Tafel Polarization Tests Research Articles

Graphene composite coating for enhanced corrosion resistance of Ni foam flow field in PEMFC

With the development of proton exchange membrane fuel cells (PEMFCs), metal foam with lightweight advantages and highly porous structures has become promising flow field material to replace traditional carbon plates. However, in the operating environment with high temperatures and acid situation, it suffers severe corrosion issues. To solve this problem, Sn and Sn/graphene composite coatings are prepared and the physical characteristics are analyzed by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Tafel polarization test, potentiostat test, and electrochemical impedance spectroscopy are used to test the corrosion resistance of coated nickel foam in a PEMFC cathodic environment. Compared to Sn-coated foam, the corrosion resistance is further enhanced with the addition of graphene. The Sn/graphene coating obtained by electrodeposition at current density of 15mA·cm–2 has the lowest corrosion current density, which accounts for only 41.20% and 33.48% of the uncoated foam value at 50°C and 80°C, respectively. It also exhibits the maximum coating resistance, the lowest potentiostatic current and interfacial contact resistance, which is 66.3% lower than the US DOE 2025 goal. After an 8h constant potential test, no noticeable pitting behavior is shown on the surface because of the compact Sn/graphene coating. The addition of graphene promotes the nucleation of Sn metal and results in lower Sn oxidation.

Stepwise-Induced Synthesis and Excellent Corrosion Protection of Ce/Eu Codoped ZnO Solid Solution Materials.

Under purely inorganic conditions, a synthesis route was devised wherein elements were introduced stepwise via coprecipitation based on differences in compound solubility. This synthesis method can change the microscopic morphology of the material without relying on a templating agent, resulting in the formation of the multilayered lamellar Ce/Eu codoped zinc oxide solid solution (ZCEOSS) with a self-assembled nested imbrication structure. The study improves the critical matter of corrosion by focusing on the electron and energy transfer mechanisms. By introduction of the bandgap modulator cerium element and fluorescence enhancer europium element into the ZnO material, the anticorrosion material has been successfully endowed with both photocathodic protection and luminescent initiative/stress dual corrosion defense functions. Due to the energy level staircase protection mechanism synergistically generated by the 4f electron shell of rare-earth elements in concert with semiconductor zinc oxide, the energy band positions were modulated to progressively guide the direction of electron flow, thereby suppressing corrosion reactions. In particular, the ZCEOSS material synthesized by doping 1% cerium and 7% europium and adding rare-earth elements at pH 7 exhibited the best corrosion inhibition performance. After immersion in simulated seawater for 96 h, Tafel polarization test results showed that compared to epoxy resin and ZnO anticorrosion systems, the ZCEOSS anticorrosion system exhibited significantly improved corrosion inhibition efficiency with enhancements of 1028.3 and 402.9%, respectively. This study provides new insights into the development of highly efficient inorganic anticorrosion materials.

A new study on the effects of clay nanoparticles on the corrosion performance of Al-Si-Cu matrix composites in both acidic and alkaline solutions

In this paper, the influence of clay nanoparticles on the corrosion properties of the Al-Si-Cu matrix was investigated. The nanocomposite fabricating method was stir-casting when stirring times and temperatures were variables to change nanocomposite characteristics. Several corrosion tests were performed to examine the relationship between the microstructure and the degradation mechanism of various fabricated nanocomposites. Tafel polarization measurements indicated a lower corrosion rate for all nanocomposites compared to the Al-Si-Cu matrix in 0.1 M NaOH solution. The reduction range was 23.6–79.0% based on the smaller size of Si precipitates. In this situation, the interconnection of surface pores was lowest. However, electrochemical impedance spectroscopy (EIS) results showed that nanocomposite impedance would be increased up to 99.7% in comparison to the matrix without clay nanoparticles in 1 M HCl solution when the stirring temperature was 750 °C. EIS calculation also displayed that an increase (about 17.1–50.8%) in the nanocomposite resistance would be achieved when the stirring time was 2 min in 0.04 H2SO4 solution. The reason could be attributed to the larger size of Si particles since coarse precipitates were more effective agents to act as barriers for anodic dissolution of the lower layer of the Al-Si-Cu matrix when Tafel polarization tests demonstrated that the anodic reaction controlled the corrosion rate of the aluminum matrix.

