Low Carbon Steel Substrate Research Articles

Characterization of Ni-Cu multilayers deposition on low carbon steel substrate using electroplating technique

Abstract Low carbon steel is widely used in oil and gas applications. In this research, multilayers of Nickel (Ni) and Copper (Cu) were deposited on a low carbon steel substrate using the electroplating process (ELP). Initially, a layer of Ni was coated, followed by a layer of Cu. ELP was implemented using water bath containing (300 g/l) of NiSO4.6H2O, (30 g/l) of (NiCl2.6H2O), (40 g/l) of H3BO3 and (30 g/l) of (NaCN), (30 g/l) of (CuCN), (10 g/l) of (NaOH.6H2O). First bath parameters were temperature is (59 - 60 °C), current density in the range of (3-5 A/dcm2), voltage was holed at (8 V) for Ni, and temperature was between (50-51 °C), current density in the range of (1-2 A/dcm2), voltage was holed at (4 V), while the plating time (10 minutes) for both Ni and Cu. The results refer to Ni, Cu, and Ni & Cu ELP thicknesses 3, 4.77 and 6.75 μm respectively. Metallurgical tests were achieve including the micro hardness of ELP, Vickers micro hardness results showed improvement in hardness values compared, with steel substrate, and in the presence of Ni, Cu, Ni+Cu layers, 322, 581, 479, and 562 Hv respectively. The roughness was measured using surface roughness measurement device. The average surface roughness (Ra) depicted satisfying values as a result of Ni layer coating, which gave uniform surface distribution with Ra 0.363 μm. X-ray diffraction (XRD) test examinations serve as strong evidence for the presence of Ni and Cu in the internal and external finish layers, respectively. Corrosion examinations were carried out in seawater solution (3.5 g NaCl) the corrosion behavior tends to be more resistance, with layers of Ni, and Cu in sea water environment, which is considered an important criterion to increase the part life.

Characterization and electrodeposition mechanism of Ni–Mo coatings from self-regulating electrolyte

Electrochemical Ni–Mo coatings were obtained on a low-carbon steel substrate using a stable, environmentally safe, self-regulating electrolyte containing 0.2 M NiCl2, 0.3 M Na3C6H5O7, and SrMoO4 (saturated). The effects of electrolyte pH, temperature, deposition current density, and hydrodynamic conditions on chemical composition and morphology of the coatings were studied. It was established that the addition of ammonia to the electrolyte contributes to the deposition of a more uniform, globular, nonporous coatings morphology. The effect of ammonia on the formation mechanism of coatings was substantiated. The stages of deposition and the limiting stage of the formation of Ni–Mo coatings from citrate-ammonia electrolytes, which involves the chemical reduction of molybdenum oxide (IV) to molybdenum, were determined using cyclic voltammetry.

Особенности тонкой структуры Ni-Al покрытий, полученных методом HV-APS

Introduction. Development of Ni-Al intermetallic compounds is one of the priority directions of modern machine building. Due to such characteristics as high heat resistance, high temperature strength, and low density, nickel aluminides are used as functional coatings in the aerospace industry. The main methods of Ni-Al coating surfacing are High-Velocity Oxygen-Fuel and High-Velocity Air-Fuel spraying (HVOF and HVAF), atmospheric plasma spraying (APS) and its modification such as High-Velocity Atmospheric Plasma spraying (HV-APS) which provides non-equilibrium cooling conditions. Since there are eight different intermetallic compounds, as well as martensite transformation, Ni-Al coatings is quite interesting to study. The work purpose is to study the features of the martensitic structure in HV-APS coatings, and also to establish the effect of heating temperature on its decomposition. Materials and methods. Ni-Al coatings were surfaced onto a low-carbon steel substrate using the HV-APS method. Studies of the fine structure of the coatings were carried out using transmission electron microscopy (TEM). In addition, the influence heating temperature on structural transformations of the coatings was analyzed. Results and discussion. Two types of particles are formed in HV-APS coatings: with a dendritic and granular structure. The most part of HV-APS coatings consists of particles with a two-phase grain structure (NiхAl1-х and γ'-Ni3Al grains). Only NiхAl1-x grains undergo martensitic transformation at cooling. Martensite in large grains (sizes greater than 500 nm) has a lamellar structure, while small grains are completely transformed into one martensite plate. In addition, the coatings contain grains in which martensite plates (NiхAl1-х) and β-phases alternated. It is shown the behavior of martensitic plates at colliding with each other, as well as with the γ′-Ni3Al grain. Heating up to 400 °C contribute the begins of martensite decomposition in individual grains with the release of a secondary phase; after heating up to 600 °C all martensite dissolves.

