Corrosion Inhibition Efficiency Investigation of Yttrium Oxide Nanoparticles Coated on Carbon Steel Alloy

: Metal oxide nanoparticles demonstrate uniqueness in various technical applications due to their suitable physiochemical properties. In particular, yttrium oxide nanoparticle(Y 2 O 3 NPs) is familiar for technical applications because of its higher dielectric constant and thermal stability. It is widely used as a host material for a variety of rare-earth dopants, biological imaging, and photodynamic therapies. In this investigation, yttrium oxide nanoparticles (Y 2 O 3 NPs) was used as an ecofriendly corrosion inhibitor through the use of scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FT-IR), UV-Visible spectroscopy, X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy(EDX), the physico-chemical characterization of Y 2 O 3 NPs was examined. The primary characteristic peak of YOY at 565 cm -1 , which indicates the synthesis of nanoparticles, is seen in the FT-IR spectra. The XRD pattern showed that a single phase cubic structure of YONPs with an Ia-3 space group had formed. SEM was used to examine the surface morphology. The composition of Yttrium and oxygen in Y 2 O 3 NPs was determined to be 78.74% and 21.26%, respectively, according to the EDX results. The anticorrosive behavior was tested by polarization curve in 18.204% CaCl 2 solution at five temperatures in the range 293-313 K. Various concentrations 0.15 0.26 and 0.37 of N Y 2 O 3 NPs coating on the carbon steel surface were applied using the electrophoresis deposition method. The obtained results indicated that Y 2 O 3 NPs formed a protective film acts as a physical barrier for the protection of steel alloy. Additionally, corrosion protection efficiency values of 0.26 N Y 2 O 3 NPs coating were superior to that of 0.15 and 0.37 N Y 2 O 3 NPs coating, respectively.


Introduction:
The majority of economies in the world rely heavily on the transportation and distribution of resources, including oil, gas, chemicals, water, steam, and petroleum products. They play a significant role in our infrastructure. Electrochemical degradation, sometimes known as corrosion, poses a serious danger to the integrity of these important assets 1 . An electrochemical reaction in an aqueous medium, often soil water or portions of the goods they carry, results in the corrosion of pipelines. The process of electron transfer is a crucial part of corrosion. Most corrosion integrity management solutions include monitoring and mitigation systems that keep an eye on the voltages and currents connected to the corrosion process 2,3 . Recent studies have shown that nano coating materials are essential for increasing corrosion resistance in challenging environments, improving mechanical qualities, and minimizing dimension changes. In addition to corrosion resistance, mechanical characteristics, making it smoother, stronger, and improving its adhesive qualities are just a few of the numerous advantages that may be realized thanks to nano coating's exceptional capabilities 4 . One kind of valuable rare earth element called yttrium oxide (Y2O3), an inorganic nanoparticle, has appealing antibacterial and antioxidant properties 5 . Numerous studies claim that Y2O3 has greater levels of hardness and is chemically stable [6][7][8] . The corrosion resistance and toxicity of yttrium oxide are both high 9 . Recapitulated are the chemical processes used to create nanoparticles, including sol-gel, emulsion, solid-state reactions, combustion, colloid reaction techniques, and hydrothermal processing 5 . However, these procedures are expensive, harmful to the environment, and fraught with biological dangers 10 . Due to the availability of several natural resources, inexpensive, and non-toxic ingredients, the production of nanoparticles from plant extracts has considerably increased 11 . Renal carcinoma cells have been effectively inhibited by greenly produced Y2O3NPs. The synthesis process is an affordable, environmentally sustainable, and alternative to physical and chemical procedures with less negative side effects 12 . Green synthesis of yttrium oxide (Y2O3) nanoparticles using lantana camara leaf extracts have been studied 13 .
These nanoparticles were characterized with the aid of different methods, including UV, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), transmitted electron microscopy (TEM), and photocatalytic degradation. Y2O3 nanoparticles showed an excellent antibacterial activity against Gram-positive Bacillus subtilis and Gram-negative Escherichia coli with a 10 to 15 mm inhibitory zone. Green Y2O3NPs were released with a 4 hours lag time and 80% sustained release rate, indicating that they could be used in drug delivery. In addition, the bioavailability of green Y2O3 NPs was investigated using cell viability in cervical cancer cell lines. A low-cost electrochemical method called electrophoretic deposition (EPD) that can be used at room temperature and deposit several components simultaneously in a single coating phase has made it possible to create multifunctional coatings [14][15][16][17] . In addition, EPD may be used to coat complex-shaped samples since it can be applied to any solid in the form of powders that can be dispersed in a solvent to create stable suspensions 18,19 . The fabrication of micro-and nanostructured ceramics using this method is possible for a variety of uses, including biological, optical, and corrosion protection 20 .
In the present study, yttrium oxide nanoparticles were used. The structure, morphology and formation of YONPs were characterized by various techniques including FT-IR, UV-Visible, XRD and SEM-EDX analysis. The electrochemical studies were carried out in CaCl2 solution using various temperatures and concentrations of YONPs coating on mild steel surface through electrophoresis deposition technique. kinetic and thermodynamic parameters of the coated and uncoated sample were also measured.