Properties and corrosion protection of polypyrrole prepared by electrochemical polymerization on aluminum

AbstractIn a one‐step procedure that did not require any surface preparation, polypyrrole (PPy) films doped with 3‐nitrosalicylic acid (3Nisa) became effectively electropolymerized on the aluminum substrate in aqueous solutions. Fourier transform infrared, scanning electron microscopy, and thermal gravimetric analysis were used to analyze the properties of PPy‐based films. Open circuit potential (OCP), electrochemical impedance spectroscopy, Tafel polarization, and salt spray tests were used to study the corrosion‐resistant efficiency of the coatings. The as‐prepared PPy films performed corrosion resistance on aluminum in the 3% NaCl solution. However, the PPy films prepared in the 0.01 m solution of 3Nisa showed the best protection ability on aluminum. The self‐healing characteristic of the PPy films was recorded by varying the potential in the OCP measurement. The findings indicate the potential of using 3‐nitrosalicylic acid‐doped PPy films for applications as anti‐corrosion coatings for aluminum.

Towards an antibacterial self‐healing coating based on linseed oil/ZnO nanoparticles repair agent, encapsulated in polyurea formaldehyde microcapsules

AbstractThis research aims at investigating the idea of anti‐bacterial self‐healing coatings based on polyurea formaldehyde microcapsules (MCs), with the repair agent being ZnO‐containing linseed oil. ZnO nanoparticles were added to the repair agent with the idea of developing an antibacterial coating. The idea was to entrap some ZnO nanoparticles inside microcapsules, aiming for some local release of ZnO nanoparticles where the coating is damaged. The corrosion resistances of the coatings were studied using the Tafel polarization test. The structure of the coating samples was evaluated using a scanning electron microscope. To check the antibacterial properties of ZnO‐containing self‐healing samples, Escherichia coli and Staphylococcus aureus bacteria were used. Results showed that ZnO nanoparticles were distributed not only inside microcapsules but also over the walls, inferring that overall protection can also be attained in addition to local anti‐bacterial performance. Results showed that the proposed multi‐functional coating has promising antibacterial and self‐healing responses.

Evaluations of microstructure and electrochemical characteristics of Al-Si-Cu/clay nanocomposites in two corrosive solutions

Effects of manufacturing parameters on the electrochemical properties of aluminum-based nanocomposite with clay reinforcement have been investigated as a new study. Tafel polarization and electrochemical impedance spectroscopy tests at ambient temperature and in two corrosive environments were used to investigate the characteristics of the fabricated nanocomposites. Examination of different specimen microstructures was performed by optical and scanning electron microscopy before and after electrochemical tests. Electrochemical measurements indicated that nanocomposites had a higher corrosion rate in 0.6 M NaCl solution compared to the Al-Si-Cu matrix. The lower content of the Si and AlCu4 precipitates was a major parameter in reducing corrosion attacks. However, nanocomposites exhibited a higher corrosion resistance in comparison with the aluminum matrix in 0.02 M H3BO3 solution. Such an increase range was about 25.3–70.3 % concerning nanocomposites. The highest resistance was attributed to the nanocomposite stirred for 2 mins at 800 °C. In this situation, a higher content of Si precipitates (up to 30 %) with a small size was an effective factor in forming a passive layer at the matrix surface and acting as an obstacle for further corrosive ions diffusion toward the inner layer of the material.

2-mercaptobenzimidazole inhibits corrosion and prolongs the lifetime of an epoxy resin coating on a copper-62 alloy surface in a simulated marine environment at 40 °C

