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Article

Preparation of Barium Europium Phosphate and Its Performance in Acrylic Resin Anti-Corrosion Coating

by
Xuying Deng
†,
Jihu Wang
†,
Shaoguo Wen
*,
Jiale Zhao
,
Xue Zhang
,
Yicheng Zhao
and
Zhiying Deng
College of Chemistry and Chemical Engineering, Shanghai University of Engineering Science, Shanghai 201620, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Polymers 2025, 17(14), 1966; https://doi.org/10.3390/polym17141966
Submission received: 26 May 2025 / Revised: 8 July 2025 / Accepted: 9 July 2025 / Published: 17 July 2025
(This article belongs to the Section Polymer Analysis and Characterization)
Browse Figures
Versions Notes

Abstract

Acrylic resin is a polymer with strong crosslinking density and strength, and it is commonly used as a matrix in water-based coatings. Barium europium phosphate (Ba3Eu(PO4)3) is a novel functional filler that is expected to provide anti-corrosive effects to coatings. In this study, Ba3Eu(PO4)3 was prepared by the high-temperature solid-phase method and applied to acrylic anti-corrosion coatings. The influence of the molar ratio of reactants on Ba3Eu(PO4)3 purity was studied. The anti-corrosion performance of the coating was investigated. It was found that, when BaCO3:Eu2O3:(NH4)H2PO4 = 3:0.5:3 and the reaction was carried out at 950 °C for 1000 min, high-purity Ba3Eu(PO4)3 can be obtained, according to XRD and EDS tests. SEM shows that Ba3Eu(PO4)3 has good crystal morphology and a porous morphology. TEM revealed that its structure was intact. When Ba3Eu(PO4)3 was added to a relative resin content of 5 wt%, the anti-corrosion performance of the coating was the best after 168 h, with the lowest Tafel current density of 9.616 μA/cm2 and the largest capacitance arc curvature radius. The salt spray resistance test showed that the corrosion resistance of the 5 wt% Ba3Eu(PO4)3 coating was also the best, which is consistent with the results of the electrochemical test. Ba3Eu(PO4)3 as a pigment and filler can effectively improve the anti-corrosion performance of water-based industrial coatings.

1. Introduction

In recent years, with the rapid development of many fields, such as construction, transportation, petrochemicals, and hydropower, anti-corrosion coatings have entered a golden period of development. In 2023, the production of and demand for anti-corrosion coatings in China reached 8.913 million tons and 8.707 million tons, respectively. These coatings can be used to prevent and reduce huge economic losses and disasters caused by corrosion problems [1]. Coatings are a very economical and effective method of corrosion protection [2,3]. The interfacial adhesion and material composition of coatings are important indicators for the improvement of their corrosion reduction performance. According to the “14th Five Year Plan for China’s Coatings Industry” released by the China Coatings Industry Association [4], in order to protect the environment, it is recommended to use water-based resins with extremely low VOC content and to discard heavy metals, such as lead and chromium, from the fillers. Instead, fillers with functional or structural characteristics should be used to slow down the corrosion rate of coatings. The problem of corrosion control still needs to be addressed further [5,6,7,8].
Rare-earth phosphates are considered effective corrosion inhibitors for protecting metals and have been used to suppress the corrosion of different metal alloys [9]. The main reason is that rare-earth phosphates can not only refine the grain size on the surface of the substrate but can also improve the adhesion between the coating and the metal substrate, reduce the porosity of the coating, and thus enhance the corrosion resistance of the coating. Highly reactive trivalent rare-earth metal ions react with the matrix resin to obtain a substance with extremely strong bond energy, thereby further improving the corrosion and aging resistance of the substrate [10]. In addition to rare-earth cerium (Ce), there have also been many studies on rare-earth europium (Eu) in anti-corrosion applications. Li [11] modified the surface of organic compounds using the structural characteristics of vanadium oxide, neodymium oxide, and hexahydrate europium nitrate. The coating, prepared by mixing with nano-modified acetylene black material, had a continuous hydrophobic structure and strong adsorption ability, which can solve the problems of corrosion and detachment of rare-earth magnesium silicon aluminum surfaces. Amir [12] combined Eu2O3 with epoxy resin and found that the corrosion resistance of scratch coatings to saltwater erosion was significantly improved by about 57%. Therefore, the application of rare-earth europium in anti-corrosion coatings needs further investigation.
Ba3Eu(PO4)3 serves as an anti-corrosion filler for two primary reasons. Firstly, it introduces PO43− ions, which enhance the adhesion between the coating film and the substrate. Secondly, it incorporates rare-earth Eu3+ ions. These ions exhibit characteristic red (or other) warning colors under different UV excitation wavelengths. This luminescent behavior offers a theoretical basis for current research into self-warning and self-healing coatings. This article investigates the effects of different reaction ratios on the purity of Ba3Eu(PO4)3 synthesized by the high-temperature solid-phase method. The purity and elemental distribution of Ba3Eu(PO4)3 were analyzed through XRD and EDS. The microstructure and crystal structure were tested using SEM and TEM, and the pore diameter was calculated. Finally, the effects of different amounts of Ba3Eu(PO4)3 on the anti-corrosion performance of acrylic coatings were investigated using an electrochemical workstation and a salt spray machine.