A study integrating in-process thermal signatures, microstructure, and corrosion behaviour of AISI 316L coatings on low carbon steel substrate deposited by laser-directed energy deposition (L-DED)

Surface coating through Laser Directed Energy Deposition (L-DED) of AISI 316L on low-carbon steel was carried out by varying laser fluence. The resulting melt pool characteristics, obtained through IR pyrometer, played a significant role in evolution of the microstructure. A higher heat input resulted in an equiaxed grain structure with finer grain sizes and improved deposition quality. The quantitative phase analysis revealed the presence of a dominant austenite phase and a secondary ferrite phase, along with traces of molybdenum carbide. Corrosion analysis reveals improved resistance at a higher laser fluence, attributed to increased content of corrosion-resistant alloying elements (Mo, Cr) and predominance of the austenite phase. Electrochemical Impedance Spectroscopy (EIS) confirms a higher corrosion resistance at a higher laser fluence, supported by a significantly higher polarization resistance and presence of a duplex-structured passive film. Results indicate that moderate laser fluence levels, ranging from 5 to 7.5 kJ/cm2, accompanied by medium to high thermal signatures and moderate cooling rates, yield coatings with refined microstructures, enhanced mechanical strength, and corrosion resistance. For superior corrosion resistance, a laser fluence of 10 kJ/cm2 is recommended, although careful consideration of its potential impact on mechanical properties is advised.

Microstructure and Corrosion Study on Friction Surfaced Aluminum Alloy Coatings over Mild Steel

In this study, the low-carbon steel (AISI 1018 mild steel) substrate is coated with the aluminum alloys AA6082-T6, Al-20Zn, and Al-2Si-15SiC to improve its corrosion resistance by the friction surfacing (FS) technique. To produce a high-quality coating, friction surfacing process variables including spin speed, speed of travel, and the rate of feed are crucial. This experiment examines twelve friction-surfaced plates with different parameter combinations. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) examinations were carried out in order to comprehend the microstructure and chemical composition of the coating deposits and the area in contact between the coated surface and the substrate. Microstructure investigation reveals that the intermetallic combination of Fe-Al at the coating interface region is an effect of the elemental diffusion of Fe to aluminum at the contact interface. Then a uniform and fine-grained coating deposit is observed as a result of the continuous recrystallization of the consumable rod under frictional stress and heat generation. According to the outcomes of the microhardness test, the coated surface is roughly 15–16% harder than the consumable rod. The coating bond strength was measured using a ram tensile test, and it ranged from 102 MPa to 135 MPa. Finally, evaluation of corrosion behavior through immersion testing and pitting corrosion testing reveals that the coatings made of Al-20Zn and Al-2Si-15SiC exhibit good corrosive resistance in an alkaline environment.

Wear and corrosion resistance of Al2O3 and TiC deposition on steel substrate using self- propagating high temperature synthesis method

In the present work, a low-carbon steel substrate was coated with Al2O3 and TiC using self-propagating high temperature synthesis. The synthesized coatings were annealed at 450 °C for 2–6 h. The characteristics of the substrate, coated, and annealed samples were examined, including microhardness, wear resistance, and corrosion resistance. A pin-on-disc tribometer was employed to conduct the wear test by varying the load, sliding velocity, and distance. The impact of these factors on the wear rate and worn surface morphology was then examined. Further, corrosion resistance was evaluated using electrochemical corrosion testing with 3.5 wt% NaCl as electrolyte. Results showed that Al2O3 and TiC specimens annealed at 450 °C for 5 h and 4 h improved the microhardness by 1.3 and 1.06 times than that of as-coated specimens respectively. The synthesized Al2O3 and TiC coatings showed an abrasive wear mechanism at higher loads and tribolayer formation was observed at higher sliding velocity and distances. The corrosion and wear resistances of the samples were found as follows: substrate< Al2O3 coated < TiC coated < Al2O3 annealed < TiC annealed. The Al2O3 and TiC ceramic coatings were found to improve wear and corrosion resistance having potential applications in cement, petrochemical, and marine industries.