Epoxy coatings are widely used on metal surfaces in marine environments, but are subject to corrosion. How to improve the corrosion resistance of such materials has therefore become an important research topic. In this study, the corrosion inhibitor 2-mercaptobenzimidazole (MBI) was added to the organic coating of the epoxy resin on the surface of the copper-62 alloy to extend the service life of the coating in marine environments. The corrosion inhibition efficiency of MBI for the copper-62 alloy in simulated marine environments was investigated by means of immersion corrosion tests, Tafel polarization tests, and electrochemical impedance spectroscopy (EIS). The effects of MBI on the damage process and water transport of epoxy coatings were also studied by EIS. It has been shown that MBI acts as an adsorption corrosion inhibitor by electro-attractively adsorbing on the surface of a copper substrate. For a total mass fraction of 0.5 wt. %, the corrosion inhibition efficiency was more than 90%, and the corrosion current density of the copper-62 alloy in simulated seawater with MBI was 6.01 × 10−7 A cm−2. The corrosion current density of the copper-62 alloy in simulated seawater is 1.382 × 10−5 A cm−2. When MBI was added to the epoxy organic coating at a ratio of 0.5 wt. %, the diffusion coefficient of the coating was as low as 9.72 × 10−11 cm2 s−1, and the time to failure of the coating was extended to 1656h, compared to the epoxy coating without the corrosion inhibitor. It has been demonstrated that the addition of MBI can increase the service life of copper-62 alloy/epoxy coatings in marine environments effectively.

Eco-Friendly Electrodeposition of Al-Zn Alloy from AlCl3-Urea Deep Eutectic Solvent

The electrodeposition of Al-Zn alloy from an aluminium chloride-urea (AlCl3-urea) deep eutectic solvent (DES) containing 0.1 M ZnCl2 near room temperature was investigated. Cyclic voltammetry demonstrates that Al and Zn can be co-deposited, but the presence of Zn(II) restrains the reduction of Al(III). Linear sweep voltammetry reveals that increasing temperature facilitates the reduction of Zn(II) and Al(III), but the promotion effect on the Zn(II) reduction is greater than that on Al(III) reduction. Chronoamperometry analysis indicates that the electrocrystallization of Al-Zn alloy on a glassy carbon electrode follows instantaneous nucleation, which is similar to that of pure Al. SEM shows that the obtained alloy coating is smooth but not compact. With the increase of temperature, the content of Zn in deposits increases, the grain grows up and the microstructure transforms from granular to cluster structure. EDS and XRD analyzes prove that the deposits are pure Al-Zn alloy and composed of α phase and η phase. Tafel polarization test confirms the as-prepared alloy coating with higher Zn content (45 wt%) possesses excellent corrosion resistance. All these findings promise an eco-friendly and simple route to produce the Al-Zn alloy coating with excellent corrosion resistance near room temperature.

Investigation of corrosion behavior of Al–TiO2 nanocomposite produced using air plasma spray and accumulative roll bonding method

This work is an attempt to study the Al–TiO2 nanocomposite properties applying accumulative roll bonding process. For this purpose, nano Titania powder was first coated on aluminum foil by air plasma spraying process. The nanocomposite was then fabricated in one, two, three, five, and seven cycles by ARB. To investigate the effect of ARB process cycles on an Al-5% wt. TiO2 nanocomposite, characterization tests including XRD, quantitative XRD analysis by MAUD software, FESEM, EDS, electrochemical impedance, and TAFEL polarization tests were performed on the samples. The results indicate that the crystallite size reduced from 156 to 31 nm and the dislocation density quadrupled in the composite. The results of XRD analysis showed an increase in the dislocation density in the composite when the number of cycles increases. The reduction of crystallite size and increase of the grain boundaries have caused a sudden increase in the dislocation density. As the ARB cycle increases, the local porosity decreases and the local cracks due to the separation of the titanium sprayed droplets disappear in the matrix phase, and the reinforcing phase has more diffusion in the matrix. With the increase of ARB cycles, the percentage of titanium and oxygen elements on the surface was decreasing, but they remained until the last cycle. Among the non-rolled and rolled samples in different cycles, ARBed samples after 1 cycle and 5 cycles had not only the lowest and highest corrosion current densities but also the highest and lowest total resistance (Rt), respectively. This indicates max corrosion resistance due to the decrease in defect and porosity resulting from plasma spray and min corrosion resistance as a result of formation of galvanic cell between Al-matrix and Ti-reinforcing particles, respectively.