2. Materials and Methods

2.1. Materials

Barium carbonate (BaCO3, AR) was purchased from Tianjin Jinhui Taiya Chemical Reagent Co., Ltd. (Tianjin, China). Europium oxide (Eu2O3, AR) and erbium oxide (Er2O3, AR) were purchased from Nanjing Chemical Reagent Co., Ltd. (Nanjing, China). Ammonium dihydrogen phosphate (NH4)H2PO4, AR) was purchased from Suzhou Furun Huagong Technology Co., Ltd. (Suzhou, China). Anhydrous ethanol was purchased from the National Pharmaceutical Chemical Reagent Co., Ltd. (Shanghai, China). Acrylic resin (industrial grade) came from Shanghai Qixiang Qingchen New Material Technology Co., Ltd. (Shanghai, China). The pH regulator (DMAE, industrial grade) was purchased from Hunan Youxin Material Technology Co., Ltd. (Hunan, China). The film-forming agent (alcohol ester 12, industrial grade) was purchased from Shandong Xinheng Chemical Co., Ltd. (Jinan, China). The anti-flash-rust agent (30% NaNO2, LR) was self-made in the laboratory. Dispersant 5040 (sodium polycarboxylate), defoamer C-15, and wetting agent G-033 were all industrial grade and came from Anhui Guangcheng New Materials Co., Ltd. (Chuzhou, China). HTK-3020 leveling agent (industrial grade) was purchased from Shanghai Hongtu Industrial Co., Ltd. (Shanghai, China). Ethylene glycol butyl ether (AR) was provided by Shanghai McLean Biochemical Co., Ltd. (Shanghai, China). Thickener WT-105A (industrial grade) was purchased from Shanghai Kaiyin Chemical Co., Ltd. (Shanghai, China). Distilled water was self-made in the laboratory. All of the above reagents were used as received.

2.2. Preparation of Ba3Eu(PO4)3

Using the high-temperature solid-phase method, BaCO3, Eu2O3, and (NH4)H2PO4 were weighed in a certain stoichiometric ratio (with mole ratios of 3:1:3, 3:0.7:3, and 3:0.5:3, respectively) and ground in an agate mortar for 30 min. The mixture was collected in a corundum crucible and transferred to a muffle furnace. It was preheated at high temperature for 1000 min at 950 °C, cooled to room temperature, crushed, ground, and sieved. It was calcined again at 950 °C for 1000 min, cooled down, and ground to obtain a white solid powder, which was the europium barium phosphate filler.

2.3. Preparation of Anti-Corrosion Coating

According to the formula in Table 1, DI water, DMAE, dispersant 5040, and defoamer were added into the material cylinder and stirred at 300 rpm for 10 min and the pH value was adjusted to around 8.5. Then, different amounts of Ba3Eu(PO4)3 (0 wt%, 1 wt%, 2 wt%, 3 wt%, 5 wt%) were mixed with DI water for 30 min before adding them to the drum. The speed was increased to 1000 rpm and stirred for 60 min. Subsequently, the rotating speed was reduced to 500 rpm and acrylic acid lotion and other additives were added and dispersed evenly for 15 min. Finally, ethylene glycol butyl ether, DI water, and WT-105A were mixed in a ratio of 1:1:1 to obtain the coating.
The tinplate was polished with 600-mesh sandpaper, wiped with deionized water, washed with absolute ethanol, and dried for use. The coating was applied to the tinplate using a wire rod and dried to form a film. The coating thickness was 100 ± 2 μm.