Materials
Carbon steel alloy was used to build the water application pipes in Iraq. The carbon steel used in this research has the following weight percentage composition: P (0.018), Mo (0.03), Ni (0.017), C (0.19), Si (0.35), Cr (0.04), Cu (0.02), Al (0.06), and the rest was iron as revealed by emission spectroscopic analysis. Chemicals of analytical reagent grade were used to prepare the solutions. Working electrodes were formed in the shape of cylindrical objects and had a surface area of 1 cm 2 . The sample was polished to a mirror finish using emery paper of various grades 320, 500, 1000, 2400, and 4000, a diamond product spray, aqueous ethanol and diamond particles of various sizes 1, 3, 6, and 9 mm, and lastly, distilled water as a final rinse.

Solutions Preparation
Dissolving 182.04 g of CaCl2 in 1000 mL of distilled water yielded an 18.204% calcium chloride solution. Yttrium oxide nanoparticles (Sigma-Aldrich) (99.9% purity) coating solution, in various concentrations 0.15, 0.26, 0.37 N, was prepared by dissolving 0.3, 0.5, and 0.7 grams of Y2O3NPs in 50 ml of acetyl acetone, adding a small amount of iodine to the solution to increase its conductivity.

Electrophoresis Deposition
The yttrium oxide nanoparticles were electrophoretically deposited (EPD) onto a carbon steel substrate utilizing a direct current (DC) power supply with a voltage range of 0 to 15 V. The circuit is employed by the AC meter to measure the current created between the electrodes, and a 50 ml covered beaker contains two slits with a distance of 1 cm between them. Meanwhile, a stainless steel tong is used to catch the carbon steel specimen as well as the carbon steel rod that serves as the inert electrode in the deposition process cell. The deposition of specimens takes place over a period of 5 to 30 minutes, after which the sample is left at room temperature for 24 hours to dry gradually. A thick film was applied to carbon steel surface after the EPD technique described above to ensure a homogeneous coating.

Electrochemical Studies
To perform electrochemical measurement, this is done by using electrochemical System Potentiostat/Galvanostat (M Lab (WENKING MLab multichannel and SCI-MLab system for corrosion measurement obtained from Bank Electronics-Intelligent controls GmbH, Germany 2007) , the M-Lab works on a desktop computer (Windows XP). To perform corrosion measurements, the device is attached to a corrosion cell made up of three electrodes: a carbon steel alloy for the working electrode, a platinum electrode for auxiliary purposes, and a saturated Calomel electrode (SCE) for reference purposes. Eq. 1, is used to calculate the percentage of inhibition efficiency (%IE) of yttrium oxide against corrosion of a carbon steel sample in calcium chloride solution 21 .
corr corrosion current density for blank and icorr corrosion current density of a carbon steel coated with different concentrations of nano-yttrium oxide at the same temperature.