Water-soluble chitosan salt as ecofriendly corrosion inhibitor for N80 pipeline steel in artificial sea water: Experimental and theoretical approach

Chitosan, as a proficient biopolymer, has enormous potential as an ecofriendly corrosion inhibitor (CI), but their limited solubility restricts practical applications. Herein, an eco-friendly and water-soluble chitosan salt (CS) was utilized as a green CI on N80 pipeline steel in artificial sea water. Several structural and surface analytical tools were engaged in describing the characteristics of novel CS polymer. The corrosion inhibition efficiencies of CS on steel at different concentrations were investigated through gravimetric, conventional and advanced electrochemical techniques along with the surface analyses. Tafel polarization tests specified that CS performed as mixed-type CI with prevalent anodic inhibition characteristics. At a concentration of 1000 ppm, CS provided an inhibition efficiency (IE) of 96.68 %, following physiochemical adsorptions of CS on N80 surface validated by fitting Langmuir adsorption isotherm. However, the reductions in the values of IE at high temperature specified that the CS is the temperature dependent CIs. Scanning electrochemical microscopic evaluation confirmed the formation of thin CS inhibitors films with high electrochemical stability on N80 steel in saline. The performed surface characterizations on inhibited surfaces validated the adsorption of CS on the N80 surface by forming thin inhibitor film to obstruct metal corrosion. The theoretical simulation studies using molecular dynamics and density functional theory corroborated the experimentally obtained results.

Enhancement of corrosion resistance of CrMoV low alloy steels using cryogenic treatment

The current investigation explores the effect of cryogenic treatment on the microstructural and corrosion behavior of CrMoV low-alloy steels. The casted samples in the required dimensions were treated by annealing followed by deep cryogenic treatment (DCT). Initially, the microstructural modification brought by combined treatments was studied using an optical microscope (OM), scanning electron microscope (SEM), and x-ray diffraction (XRD) technique. After DCT, a refined and uniform grain structure was identified. The DCT resulted in the development of a fine-grained structure and reduced the mean grain size of the alloy, and this refinement of the grain structure is due to the reduction of lattice defects during the cooling process. The corrosion behavior was studied using the weight loss and Tafel polarization tests. The corrosion findings indicated a significant enhancement in the corrosion resistance of the specimens after DCT. The DCT specimens exhibited higher corrosion potentials compared to the base material. The DCT can promote the development of a more protective passive layer on the sample’s surface. This passive layer serves as an obstacle, preventing the diffusion of corrosive products and increasing corrosion resistance. Finally, it suggests that DCT positively impacts the CrMoV steels’ resistance to corrosion.

Design, synthesis, and evaluation of high‐performing anticorrosive polyurethane coatings with inbuilt redoxable oligomeric aniline segments

AbstractThis paper presents, a facile route for the synthesis of electroactive hybrid polyurethane‐urea's (EPUU) using back‐bone modification with diamine‐capped trianiline (DCTA) and diamine‐capped tetraaniline (DCTAni) oligomers. These EPUUs were loaded with different weight percentages (12.5, 25, and 50) of DCTA and DCTAni and named PU‐DCTA (12.5, 25, and 50) and PU‐DCTAni (12.5, 25, and 50), respectively. The formation of oligomers and their EPUUs were confirmed by using formal characterizations such as FTIR, HRMS, UV–Visible spectroscopies, and electrochemical studies. TGA, DSC, and tensile studies were conducted on the cured films to better understand the structure and property relations. The mechanical and thermal properties of EPUU films are as high as 60.0 MPa tensile strength and T5% at 322°C, and the adhesion strength of 300‐μm films on mild steel was observed as 533 psi. Tafel polarization and electrochemical impedance spectroscopy (EIS) measurements were used to determine these polymers' anti‐corrosive capabilities. An accelerated salt‐spray test that revealed the coatings are stable for up to 600 h when exposed to 5% NaCl fog. The high corrosion resistance observed for PU‐DCTAni was found to be 6.874 × 10−6 mm/year from the Tafel polarization test, and its high polarization resistance was found to be up to 55.912 MΩ.

Electrophoretic Deposition, Microstructure, and Selected Properties of Poly(lactic-co-glycolic) Acid-Based Antibacterial Coatings on Mg Substrate.