2.4. Characterization

The BRAGG110 X-ray diffractometer (Bruker, Karlsruhe, Germany) was used to analyze the crystal structure and purity of europium barium phosphate prepared by different molar ratios of barium, europium, and phosphorus. The testing conditions were Kα-rays from a Cu target, with a wavelength of 1.5405 nm. The scanning range and speed were 5–80° and 0.02°/s.
The microstructure of europium barium phosphate was observed using a ZEISS Gemini 300 scanning electron microscope (SEM) (ZEISS, Shanghai, China) and EDS/mapping spectroscopy was performed based on it to analyze the distribution of europium barium phosphate elements.
The morphology of europium barium phosphate was observed by using JEOL-2100F transmission electron microscope (TEM) (JEOL, Tokyo, Japan).
The corrosion status of the coating was evaluated by using CHI660E electrochemical workstation (CH Instruments, Inc., Huntington Beach, CA, USA). The electrochemical impedance spectroscopy (EIS) and Tafel polarization curve (Tafel) were plotted to analyze the corrosion resistance performance of the coatings. A 3.5 wt% NaCl solution was used as the electrolyte solution at room temperature.
The tinplate coating samples were placed in the CHY-7B salt spray test chamber for anti-corrosion testing for different resistance times according to ASTM-B117 [13]. The salt spray environment was 3.5 wt% NaCl solution.

3. Results and Discussion

3.1. XRD of Ba3Eu(PO4)3

Ba3Eu(PO4)3 was prepared by selecting BaCO3:Eu2O3:(NH4)H2PO4 in different molar ratios of 3:1:3, 3:0.7:3, and 3:0.5:3, respectively. The crystal phase structure was analyzed by XRD, and the experimental results are shown in Figure 1.
The standard peaks were simulated through software, and the peaks of the synthesized products with different molar ratios were compared. When the molar ratio of the substance was 3:1:3, there were more impurities, such as Ba3(PO4)2 and Eu2O3, which may indicate insufficient reaction. When the molar ratio of the substance was 3:0.7:3, there was still a small peak of Ba3(PO4)2. When the molar ratio of the substance was 3:0.5:3, there was a peak which was consistent with the standard peak. Compared with the standard PDF card of barium phosphate (25-0028), there was no Ba3(PO4)2 and Eu2O3 impurity peak at the crystal planes (111), (200), (220), and (311) [14]. This proved that the reaction was complete. The strong and sharp diffraction peaks indicated good crystallinity. The sample belongs to the monoclinic crystal system and matches with standard card JCPDS No. 29-0162.
The Scherrer equation D = kλ/β cosθ was used to calculate the crystallite size. λ was the X-ray wavelength, approximately 0.1541 nm (Cu Kα radiation). k was the shape factor. For amorphous crystals, the literature commonly assigns it a value of 0.89 [15,16,17]. β was the full width at half maximum (FWHM) of the sample’s diffraction peak, which needs to be converted into radians during the calculation process. The strongest peak at 2θ = 31.924° was used, and its β value was obtained from the analysis software. Among them, the FWHM was 0.089°, and the unit converted β value was about 0.0016. The calculated average crystallite size (D) was approximately 89.09 nm.
Based on the investigation of reactant molar ratios discussed in Figure 1, the optimal molar ratio for synthesizing pure Ba3Eu(PO4)3 was determined to be 3:0.5:3. Considering the thermal decomposition temperatures of the reactants, 950 °C was selected for calcination.
Figure 2 showed that the calcination time of 1000 min was strongly insufficient, and the majority of the product was Ba3(PO4)2. In contrast, the products calcined for 2000 min and 3000 min matched well with the standard diffraction peaks according to JCPDS No. 29-0162.

3.2. EDS of Ba3Eu(PO4)3

The elemental mapping images and EDS spectra of Ba3Eu(PO4)3 samples prepared with a molar ratio of 3:0.5:3 were analyzed by SEM testing. The experimental results are shown in Figure 3 and Figure 4.
From Figure 3, it can be seen that the surface of Ba3Eu(PO4)3 fluorescent powder particles is smooth, and Ba, Eu, P, and O elements were uniformly distributed in them.
Analyzing the EDS image of Ba3Eu(PO4)3 in Figure 4, it can be found that the Ba, Eu, and P mass fractions were 52.6%, 20.2%, and 8.8%. It was confirmed that the mole ratio of the substance was about 3:0.5:3. Eu2O3 reacted completely with BaCO3 and (NH4)H2PO4, which converted into Ba3Eu(PO4)3. The appearance of trace Er elements may be due to impurities in the raw materials.