In-situ determination of micro-hardness in laser cladding of stellite using optical emission spectroscopy

Offline measurements in Laser Cladding (LC) processes, such as micro-hardness measurement, are destructive and time-consuming tests. Therefore, in-situ monitoring of clads parameters is of significant importance. In this study, we investigate the plasma plume emission produced during the LC process of Stellite 6 powder on a low-carbon steel substrate and its correlation with the micro-hardness of the clads over a wide range of LC parameters. It is demonstrated that a strong correlation between the spectral features in the UV region of 280–320 nm and micro-hardness exists, so that, the micro-hardness of samples can be determined by the total intensity of light in this range, within an average tolerance of 10 %. An exponential relation between hardness and UV radiation is empirically obtained that works very well for a wide range of dilutions, from 20 % to 70 %. It means that the UV spectra even determine the micro-hardness of samples with dilutions above 60 %, where the process shifts towards laser powder welding. This radiation is suggested to originate from the collisions of electrons with nano-sized clusters, which are produced during the laser interaction with the melt pool. The produced nanoparticles are the source of UV radiation and scatters the driving laser light, at the same time, processes that qualitatively explain the exponential relationship between the hardness and the UV light intensity.

Influence of Duty Cycle on the Phosphorus Content and Hardness of the Ni-P Coatings Produced by Pulse-Current Electroplating

Ni-P coatings were prepared on low carbon steel substrates using the pulse electrodeposition method. The influence of the pulse duty cycle on the phosphorus content and hardness of the Ni-P coatings was investigated. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) were employed to examine the surface morphology and chemical composition of the Ni-P coating layers. The results showed that an increased pulse duty cycle (20% - 80%) led to a decreased phosphorus content from 17.81 wt.% to 13.71 wt.%. The microhardness values were found to have an inverse relationship with the phosphorus content. The highest hardness of 538.22 ± 12.92 HV0.1 was obtained from the sample produced with a duty cycle of 80%, which had the lowest P content of 13.71 wt.%.

Effect of heating temperature on the behavior of reinforced zinc-rich coating with nanoparticles

An experimental study has been conducted to develop unique zinc-rich coatings for the protection of low carbon steel reinforcements. These coatings are applied to low carbon steel substrates and subjected to various temperatures (100 °C, 150 °C, 200 °C, and 250 °C) to assess their mechanical integrity, corrosion resistance, and durability, replicating extreme service environments. The study integrates different nanoparticle concentrations into the zinc matrix (including Zn only, 50% Zn + 50% TiO2, 50% Zn + 30% WC + 20% TiO2, 40% Zn + 40% Ni-Cr Alloy + 20% TiO2, 70% Zn + 30% WC, and 50% Zn + 50% Ni-Cr Alloy) to assess their reinforcement effectiveness and contribution to thermal stability. The performance properties are assessed using adhesion tests, coating ratings, hardness assessments, electrochemical analysis, and field emission scanning electron microscopy (FESEM). The findings reveal that zinc coatings with a composition of 50% Zn, 30% WC, and 20% TiO2 provide excellent adhesion, particularly beneficial for high-temperature applications. Coatings containing Ni-Cr alloy display outstanding thermal stability, a vital characteristic for withstanding high-temperature conditions. At 250 °C, evaluating the compositions for the most favorable potential at the highest current densities is imperative. Microstructural analysis from room temperature to 250 °C shows a significant improvement in the integration and refinement of WC and Ni-Cr within the Zn matrix, resulting in the coatings’ optimal performance.