There is an urgent need to develop biodegradable implants that can degrade once they have fulfilled their function. Commercially pure magnesium (Mg) and its alloys have the potential to surpass traditional orthopedic implants due to their good biocompatibility and mechanical properties, and most critically, biodegradability. The present work focuses on the synthesis and characterization (microstructural, antibacterial, surface, and biological properties) of poly(lactic-co-glycolic) acid (PLGA)/henna (Lawsonia inermis)/Cu-doped mesoporous bioactive glass nanoparticles (Cu-MBGNs) composite coatings deposited via electrophoretic deposition (EPD) on Mg substrates. PLGA/henna/Cu-MBGNs composite coatings were robustly deposited on Mg substrates using EPD, and their adhesive strength, bioactivity, antibacterial activity, corrosion resistance, and biodegradability were thoroughly investigated. Scanning electron microscopy and Fourier transform infrared spectroscopy studies confirmed the uniformity of the coatings' morphology and the presence of functional groups that were attributable to PLGA, henna, and Cu-MBGNs, respectively. The composites exhibited good hydrophilicity with an average roughness of 2.6 μm, indicating desirable properties for bone forming cell attachment, proliferation, and growth. Crosshatch and bend tests confirmed that the adhesion of the coatings to Mg substrates and their deformability were adequate. Electrochemical Tafel polarization tests revealed that the composite coating adjusted the degradation rate of Mg substrate in a human physiological environment. Incorporating henna into PLGA/Cu-MBGNs composite coatings resulted in antibacterial activity against Escherichia coli and Staphylococcus aureus. The coatings stimulated the proliferation and growth of osteosarcoma MG-63 cells during the initial incubation period of 48 h (determined by the WST-8 assay).

Synthesis of electrodeposited Co–P–ZrO2–CeO2 nanocomposite coating: Effect of heat treatment on corrosion and mechanical properties

Electrodeposited cobalt coatings have been considered a suitable replacement for hard chromium coatings due to their promising properties. In this research, electrochemical methods through the direct current technique have been applied to synthesize a novel Co–P–ZrO2–CeO2 nanocomposite coating. The addition of different phosphorous contents as a determinant of the crystalline or amorphous structure was investigated using X-ray diffraction (XRD). The needle-like or cauliflower morphologies and related elemental compositions were surveyed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The XRD, microhardness, wear, and corrosion resistance tests were conducted on heat-treated samples. The results illustrate that heat treatment significantly increases the microhardness of the amorphous nanocomposite layer (up to 1323 HV0.1). Additionally, it causes the best wear behavior for the nanocrystalline Co–P–ZrO2–CeO2 (0.2), while leading to a lower wear resistance for the amorphous coatings (0.65). Furthermore, applying heat treatment diminishes the corrosion behavior of the coating. Tafel polarization and electrochemical impedance spectroscopy (EIS) tests reveal that the best corrosion resistance has been achieved for an amorphous nanocomposite coating 11929 Ω cm2. These findings demonstrate that this coating has desirable properties for industrial applications.

Microstructure, mechanical and electrochemical studies of dissimilar friction stir welded aluminium alloys

In the present investigation, the influence of tool rotational speed (900, 1100, 1300, and 1500 rpm) on microstructure, mechanical characteristics, and corrosion behavior of friction stir welding (FSW) of dissimilar Al5083–6061 alloys was studied. Optical and scanning electron microscopes were used to study the microstructural features. The grain size measured at the stir zone (SZ) decreased considerably in contrast with the base materials (BM) but increased with tool rotational speed. The mixing degrees of two materials at the SZ are enhanced by increasing rotational speeds. The mechanical properties, such as hardness and tensile properties, were studied using Vicker’s hardness tester and universal testing machine. The hardness of the weld joints is inferior to that of the base metal, and uniform hardness distribution and the highest average hardness in SZ were obtained at 1100 rpm. The higher strength and elongation of 202 MPa and 5.2%, respectively, were achieved at 1100 rpm, with joint efficiency of 65%, due to optimum heat input, and the lowest tensile strength and elongation of 156 MPa and 3.2%, respectively, were obtained at 1300 rpm with a joint efficiency of 50% due to excess heat input. It is curious to note that an increase in tensile elongation accompanies the enhancement of weld strength. The fracture occurred at the retreating side of the heat-affected zone as it is the weakest zone in the FSWed joint. Different corrosion tests, such as immersion, open circuit potential, and Tafel polarization tests, were carried out using an electrochemical workstation. The corrosion findings showed that the corrosion resistance of the samples increased after the welding, and the highest corrosion resistance was obtained at 1100 rpm.