3.3. Morphology of Ba3Eu(PO4)3

SEM was performed on Ba3Eu(PO4)3 prepared at the molar ratio of 3:0.5:3. The result is shown in Figure 5.
From Figure 5, it can be seen that the shape of Ba3Eu(PO4)3 was similar to a honeycomb-like pore structure, with pore diameters ranging from 284.48 to 1042.17 nm. Ba3Eu(PO4)3 synthesized by a high-temperature solid-phase method has the characteristics of a large specific surface area and high porosity, but there was an aggregation phenomenon. The main reason was the impact force released by a large amount of hot gases (CO2, NH3) during the reaction synthesis at high temperatures, resulting in the formation of more pores with irregular shapes.
Ba3Eu(PO4)3 prepared with a molar ratio of 3:0.5:3 was observed by TEM. The experimental results are shown in Figure 6.
From Figure 6a, it can be seen that the surface of Ba3Eu(PO4)3 was smooth, with some parts appearing light gray and the others appearing black. This indicated that the sample was composed of a combination of hollow and solid amorphous materials. Ba3Eu(PO4)3 particles prepared by the high-temperature solid-phase method become loose and expand at the outer edge due to the release of gas and heat. The local area (as shown in Figure 6b) was enlarged and the interplanar spacing between regions I and II was measured. The crystal plane spacing was 0.34 nm and 0.35 nm, respectively.

3.4. The Anti-Corrosion Performance of Ba3Eu(PO4)3 Coatings

3.4.1. Salt Spray Resistance Test

Salt spray resistance is a corrosion testing method with accurate and practical reference value [18]. The salt spray resistance test was conducted on the coating without and with Ba3Eu(PO4)3 (the molar ratio was 3:0.5:3), and the results are shown in Figure 7.
Compared with the anti-corrosion effects of different coatings in Figure 7, it can be observed that, after exposure to neutral salt spray for 24 h, the coating with 1 wt% Ba3Eu(PO4)3 addition showed significant whitening and foaming. After 48 h, the pure acrylic resin coating corroded extensively, and the coatings with 1 wt% and 2 wt% Ba3Eu(PO4)3 showed filamentous corrosion. The coatings with 3 wt% and 5 wt% Ba3Eu(PO4)3 showed spotted rust spots. But the coating with 3 wt% Ba3Eu(PO4)3 had more rust spots than the one with 5 wt%. After 72 h, the corrosion area of the pure acrylic resin coating increased and granular rust spots appeared. As the amount of Ba3Eu(PO4)3 addition increases, a stable passivation film can be formed on the substrate, providing isolation and protection. Therefore, Ba3Eu(PO4)3 can effectively prevent corrosion of acrylic resin. The coating added with 5 wt% Ba3Eu(PO4)3 exhibited the highest corrosion resistance.

3.4.2. SEM of Corrosion Coatings After Salt Spray Test

The microstructure of pure acrylic and coatings containing 5 wt% Ba3Eu(PO4)3 after salt spray testing for 72 h is shown in Figure 8.
As shown in Figure 8a–c, pure acrylic resin was composed of cross-linked “dendritic” particle macromolecules, with elongated corrosion scales accumulating on the surface in an arc-shaped manner, exhibiting phenomena such as bubbling and cracking. From Figure 8d–f, it can be seen that the surface roughness of the acrylic coating containing Ba3Eu(PO4)3 increased. The distribution of corrosion products was uniform and presented a clustered “petal-like” shape. It indicated that a dense passivation film was formed on the surface of the coating sample with 5 wt% Ba3Eu(PO4)3 added, which could effectively block the shuttle of corrosive media.