Optimization of process parameters for laser cladding Stellite6 cobalt-based alloy

As a new remanufacturing technology, laser cladding can repair damaged parts in large valves in nuclear power plants. The objective is to enhance the surface morphology quality of parts post-remodeling, the paper optimizes the key process parameters in the laser cladding process. Numerical simulation was used to analyze the influence of each process parameter ( laser power, scanning speed, powder feeding speed) on the morphology of the cladding layer. The laser power and powder feeding rate were positively correlated with the width of the cladding layer, and the scanning speed was negatively correlated with the width of the cladding layer. The orthogonal experiments are designed based on the Taguchi method, and the Stellite6 single cobalt-based alloy cladding layer was prepared on the WCB low-carbon steel substrate. Analysis of variance and RSM was used to analyze the experimental results. The influence order of process parameters on the morphology of the cladding layer was determined. The regression prediction model was established to analyze the relationship between the process parameters and the morphology quality (width and height) of the cladding layer. The errors of the model are 5% and 3.5%, respectively. The optimal combination of process parameters is determined as follows: P = 1700 W, Vs = 8 mm/s, Vf = 26 g/min. The cladding layer prepared by the optimal process parameters has fine structure and good bonding. The accuracy of the predictions was validated using this model, which offered valuable theoretical guidance for predicting and controlling the geometric characteristics of the laser cladding of Stellite6 alloy.

The Importance of Current Density in Electrolytic Phosphate Coatings

Phosphate coatings have been a popular choice for the treatment of steels and other ferrous alloys for a number of decades. In the most common embodiment of the process, phosphate coatings are produced by a conversion reaction between the steel surface and an acidic conversion bath. The resulting coatings are composed of phosphate crystals which act as a physical barrier between the environment and the underlying metal, protecting it from corrosion and wear [1]. Despite being a cheap and well-affirmed technology, conversion phosphating has recently been scrutinized due to its high environmental impact. In fact, one of the main byproducts of the process is a sludge containing phosphates and heavy metals from the deposition bath.A potential solution to the environmental burden carried by the conversion process is represented by the electrolytic deposition method. In this case, the increase in interfacial pH necessary for phosphate precipitation is obtained by applying a cathodic polarization to the samples to coat in an electrolytic setup. As a consequence of the potential shift, substrate dissolution is prevented and so is sludge formation [2].In this work, we demonstrate how the choice of current density influences the resulting properties of zinc phosphate coatings obtained by electrolytic deposition on low carbon steel substrates. Aside from the deposition rate, the applied current density is found to be a determinant factor in the morphology of the coatings as it can be seen in Figure 1. In turn, this affects other properties such as wear and corrosion resistance.[1] B. Díaz, L. Freire, M. Mojío, and X. R. Nóvoa, “Optimization of conversion coatings based on zinc phosphate on high strength steels, with enhanced barrier properties,” J. Electroanal. Chem., vol. 737, pp. 174–183, Jan. 2015.[2] S. Jegannathan, T. S. N. Sankara Narayanan, K. Ravichandran, and S. Rajeswari, “Performance of zinc phosphate coatings obtained by cathodic electrochemical treatment in accelerated corrosion tests,” Electrochim. Acta, vol. 51, no. 2, pp. 247–256, Oct. 2005. Figure 1