Polarization Measurements
The polarization curves for corrosion of carbon steel in 18.204 % CaCl2 solution for blank and various concentrations of Y2O3 NP coatings at different temperatures 293, 298,303,308 and 313 K are illustrated in Fig.1 (a, b, c and d).
Electrochemical parameters as corrosion current density (icorr), corrosion potential(Ecorr), cathodic (bc), and anodic (ba) Tafel slopes are given in Table. 1.  The data obtained listed in Table. 1, indicates the following :-1-Coating the carbon steel alloy with yttrium oxide nanoparticles and with concentration mentioned in Table 1 indicates the diffraction of the voltage in the direction of an increase in negative values from the equilibrium potential, which means that the protection we obtained is cathodic protection 22 .

2-
It has been observed that the rate of corrosion increased with increasing the temperature because temperature accelerates corrosion process such as electrochemical reaction, chemical reaction, and the process of transferring of reactive species to the metal surface 23 .

3-
At the concentrations of 0.15 and 0.26 N, it was found that increasing the concentration with growing temperature increases the efficiency of inhibition, as it was noticed that the activation energy increase ( Table 2) from 30.25 kJ/ mol at 0.15N to 51.55 kJ/ mol at 0.26, which is an evidence of the occurrence of chemical adsorption between the Y2O3NPs and the metal surface 24 .

4-
At the concentration 0.37N, an increase in the corrosion rate and decrease in the inhibition efficiency was observed due to occurrence of agglomeration in the Y2O3 NPs deposited on the metal surface 24 . Activation energy data (Table 2) increases with increasing concentration which is an evidence of the occurrence of physical adsorption that is the bonding of Y2O3NPs through Van der Waals forces with the metal surface 25 .

Thermodynamics Parameters
Thermodynamic parameters of the corrosion reaction includes activation energy Ea ,entopy ∆S* and enthalpy ∆H* of activation were calculated using Arrhenius Eq. 3 26  Where CR: corrosion rate, Ea: the apparent activation energy, R: universal gas constant 8.314 J mol -1 K -1 , T : temperature, A: the Arrhenius pre-exponential factor, h : Plank's constant 6.626176 x 10 -34 J.s., N : Avogadro's number 6.022 x 10 23 mol -1 , ΔS * is the entropy of activation and ΔH * is the enthalpy of activation. The log corrosion rate is plotted against 1/T for the blank and Y2O3NPs coated carbon steel in CaCl2 solution as shown in Fig.2. The log CR/T is plotted against 1/T for the blank and Y2O3NPs coated carbon steel in CaCl2 solution and ΔH * , ΔS * values were obtained, respectively from the slop and intercept as presented in Fig.3. Data obtained is tabulated in Table. 2.   From Fig. 2, it is observed that the relationship between corrosion rate and temperature is linear , and the corrosion rate decrease when the concentration of the inhibitor is 0.15N and 0.26N , but the corrosion rate increased at 0.37N to be close to the corrosion rate of blank , as mentioned previously due to agglomeration in yttrium oxide nanoparticles, the nature of the bonding of molecules to the metal surface is physical adsorption 23,27 . The negative values of ΔS* reveal that the activated complex in the rate determining step represents association rather than the dissociation step, this means a decrease in disorder take place 28 .