3.4.3. Electrochemical Test of Coatings

The Tafel curve is an important tool to reflect the kinetics of electrochemical reactions, providing a relationship between reaction rate and the concentration of reactants on the electrode surface. Electrochemical impedance spectroscopy (EIS) testing is a commonly used method for studying the corrosion resistance of coatings, which can intuitively reflect the corrosion behavior of coatings and help evaluate their long-term corrosion resistance [19]. By conducting immersion tests, impedance Bode plots, Nyquist plots, and phase plots were obtained to analyze and evaluate the anti-corrosion performance of the coating [20].
(1)
Tafel Curve
The samples were soaked in a 3.5 wt% NaCl solution and the Tafel curves of Ba3Eu(PO4)3 coatings tested for 24 h, 120 h, and 168 h were made. The results are shown in Figure 9, and the specific test data are shown in Table 2.
From Figure 9 and Table 2, it was revealed that rare-earth phosphate as filler added to acrylic resin significantly changed the corrosion current density and corrosion voltage of the coating. The corrosion voltages of pure resin coating and coating with 1 wt% Ba3Eu(PO4)3 were not significantly different at 24 h, 120 h, and 168 h. At 24 h, the minimum corrosion current of the coating with 3 wt% Ba3Eu(PO4)3 was 7.793 μA/cm2, followed by the coating with 5 wt% Ba3Eu(PO4)3, which had a corrosion current of 8.82 μA/cm2. However, the 3 wt% Ecorr (−0.676 V) was higher than 5 wt% Ecorr (−0.736 V). That means the addition of 3 wt% coating had a better corrosion inhibition effect in the early stage of corrosion. At 120 h and 168 h, the corrosion current of the coating with 5 wt% Ba3Eu(PO4)3 is lower, being 10.96 μA/cm2 and 9.616 μA/cm2, respectively. The lower the corrosion current, the stronger the corrosion resistance of the material. When the corrosion currents of materials are not significantly different, those with higher corrosion potentials exhibit better corrosion resistance. The corrosion current and voltage of the coating with Ba3Eu(PO4)3 added were both lower than those of the pure acrylic resin, indicating that Ba3Eu(PO4)3 significantly enhanced the corrosion resistance of water-based acrylic coatings.
(2)
Nyquist Curve
Coatings with different amounts of Ba3Eu(PO4)3 were immersed in 3.5 wt% NaCl aqueous solution for 24 h, 120 h, and 168 h, respectively. The experimental results were fitted and analyzed using an equivalent circuit model. Subsequently, the electrochemical parameters of the coating corrosion process were displayed as Nyquist plots, shown in Figure 10.
The arc radius of the Nyquist plot represents the impedance value. The larger the arc radius, the better the anti-corrosion performance of the coating [21]. From Figure 9, it can be seen that the capacitance arc diameter of the coating with added Ba3Eu(PO4)3 was always larger than that of pure acrylic coating. As the soaking time increased, the capacitance arc radius decreased, which may be due to the infiltration of corrosive media into the coating. The resistance R of the coating gradually decreased, leading to a decrease in anti-corrosion effect. However, the capacitance arc diameter of the 5 wt% Ba3Eu(PO4)3 coating was the largest.
(3)
Bode Curve
Figure 11 shows the Bode plots of coatings with different amounts of Ba3Eu(PO4)3 addition and immersed in 3.5 wt% NaCl solution for 24 h, 120 h, and 168 h.
In the Bode plot of impedance modulus values, the time constant in the mid- to high-frequency range represents the characteristics of the coating. Meanwhile, the impedance modulus values below the mid- to low-frequency range (f < 0.1 Hz) are frequency independent and mainly used to measure the protective performance of the coating. The larger the value, the better the protective effect of the coating [22]. The time constant in the low-frequency range represents the characteristics of metal interface corrosion under the coating. In the Bode phase angle curve, the higher the phase angle curve, the smaller the coating capacitance value, the larger the resistance value, and the less electrolyte infiltration into the coating/metal interface [23]. In addition, in the phase angle curve, a peak–valley pair represents a time constant, which can be used to determine the corrosion process of the coating system with the Nyquist plot [24].
From the Bode plots in Figure 11b,d,f, it can be seen that the coating system exhibited at least one time constant. Combined with the Nyquist plot, it was believed that the coating system had two time constants, namely, the impedance spectrum of the coating showed two capacitive arcs. Coatings with different Ba3Eu(PO4)3 addition amounts exhibited different amplitudes of capacitive arcs in the high-frequency range. Overall, the addition of 2 wt% and 5 wt% yielded better results. From the Bode plots in Figure 11a,c,e, the 3 wt% Ba3Eu(PO4)3 coating had the highest impedance in the low-frequency region after 24 h and 120 h of corrosion. However, the impedance value of the 5 wt% addition was significantly lower compared to the low-frequency region, while the impedance value of the 2–5 wt% additions was similar in the high-frequency region. This may be due to the saturation of the coating, resulting in a decrease in the anti-corrosion performance of the coating [25,26]. By 168 h, the Ba3Eu(PO4)3 coating containing 2 wt% and 5 wt% exhibited high impedance in both low- and high-frequency regions.