High Entropy Alloy Deposition from an Aqueous Bath

A new alloy design approach based on the concept of high entropy alloy (HEA) has attracted attention during the last few years. HEA is defined as an alloy composed of five or more principal elements with a concentration between 5 and 35 at% of each element. Depending on the combinations of the elements, HEA could show high resistance to corrosion, fatigue and fracture toughness besides unique electrical and magnetic responses. The outstanding characteristic of HEA is attributed to the high mixing entropies and the severe lattice distortion related to the addition of multiple components. Due to this unique combination of properties and the potential for designing a wide variety of new materials, interests have been directed toward high entropy alloy films and coatings for applications where corrosion and oxidation protection are strongly required. This study attempted to deposit five elements (Ni-Co–Cu–Mo-W) from an aqueous bath on a low-carbon steel substrate by the direct current. The goal was to combine the properties of Ni-Co-Cu with Ni-W and Ni-Mo coatings. In this case, a HEA coating can be produced, which might maintain corrosion and wear resistance even at high temperatures and be suitable for application in aggressive environments. To understand better the role of entropy on the coatings properties, three electroplating systems were designed, including electroplating of five elements (Ni-Co-Cu-Mo-W), which was compared with electroplating of four elements (Ni-Co-Cu-W) and (Ni-Co-Mo-W). In this case, systems with different configuration entropy can be produced, and by characterizing them, the relationship between the entropy and the properties of the coating might be cleared.Electrodeposition was carried out in Hull-cell to find the alloy deposition's proper working window. The role of different parameters such as pH, current density, and complex agent on the coating's composition was studied. The morphology and composition of the Hull-cell coatings were checked by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy along with X-ray fluorescence spectroscopy. Finally, the hardness and corrosion resistance of the coatings was studied by the nanoindentation technique and polarization in NaCl. This study developed a single aqueous bath for the electrodeposition of Ni-Co-Cu-Mo-W, Ni-Co-Cu-W and No-Co-Mo-W, and suitable deposition conditions were determined. It was shown that besides the metal concentration ratio, pH was the most influential parameter in the codeposition of elements with different deposition mechanisms. Ni and Co were the main inducing elements in the deposition of Mo and W than Cu. In addition, Ni, Co, Mo and W deposited uniformly, while Cu showed a different behavior. A competition between Mo and W deposition was seen, and Mo deposited more preferentially than W. The coatings showed weak passivity behavior and comparison between coating’s corrosion resistance was a challenge since their corrosion behavior does not only depend on coating composition but also on coatings compactness and integrity. By comparing the nano-hardness of the coatings, it was seen that the Ni-Co-Cu-W system with even the lowest configurational entropy has the highest hardness value. Keywords: Electrodeposition; High entropy alloy; Alloy deposition; hardness; Corrosion resistance

Process monitoring by deep neural networks in directed energy deposition: CNN-based detection, segmentation, and statistical analysis of melt pools

The complex interaction between laser and material in Laser Wire Direct Energy Deposition (LW-DED) Additive Manufacturing (AM) benefits from process monitoring methods to ensure process stability and final part quality. Understanding the relationship between process parameters and melt pool geometrical characteristics can be used to effectively monitor and in-process control the process, as the melt pool geometrical characteristics serve as crucial indicators of process stability and quality.This study presents a novel in-situ monitoring approach for LW-DED, utilizing process images for melt pool segmentation, melt pool geometrical characteristics estimation, process stability assessment, and bead geometry prediction. The segmentation of melt pool objects was successfully accomplished using Convolutional Neural Networks (CNN)-based models, enabling the prediction of essential parameters such as melt pool area, height, width, center of area, and the center point of the bounding box enclosing the melt pool. Multiple models were compared regarding the accuracy and processing speed using a controlled central composite design and random experiments. We used an Inconel alloy 625 wire and two distinct substrate materials for deposition, a coaxial laser welding head with a 3 kW fiber laser, and an off-axis welding camera for monitoring.Among the CNN architectures evaluated, YOLOv8l demonstrated superior accuracy with mean Average Precision (mAP) values of 0.925 and 0.853 for Stainless Steel (SS) and low carbon steel (S355) substrates, respectively. Additionally, YOLOv8s exhibited a notable processing speed of over 114 frames per second, which indicates its suitability for real-time process control. Furthermore, the results indicate a significant correlation between process parameters and melt pool geometry variables. Notably, a clear correlation was established between melt pool characteristics and bead geometries obtained through microscopic examinations, including penetration depth and heat-affected zone. The analysis revealed a significant correlation for the bead area and width parameters. In relation to the bead height, while the correlation exhibited a lower magnitude compared to bead area and width, it remained responsive. In addition, the tensor masks derived from the developed models have proven to be highly effective in accurately predicting bead geometries.The results demonstrate the effectiveness of YOLO-based algorithms for detecting and segmenting the melt pool. Statistical analysis confirms the significance of stabilized process data and the accuracy of melt pool geometric models. We demonstrate that integrating advanced monitoring and control techniques using artificial intelligence methods like CNN can facilitate process stability and quality control.