4.Characterization
The Y2O3 nanoparticles were characterized by UV-Visible, FTIR, XRD, SEM, and AFM techniques. Y2O3 nanoparticles were optically measured using a UV-visible absorbance spectrophotometer. The UVvisible spectrum of the examined nanoparticles was recorded in the range (200-800 nm) using a Varian, Cary 5000 with a scanning rate of (600nm/min). Y2O3 nanoparticles were optically measured using a UV-visible absorbance spectrophotometer at room temperature. The advent of Y2O3's yttrium adsorption in the UV band at 284.0 nanometres is a sign of the nano scale 28 . The absorption spectrum of nano yttrium oxide is shown in Fig.4. FT-IR spectroscopy was used to analyse yttrium oxide nanoparticles; the spectrum was recorded in the range 400-4000 cm -1 . The FT-IR spectrum of Y2O3 is shown in Fig.5 where a sharp peak that appeared at 565 cm -1 is an evidence of absorption Y-O stretching vibration, the peak at 588 cm -1 corresponds to the anti-symmetric Y-O-Y stretching. The peak at 873 cm -1 is responsible for the presence of trace of Y-OH. The peaks at 1216, 1085 and 1026 cm -1 are the characteristic asymmetric stretching of Y-O-Y present in the nanostructure 29 . The appearance of the result in Fig. 5 is closed to 29 above where we find the appearance of its absorption by functional groups: At 560.61 cm -1 : Y-O (sharp peak) stretching vibration 676.02 cm -1 : O-Y-O anti symmetric stretching 848.49 cm -1 :Y-OH trace amount 1510.9-1404.3 cm -1 asymmetric stretching.

Figure 5. FT-IR spectrum of Y2O3 nanoparticles.
To further investigate the structural properties of nano -Y2O3, we used XRD technique. Fig. 6 shows the XRD pattern of Y2O3 nanoparticles. The result obtained from XRD indicated that the Y2O3 has single phase cubic structure with Ia-3 space group. In addition, there were no any peaks in any phase or impurities in the XRD graph . SEM -(SIGMA HV -Carl Zeiss with Bruker Quantax 200 -Z10 EDS Detector) were used to measure the surface morphology (The shape and size of the particles). Fig. 7 shows SEM image of pure Y2O3 nanoparticles. It was noticed that the surface of the Y2O3 NPs is uniform and homogeneous with the observation of a little agglomeration of nanoparticles, but it takes a regular geometric shapes. To determine the chemical composition of nanoparticles, an EDX analysis was obtained. Fig. 8 shows the EDX spectrum of Y2O3 NPs, where only Y and O are shown; this indicates that the material is pure and does not contain impurities. AFM is an effective method for statically assessing the distribution of particle sizes as well as investigating surface shape at the nano to micro scale. Fig. 9 shows an AFM image of pure yttrium oxide nanoparticles where the particle diameter, surface roughness, surface waves and three dimensional shape are shown. The lower the roughness values, the more corrosion resistance 30 . In the AFM result below, the surface roughness is very low which is evidence that the nanomaterials have a high corrosion resistance. We note from the result that agglomeration of particle occurs and the highest agglomeration occurs at 45 nm diameter for the agglomerated particles.

Conclusions:
Y2O3NPs were successfully deposited on a carbon steel alloy surface by using an electrophoretic deposition technique. The layer deposited of these nanoparticles on the metal surface was characterized using various techniques, such as UV-visible, FT-IR, X-ray diffraction, SEM, and AFM. XRD data revealed that Y2O3NPs were pure single-phase cubic structures. The AFM result indicates that the surface roughness is very low, which is evidence that the nanomaterials have high corrosion resistance. We note from the result that agglomeration of particles occurs and the highest agglomeration occurs at 45 nm in diameter for the agglomerated particles. SEM image of pure Y2O3 nanoparticles indicates that the surface of the Y2O3 NPs is uniform and homogeneous with the observation of a little agglomeration of nanoparticles, but it takes a regular geometric shape. The percentage of corrosion inhibition of Y2O3NPs was found to be high, especially at a nanoparticle concentration of 0.26 N as observed from corrosion rate data, which is lower than the other concentrations. Additionally, increasing the temperature decreases the inhibition efficiency at all concentrations and it was found that increasing the concentration of the inhibitor above 0.26 N increases the corrosion rate due to the agglomeration of the nanomaterial on the alloy surface. Thermodynamic studies reveal that the nature of the bonding of molecules to the metal surface is physical adsorption. The negative values of ΔS* reveal that the activated complex in the rate determining step represents association rather than dissociation. This means a decrease in disorder takes place.