Properties of sodium molybdate-based compound corrosion inhibitor for hot-dip galvanized steel in marine environment

Abstract Sodium molybdate (Na2MoO4) was selected as the corrosion inhibitor, compounded with benzimidazole, in order to prolong the service life of the hot-dip galvanized steel (HDGS) in the marine environment in this article. XRD, SEM/FESEM and EDS were used to characterize the micro-morphology and elemental composition of HDGS. Immersion corrosion test, Tafel polarization and EIS test were carried out to study the effect of compound inhibitor on the corrosion resistance of HDGS in the marine environment. The best proportion of compound inhibitor was added to the self-made waterborne polyurethane coating (WPUC), aiming to evaluate its influence on the coating performance in the marine environment by immersion corrosion test and EIS test. The results showed that Na2MoO4, as a passivation type corrosion inhibitor, bounded Zn at the active sites of HDGS coupons and created structural defects. Benzimidazole, as an adsorption type corrosion inhibitor, was attracted by electricity and adsorbed at the structural defects. Under the premise of 1 wt% total content, the optimal ratio of Na2MoO4 & benzimidazole was 9:1 and the corrosion inhibition efficiency was 99.62%. The corrosion current density of HDGS in the simulated seawater with compound inhibitor was 5.650 × 10−8 A/cm2, while that of HDGS in the simulated seawater without compound inhibitor was 1.483 × 10−5 A/cm2. The WPUC containing compound inhibitor had a small decrease in corrosion resistance due to defects created by doping at the beginning of immersion, then the compound inhibitor would play an active role in the corrosion process to make more than double the service life of WPUC.

Effect of Bacillus and Pseudomonas biofilms on the corrosion behavior of AISI 304 stainless steel

Abstract In this research work, the corrosion tendency of stainless steel 304 caused by the Pseudomonas aeruginosa ZK and Bacillus subtilis S1X bacterial strains is investigated. The topographical features of the biofilms achieved after 14 days of incubation at 37 °C were examined by means of scanning electron microscopy. Fourier transform infrared spectroscopic analysis of the extracellular polymeric substance was carried out to estimate the chemical composition of the biofilm. Electrochemical impedance spectroscopy and Tafel polarization test methods were applied to understand the in-situ corrosion tendency of the stainless steel 304 in the presence of P. aeruginosa ZK and B. subtilis S1X strains. Compared to the biofilm produced by the P. aeruginosa ZK, the extracellular polymeric substance in the B. subtilis S1X containing bacteria was found to be porous and non-uniform. The improved hydrophobicity and uniformity of the P. aeruginosa ZK containing biofilm retarded the corrosion of the underlying stainless steel 304 sample. Appreciably large resistance of the P. aeruginosa ZK biofilm (∼6.04 kΩ-cm2) and hindered charge transport (11.12 kΩ-cm2) were evident from the electrochemical impedance spectroscopy analysis. In support of these results, a large cathodic Tafel slope (0.2 V/decade) and low corrosion rate (1.69 μA cm−2) were corroborated by the inhibitive properties of the P. aeruginosa ZK containing biofilm. However, the localized corrosion of the substrate in the presence of B. subtilis S1X bacteria was caused by the porosity and non-homogeneity of the extracellular polymeric substance layer. The small charge transfer resistance, high dissolution rate and pitting of the surface under B. subtilis S1X biofilm were comparable to the corrosion properties of stainless steel 304 in a controlled medium. These results highlighted the poor corrosion inhibitive properties of the B. subtilis S1X biofilm compared to the P. aeruginosa ZK bacterial strain.

