as-prepared ZnO SHP surfaces displayed a low ice-adhesion strength of 12 ± 4.7 kPa. However, the structure with large undulation and pore space reduced the anti-frosting/anti-icing property of the SHP surface. This work provided a direction for the design and preparation of anti-icing surfaces for power transmission lines.
In this article, a novel and facile method is used to construct superhydrophobic surfaces on aluminum alloys. A solution of aluminum chloride hexahydrate and N-dodecyltrimethoxysilane (DTMS) in ethanol was used as the electrolyte solution. The hydrolysis of DTMS was accelerated during the electrodeposition process, and the hydrolysate was bonded to a pretreated aluminum surface. The prepared aluminum alloy sample exhibits both superhydrophobicity (the surface water contact angle reached 155°) and excellent corrosion resistance. The inhibition efficiency of this sample is as high as 99.9% in 3.5 wt % NaCl solution, which remains at 98% even after 30 days of immersion. Thus, our fabrication can be well applied to the field of marine corrosion protection. Therefore, the working mechanism was discussed by confocal Raman microspectroscopy (CRM). In addition, the investigation by CRM and electrochemical impedance spectroscopy (EIS) also indicates that superhydrophobic samples show good stability in NaCl solution. The fabrication method can inspire new ideas for the construction of superhydrophobic aluminum alloys in the marine environment.
Zinc and its alloys have played an important role in the fields of ship manufacturing, construction industries as well as our daily life. However, their applications are largely restricted due to the poor performances under the extreme conditions. Meanwhile, the slippery liquid-infused porous surface (SLIPS) has been widely applied owing to their excellent water repellent, anti-corrosion and anti-icing properties. Herein, a SLIPS based on ZnO nanotube substrate was fabricated via a hydrothermal process, low surface energy modification and lubricant oils infusion, successively. The slippery Zn surface showed a low sliding angle of about 5° to water droplet after infusing lubricants into vacancy among ZnO nanotubes (NTs). More important, the slippery Zn surface exhibited superior omniphobicity for liquids with a wide range of surface tension. Furthermore, the fabricated SLIPS exhibited outstanding slippery stability after several physical and chemical tests such as scratching, wiping and strong acid/alkali immersion. In addition, the anti-corrosion, anti-icing and anti-fouling properties have importance significance for extending the practical applications of slippery Zn surface. Therefore, the slippery Zn surface is expected to be an efficient method to enhance the physical and chemical stability, anti-corrosion, anti-icing and anti-fouling properties of zinc and its alloys and can expand their applications in anti-fouling & self-cleaning of automobile, ship and construction industries under extreme environments.
How to prepare multifunctional surfaces with high nucleation density and fast droplet removal during droplet condensation remains a challenge. It is believed that water droplet on superhydrophobic surface (SHS) in Cassie state is inclined to convert to Wenzel state under high pressure or high-humidity conditions, which results in the pinning effect. Hence, it is necessary to form thermodynamically stable lubricant-infused surfaces (LISs) applied in water condensation, especially under extreme working conditions. In this work, CuO LISs with two different morphologies (chrysanthemum-like and dandelion-like structures) in slippery state were prepared and the effect of surface morphology on water harvesting behavior was investigated. The results indicated that the dandelion-like CuO consisting of nanoneedles exhibited inferior water harvesting behavior compared to chrysanthemum-like CuO consisting of nanolamellas due to worse lubricating oil loss. Furthermore, the strong intermolecular forces between the perfluoropolyether (PFPE) lubricating oil and perfluorodecanethiol (PFDT)-modified coating resulted in durable lubricating layer, which exhibited favourable anti-icing, anti-corrosion and liquid repellency even under strong acid and alkali conditions, high shear force rate up to 7000 rpm and long-time ultraviolet light irradiation for 12 h. This work paves the path for efficient droplet nucleation and removal, which has potential in water harvesting in arid regions and water condensation for power generation.