Development of SiC Ceramic Reinforced Composite Interlayer Cladding with AISI304 Stainless Steel Wire on Low Carbon Steel Substrate Using TIG Cladding Process

Development of SiC Ceramic Reinforced Composite Interlayer Cladding with AISI304 Stainless Steel Wire on Low Carbon Steel Substrate Using TIG Cladding Process

Effect of current density on the texture, residual stress, microhardness and corrosion resistance of electrodeposited chromium coating

Textures and residual stresses are generated during electrodeposition of chromium coatings, which directly affect the performance of the coating. In this work, the variations of texture, hydrogen content, residual stress, microhardness and corrosion resistance of chromium deposited from hexavalent [Cr(VI)] chromium bath using direct current deposited technique were investigated. Electrodeposition experiments were carried out on the low carbon steel substrate by varying the key variable current density. The macrotexture of the coatings was studied by XRD. The crystal orientation and dislocation density were analyzed by EBSD. Residual stress was measured by the indentation method. The research demonstrated that a single preferred orientation on the (222) plane was found at current densities of 20 A/dm2, 35 A/dm2 and 50 A/dm2. At 40 A/dm2, a mixed preferred orientation on the (222) + (211) planes was discovered. Furthermore, the formation of the chromium coating texture was affected by the variation of hydrogen content, for higher hydrogen promoting grain growth along the (222) crystal plane. Notably, the microstructure-property relationship was developed. At the single preferred orientation of (222) plane, the corrosion resistance was more favorable. At the mixed preferred orientation of (222) + (211) planes, the coating surface achieved higher microhardness, but formed higher residual stress and more microcracks. Moreover, the better electroplating parameter was proposed. At 35 A/dm2, the coating had the fewer microcracks and the better overall performance. The higher microhardness of 753 HV was found. The more favorable corrosion resistance was discovered, with the breakdown potential and passive current density of 804.7 mV and 2.220 × 10−6 A/dm2. The lower residual stress of 61 MPa was found, which was about 81 % lower than the maximum stress. It was significant in industry for the enhancement of the service life of substrate and the optimization of the chromium coating process.

Correction to: Electrocatalytic activity of electrodeposited CoOx thin film on low-carbon unalloyed steel substrate toward electrochemical oxygen evolution reaction (OER)

Correction to: Electrocatalytic activity of electrodeposited CoOx thin film on low-carbon unalloyed steel substrate toward electrochemical oxygen evolution reaction (OER)

Development of hard and wear-resistant SiC-AISI304 stainless steel clad layer on low carbon steel by GMAW process

In the present investigation, a successful attempt has been done to utilize conventional gas metal arc welding (GMAW) setup to develop SiC reinforced AISI 304 stainless steel (ASS) clad layer on low carbon steel (LCS) substrate. The characteristics of the clad bead like bead profile and dilution depend on the GMAW processing parameters like GMAW voltage and consumable wire feed rate (CWFR). The clad deposition at a higher voltage range (30 V) developed a defect-free, uniformly distributed fine SiC-reinforced clad layer with better clad dilution with the substrate. Further, the SiC-reinforced clad layer showed a uniform distribution of fine SiC particles in the steel matrix and also the formation of different hard intermetallics like CrSi2, Mn3Ni2Si, Fe2C, Fe5C2, and Cr7C3 in the clad layer. The SiC-reinforced clad surface showed a significant improvement in Microhardness (up to 504 HV0.5) compared to the steel substrate (180 HV0.5). The clad layer also improved the adhesive wear resistance (upto 8.7 times) and abrasive wear resistance (upto 1.7 times) of low carbon steel substrate.

Novel Ni-P-Tribaloy Composite Protective Coating.