3.4.4. Equivalent Circuit

The equivalent circuit diagram and data according to the Nyquist curve are shown in Figure 12 and Table 3.
Rs, Rf, and Rct represent solution resistance, membrane resistance, and charge transfer resistance, respectively. CPEf, CPEdl, and Zw are thin film capacitors, double-layer capacitors, and Warburg diffusion coefficients, respectively [27].
The corrosion rate of metals decreases with the increase in Rct and Rp. In the later stage of corrosion, the electrolyte is closely related to the dielectric constant, and an increase in CPEf promotes the diffusion of the electrolyte [28]. The Rct value is positively correlated with the protective performance of the coating, while a decrease indicates a decrease in the resistance of the coating to the penetration of corrosive media [29].
From Table 3, it can be seen that the Rct values of Ba3Eu(PO4)3 coatings with addition amounts of 2 wt%, 3 wt%, and 5 wt% showed an overall upward trend, indicating that the Ba3Eu(PO4)3 deposited on the substrate surface can effectively suppress grain boundary corrosion after the corrosive medium enters the coating. Ba3Eu(PO4)3 slowly released Eu3+ ions and reacted with hydroxyl ions, which were generated in the cathode region to form a protective layer. Phosphates as corrosion inhibitors formed a dense protective film on the surface of the substrate, which can achieve a dual anti-corrosion effect. In summary, the type and amount of fillers are closely related to the anti-corrosion performance of the coating.

3.5. Anti-Corrosion Mechanism

The anti-corrosion mechanism of Ba3Eu(PO4)3 in the presence of an acrylic coating is shown in Figure 13.
There are usually four reasons for corrosion, namely, physical corrosion, chemical corrosion, electrochemical corrosion, and microbial corrosion. Due to the presence of micropores or defects on the surface of metal substrates, primary batteries are easily formed, where the anode region substrate loses electrons and becomes Fe2+ and the cathode region produces OH−. Therefore, this system is mainly characterized by electrochemical corrosion. The corrosion rate depends on the ion migration rate, ion concentration, and the difference in positive and negative electrode potentials.
With the penetration of corrosive media, the acrylic coating containing Ba3Eu(PO4)3 ionizes to form Ba2+, Eu3+, and PO43−, which first form Ba3(PO4)3 precipitate (ksp = 3.4 × 10−23), effectively reducing the ion concentration of the microcell. Eu3+ plasma has a larger radius, slower migration speed, and lower corrosion current. In an alkaline system, Eu3+ and Fe3+ were deposited and passivated, resulting in Eu(OH)3 and Fe(OH)3 precipitates [30] (ksp was 8.9 × 10−24 and 4.0 × 10−38, respectively), effectively reducing the potential difference between the positive and negative electrodes and slowing down the electrochemical corrosion rate. Secondly, the passivation film was dense and highly amorphous, which had a certain barrier effect on oxygen. Therefore, as the amount of Ba3Eu(PO4)3 addition increases, the thickness of the passivation film increased and the anti-corrosion effect became more excellent. According to Table 2, the increase in corrosion potential impedes the anodic reaction. Table 3 shows that, as the charge transfer resistance increases, the hindrance to charge transfer between the electrode and the corrosive solution also increases [31]. The results of the salt spray resistance test and electrochemical test in Figure 10 were consistent. The correctness of the anti-corrosion mechanism diagram of the acrylic coating with added Ba3Eu(PO4)3 was verified.

4. Conclusions

In this study, a novel Ba3Eu(PO4)3 as white powder and with a fluffy pore structure was prepared by a high-temperature solid-phase method. When the mole ratio of BaCO3:Eu2O3:(NH4)H2PO4 = 3:0.5:3 and it is ground for 30 min and calcined at 950 °C for 2000 min, the purest product was obtained. Compared with pure resin, the salt spray resistance test showed that the coating filled with Ba3Eu(PO4)3 had excellent barrier properties. When the addition amount of Ba3Eu(PO4)3 was 5 wt%, the anti-corrosion effect was the highest. The corrosion current was minimal at 9.616 μA/cm2. A mechanism model for adding Ba3Eu(PO4)3 anti-corrosion coating was established.