Water is recognized as a contaminant in lubricating oils. Recently, interfacial materials with special wettability are broadly developed for oil-water separation. However, solving lubricating oil failure caused by water remains a challenge. Here, a robust superhydrophobic membrane is presented to effectively remove water in lubricating oils to recover their lubricating capability. Compared to pure lubricating oils without or with an additive, the lubricating oils collected from their emulsions using the superhydrophobic membrane have equivalent friction coefficient and wear volume, which are much lower than that of lubricating oils contaminated by water. Water in lubricating oils accelerates oxidation of metallic substrates and wear corrosion. Moreover, the metallic ions dissolved in water-containing lubricating oils induce catalytic dehydrogenation of lubricating oils, leading to the deposition of a good deal of carbon-based wear debris. Importantly, the prepared membrane shows steady performance in regard to extreme water repellency, high-efficiency purification of lubricating oils, and low wear volume even after harsh mechanical damage. Robust interfacial materials have potential advantages in practically solving lubricating oil failure caused by water.
Despite decades of researches, superhydrophobic surfaces rely on a stable air layer plagued with problems, such as poor pressure stability, inability to self-heal, and failure to repel organic liquids or...
Shortage of water resources and deterioration of water quality are becoming more and more serious today. Inspired by Namib Desert beetles, scientists designed biomimetic fog collection materials to get fresh water. Given that the overview of this field is limited and mainly concerned with preparation and application. In this paper, we focused on the water collection efficiency of water collection surface inspired by beetle. And discussed their influence on water collection efficiency from three aspects: surface wettability, surface structure and surface pattern distribution.
In this study, copper oxide nanoribbons were fabricated on a Cu substrate by a simple liquid-solid reaction. The superhydrophobic copper oxide surface was formed by the immersion of the sample in an ethanol solution of stearic acid. The water contact angle on this surface was 153.6°. A slippery copper oxide surface was prepared by the immersion of superhydrophobic copper oxide in DuPont Krytox. Electrochemical measurement revealed that the corrosion resistance of the slippery surface was more stable than those of bare Cu and superhydrophobic surface. The inhibition efficiency reached up to 92.68%. This study provided a possible method for preventing copper corrosion.
Inspired by Nepenthes pitcher plants, slippery liquid-infused porous surfaces (SLIPS) have recently attracted increasing attention for directional transport and movement manipulation of water droplets. Nevertheless, infused lubricants are generally instable and easy to deviate from such surfaces during applications, resulting in the lost control on the fog capture and motion of droplets as well as serious risk of water safety. Here, a highly stable SLIPS with improved lubricant-storage is developed through the structure design of synergistically constructing regular micro-pincushion and nanoparticles. Notably, on the basis of the micro-structure, the presence of nano-architecture shows great contribution to obviously increased capillary force as well as suppressed lubricant loss during water collection. Featuring the stable surface-slippery property, the biomimetic SLIPS displays well maintained dropwise coalescence of water from fog and efficient water harvesting performance. The water collection efficiency is as high as 852 mg cm-2 h-1 and is stable within continuous 20-h application. This fundamental illustration of structural synergism can be further applied to construct more new water manipulation and harvesting platforms with stably slippery surfaces/interfaces.
This work is focused on the development of a facile strategy to fabricate superhydrophobic coatings, which are characterized with lower water freezing temperature and lower ice adhesion. First, a kind of polyacrylic acid (PAA) based resin material is synthesized as the coating-matrix. Then the functionally-modified SiO2 nanoparticles are added to regulate the surface morphology for obtaining the ideal superhydrophobicity. The as-synthesized resin coatings possess strong bonding strength with metal substrate, and the surface hierarchical morphologies (10 wt% SiO2 nanoparticles) induce the robust superhydrophobicity with a high water contact angle of 152°. Also, the superhydrophobic coatings are endowed with high icephobicity, and the freezing temperature of reference water droplet is reduced to −20.33°C comparing with that (−13.83°C) on the coatings without additive nanoparticles. Furthermore, the ice adhesion strength on the superhydrophobic coatings is only 250 kPa, exhibiting the great ability of ice repellence.