Oil and gas pipelines are subject to various forms of damage and degradation during their operation. Electroless Nickel (Ni-P) coatings are widely employed as protective coatings due to their ease of application and unique properties, including high wear and corrosion resistance. However, they are not ideal for protecting pipelines due to their brittleness and low toughness. Composite coatings of higher toughness can be developed through the co-deposition of second-phase particles into the Ni-P matrix. Tribaloy (CoMoCrSi) alloy possesses excellent mechanical and tribological properties making it a potential candidate for a high-toughness composite coating. In this study, Ni-P-Tribaloy composite coating consisting of 15.7 vol.% Tribaloy was successfully deposited on low-carbon steel substrates. Both the monolithic and the composite coatings were studied to evaluate the effect of the addition of Tribaloy particles. The micro-hardness of the composite coating was measured to be 6.00 GPa, 12% greater than that of the monolithic coating. Hertzian-type indentation testing was carried out to investigate the coating's fracture toughness and toughening mechanisms. The 15.7 vol.% Tribaloy coating exhibited remarkably less severe cracking and higher toughness. The following toughening mechanisms were observed: micro-cracking, crack bridging, crack arrest, and crack deflection. The addition of the Tribaloy particles was also estimated to quadruple the fracture toughness. Scratch testing was performed to evaluate the sliding wear resistance under a constant load and a varying number of passes. The Ni-P-Tribaloy coating exhibited more ductile behavior and higher toughness, as the dominant wear mechanism was identified as material removal, as opposed to brittle fracture in the Ni-P coating.

Study on diffusion kinetics of chromium and nickel electrochemical co-deposition in a NaCl–KCl–NaF–Cr2O3–NiO molten salt

Abstract The process of preparing surface composite by molten salt co-deposition is the result of the mass transfer of active particles in molten salt, electrochemical reduction, and solid diffusion. In this study, we prepared Cr–Ni alloy/low-carbon steel surface composites in NaCl, KCl, NaF, Cr2O3, and NiO melt salt system successfully, and analyzed the entire diffusion dynamics process, aiming to find out the limiting links and provide ideas for further improving the preparation efficiency. The results show that chromium and nickel ions are simultaneously reduced on the cathode surface through two and one steps, respectively. And an alloy layer with Fe content of 64.52 wt%, Ni content of 28.96 wt%, and Cr content of 6.52 wt% is formed on the surface of low-carbon steel substrate. The average diffusion coefficients of chromium and nickel atoms in the surface composites are 1.16 × 10−14 and 1.44 × 10−14 m2·s−1. The mass transfer process in molten salt is the limiting link in the whole preparation process.

Hybrid Zinc Coatings with Chitosan/Alginate Encapsulated CuO-Nanoparticles for Anticorrosion and Antifouling Protection of Mild Steel

The construction of anticorrosion coatings containing antifouling agents is an effective way to ensure the long-term durability of marine steel infrastructures. In this work, an innovative hybrid coating was prepared by introducing biocide CuO nanoparticles in ordinary zinc coating to improve its protective ability for steel in aggressive salt water environments. The CuO nanoparticles were embedded inside the matrix of chitosan/alginate complexes to prevent spontaneous copper leaching during corrosive attacks. Two procedures were applied for the electrodeposition of hybrid/composite zinc-based coatings on low-carbon steel substrates (DC current): first—the co-electrodeposition of encapsulated CuO nanoparticles with zinc on a cathode (steel) electrode from a sulfate electrolyte with a relatively low pH value of about 4.5–5.0 and second—the encapsulated CuO nanoparticles were electrodeposited from aqueous solution as an intermediate layer between two zinc deposits. The particles size and stability of suspensions were evaluated using dynamic light scattering. Both hybrid coatings were compared in terms of surface morphology and hydrophilicity (SEM and AFM analysis, contact angle measurement) and corrosion resistance (potentiodynamic polarization curves, polarization resistance). The protective characteristics of the coatings were compared in a 3.5% NaCl solution and artificial sea water. The hybrid coating showed 2–4 times higher polarization resistance than the bare zinc coating during a 30 day immersion in artificial sea water, indicating that this coating has the necessary characteristics to be used in a marine environment.