Author Contributions

X.D.: original draft preparation, visualization; J.W.: writing, review and editing, formal analysis; S.W.: funding acquisition; J.Z.: data curation, software; X.Z.: editing; Y.Z.: data curation, software; Z.D.: supervision. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Natural Science Foundation of Shanghai (23ZR1425700) and the Science and Technology Commission of Shanghai (20DZ2255900).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available in the article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Polymers 17 01966 g001
Figure 1. XRD patterns of Ba3Eu(PO4)3 with different ratios of BaCO3, Eu2O3, and (NH4)H2PO4.
Figure 1. XRD patterns of Ba3Eu(PO4)3 with different ratios of BaCO3, Eu2O3, and (NH4)H2PO4.
Polymers 17 01966 g001
Polymers 17 01966 g002
Figure 2. XRD patterns of Ba3Eu(PO4)3 generated within different reaction times.
Figure 2. XRD patterns of Ba3Eu(PO4)3 generated within different reaction times.
Polymers 17 01966 g002
Polymers 17 01966 g003
Figure 3. SEM spectrum and elemental mapping image of Ba3Eu(PO4)3.
Figure 3. SEM spectrum and elemental mapping image of Ba3Eu(PO4)3.
Polymers 17 01966 g003
Polymers 17 01966 g004
Figure 4. EDS image of Ba3Eu(PO4)3.
Figure 4. EDS image of Ba3Eu(PO4)3.
Polymers 17 01966 g004
Polymers 17 01966 g005
Figure 5. SEM image of Ba3Eu(PO4)3.
Figure 5. SEM image of Ba3Eu(PO4)3.
Polymers 17 01966 g005
Polymers 17 01966 g006
Figure 6. TEM image of Ba3Eu(PO4)3 at different magnifications: (a) 10 nm; (b) 5 nm.
Figure 6. TEM image of Ba3Eu(PO4)3 at different magnifications: (a) 10 nm; (b) 5 nm.
Polymers 17 01966 g006
Polymers 17 01966 g007
Figure 7. Salt spray resistance of coatings with different amounts of Ba3Eu(PO4)3.
Figure 7. Salt spray resistance of coatings with different amounts of Ba3Eu(PO4)3.
Polymers 17 01966 g007
Polymers 17 01966 g008
Figure 8. SEM of corrosion coatings after 72 h salt spray test: (a–c) pure acrylic resin coatings; (d–f) 5 wt% Ba3Eu(PO4)3 coatings.
Figure 8. SEM of corrosion coatings after 72 h salt spray test: (a–c) pure acrylic resin coatings; (d–f) 5 wt% Ba3Eu(PO4)3 coatings.
Polymers 17 01966 g008
Polymers 17 01966 g009
Figure 9. Tafel polarization curves of Ba3Eu(PO4)3 coatings with different added amounts over time.
Figure 9. Tafel polarization curves of Ba3Eu(PO4)3 coatings with different added amounts over time.
Polymers 17 01966 g009
Polymers 17 01966 g010
Figure 10. Nyquist plot of Ba3Eu(PO4)3 coating with different addition amounts over time.
Figure 10. Nyquist plot of Ba3Eu(PO4)3 coating with different addition amounts over time.
Polymers 17 01966 g010
Polymers 17 01966 g011
Figure 11. Bode plots of Ba3Eu(PO4)3 coating with different addition amounts over time.
Figure 11. Bode plots of Ba3Eu(PO4)3 coating with different addition amounts over time.
Polymers 17 01966 g011
Polymers 17 01966 g012
Figure 12. The Equivalent circuit of coatings.
Figure 12. The Equivalent circuit of coatings.
Polymers 17 01966 g012
Polymers 17 01966 g013
Figure 13. Schematic diagram of corrosion protection mechanism of Ba3Eu(PO4)3.
Figure 13. Schematic diagram of corrosion protection mechanism of Ba3Eu(PO4)3.
Polymers 17 01966 g013
Table 1. Formula of rare-earth barium phosphate coatings.
Table 1. Formula of rare-earth barium phosphate coatings.
Raw Materialwt/%
Waterborne acrylic lotion50.0–60.0
Defoamer C-150.4–0.6
Deionized water15.0–8.0
pH regulator DMAE0.2–0.4
Wetting agent G-0330.5–1.0
Leveling agent HTK-30200.5–0.8
Film-forming aid alcohol ester 122.4–3.0
Anti-flash-rust agent NaNO21.0–2.0
Thickener WT-105Aappropriate amount
Dispersant 50400.4–0.8
Ba3Eu(PO4)30–5.0
Total100
Table 2. Tafel test data of coatings with different Ba3Eu(PO4)3 additions.
Table 2. Tafel test data of coatings with different Ba3Eu(PO4)3 additions.
SamplesTime (h)Ecorr (V)Icorr (μA/cm2)Rp (Ω)ba−bc
0 wt%24−1.068135.903720.8177.785
120−1.127505.201071.3096.754
168−1.082495.701220.0767.104
1 wt%24−1.03680.624473.4418.617
120−1.02876.925671.4768.497
168−1.02670.6534193.1565.108
2 wt%24−1.01524.0312321.7368.866
120−0.88814.7029774.6525.285
168−0.78412.9234164.3575.493
3 wt%24−0.6767.79352024.3216.404
120−0.91615.3934193.1565.108
168−0.86813.3333004.6045.281
5 wt%24−0.7368.8245914.5046.232
120−0.79410.9637345.5215.107
168−0.8389.61650233.7145.288
Ecorr: corrosion potential, V; Icorr: corrosion current density, μA/cm2; Rp: polarization resistance; ba: the anode Tafel slope; bc: the cathode Tafel slope.
Table 3. The electrochemical impedance spectroscopy data of coatings with different Ba3Eu(PO4)3 additions.
Table 3. The electrochemical impedance spectroscopy data of coatings with different Ba3Eu(PO4)3 additions.
Time
(h)		Additive Amount (wt%)Rs (Ω·cm2)CPEf
(Ω−1·cm−2·s−n)		Rp
(Ω·cm 2)		CPEdl
(Ω−1·cm−2·s−n)		Rct (Ω·cm2)Zw
(Ω·cm2)
2406.277.18 × 10−6193.701.14 × 10−434990.002
14.965.05 × 10−622.311.1 × 10−438400.030
24.496.34 × 10−623.501.1 × 10−447660.002
33.794.95 × 10−622.071.2 × 10−436540.002
55.457.58 × 10−620.649.85 × 10−541120.030
12000.013.59 × 10−6341.302.46 × 10−71.58 × 1092.90 × 10−7
136.756.08 × 10−720581.38 × 10−85.37 × 1059.66 × 10−6
22.708.62 × 10−53.031.04 × 10−47.83 × 1061.31 × 10−3
32.511.08 × 10−43.428.41 × 10−631605.99 × 10−4
52.904.72 × 10−52.106.02 × 10−641541.05 × 10−3
168017.568.64 × 10−550123.50 × 10−35333.69 × 107
111.367.95 × 10−542.775.73 × 10−530714.77 × 10−4
2122.401.16 × 10−623,6008.42 × 10−81.79 × 1036.76 × 10−6
3183.801.70 × 10−731807.11 × 10−72.73 × 1031.63 × 10−6
591924.38 × 10−1165673.28 × 10−84.03 × 1073.81 × 10−8
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MDPI and ACS Style