Polyoxometalate-modified ternary copper-tungsten-sulfide nanocrystals as high-performance counter electrode materials for quantum dots-sensitized solar cells

The Cu2WS4/[Me2NH2]11[CeIII(PW11O39)2] (CWS/CeIII(PW11)2) composite is synthesized by simple solvothermal method and first applied as a counter electrode material in CdS/CdSe/ZnS-sensitized quantum dot sensitized solar cell (QDSSCs). Due to the co-existence of copper and tungsten in different valence states, the ternary CWS has more redox active sites than the binary Cu2S. Besides, the conduction band of CeIII(PW11)2 and CWS are well matched, so the electrons transport from CB of CeIII(PW11)2 to CWS is a favorable exothermic process. Brunauer-Emmett-Teller (BET), electrochemical impedance spectroscopy (EIS), Tafel-polarization test (Tafel), open-circuit voltage decay (OCVD) and cyclic voltammetry (CV) tests all confirmed that 4% CeIII(PW11)2/CWS (CWS-4) has the highest electrocatalytic activity. Under simulated sunlight, QDSSCs with CWS-4 CE delivered a power conversion efficiency (PCE) of 6.63% (Jsc = 23.42 mA cm−2, Voc = 0.62 V, FF = 0.46), which is 12% and 44% higher than QDSSCs with CWS and Cu2S CEs, respectively. CeIII(PW11)2, as an "electron-transport mediator" to compound with CWS can generate "shallow electron traps", increase active sites, and effectively inhibit the recombination of charges, thereby enhancing cell performance.

Characterization of plants and seaweeds based corrosion inhibitors against microbially influenced corrosion in a cooling tower water environment

This study compares the inhibitory activities of methanolic extraction of various plants including Artemisia pallens (MEAP), mangrove leaves like Rhizophora mangle (MERM), Avicennia marina (MEAM) and seaweeds such as Pandia povanica (MEPP), Sargassum tenerrimum (MEST) on the corrosion of mild steel (MS) coupons that were incubated on Pseudomonas stutzeri (P. stutzeri) SKR4 strain isolated from the cooling tower water (CTW). The activities of inhibitors are found using GCMS analysis and interactions between microbes and inhibitors were examined in the test for antibacterial activity, minimal inhibition concentration, biofilm formation assay. These all show an excellent inhibitory effect against P. stutzeri. The weight loss, impedance spectroscopy, and Tafel polarization tests used to validate the corrosion investigations show that the inhibitors MEAP-75, MERM-71, MEAM-69, MEPP-66 and MEST-63 % are effective at inhibiting corrosion at 25 ppm. According to Potentiodynamic polarization plots, these five inhibitors act as mixed-type inhibitors. The surface investigation of MS metals by FTIR, SEM, XRD to examine the biofilm surface and it revealed deep pitting corrosion in the bacterial system. In the conclusion, eco-friendly green inhibitors have controlled the biocorrosion in cooling tower water and are recommended for usage in industries as an alternative to environmentally hazardous inhibitors.

Deposition of electroless Ni–Cu–P coatings on L80 steel substrates and the effects of coatings thickness and heat treatment on the corrosion resistance

In this study, the effect of adding colloidal copper nanoparticles to the electroless Ni–P bath on the corrosion behavior and microstructure of electroless coatings was investigated. Hence, the effects of coating thickness and heat treatment on the corrosion behavior of Ni–P and Ni–Cu–P coatings were studied. For this purpose, Ni–P and Ni-Cum-P electroless coatings with different thicknesses (0.1–75 μm) were deposited on L80 steel substrates. Moreover, the resulted coatings were heat treated at 200 and 400 °C. Microstructural examinations and X-ray diffraction patterns confirmed the alteration of cauliflower to orange peel morphology at high thicknesses by the addition of Cu nanoparticles to the electroless Ni–P bath. The results of Tafel polarization and electrochemical impedance spectroscopy tests in 3.5% NaCl solution indicated that for non-treated samples treatment, the corrosion resistance was improved by increasing the thickness of the coating due to the filling of the micropores. Furthermore, the corrosion resistance was highly increased for the sample treated at 400 °C for 1 h because of the increase in the Ni3.8Cu phase in the electroless Ni-Cum-P coating. In addition, it was observed that at thicknesses above 50 μm, the corrosion resistance of the samples treated at 400 °C was reduced due to the formation of microcracks. Nevertheless, the highest corrosion resistance was attributed to the electroless Ni-Cum-P coating with a thickness of 25 μm and the Ni–P coating with a thickness of 50 μm.