Deng, X.; Wang, J.; Wen, S.; Zhao, J.; Zhang, X.; Zhao, Y.; Deng, Z. Preparation of Barium Europium Phosphate and Its Performance in Acrylic Resin Anti-Corrosion Coating. Polymers 2025, 17, 1966. https://doi.org/10.3390/polym17141966

AMA Style

Deng X, Wang J, Wen S, Zhao J, Zhang X, Zhao Y, Deng Z. Preparation of Barium Europium Phosphate and Its Performance in Acrylic Resin Anti-Corrosion Coating. Polymers. 2025; 17(14):1966. https://doi.org/10.3390/polym17141966

Chicago/Turabian Style

Deng, Xuying, Jihu Wang, Shaoguo Wen, Jiale Zhao, Xue Zhang, Yicheng Zhao, and Zhiying Deng. 2025. "Preparation of Barium Europium Phosphate and Its Performance in Acrylic Resin Anti-Corrosion Coating" Polymers 17, no. 14: 1966. https://doi.org/10.3390/polym17141966

APA Style

Deng, X., Wang, J., Wen, S., Zhao, J., Zhang, X., Zhao, Y., & Deng, Z. (2025). Preparation of Barium Europium Phosphate and Its Performance in Acrylic Resin Anti-Corrosion Coating. Polymers, 17(14), 1966. https://doi.org/10.3390/polym17141966

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