Optimized Electroless Ni-Cu-P Coatings for Corrosion Protection of Steel Rebars from Pitting Attack of Chlorides

The electroless plating method is the most convenient for the metallisation of dielectrics. During this statistical study of the process, complex relationships were found between the composition of the electrolyte and the deposition regime. The complexity of this technology is an important multifactorial object of the study. An adequate linear regression model for electroless deposition of Cu-Ni-P alloy coatings was obtained by conducting a planned factorial experiment. It allows predicting the thickness of the electroless deposited alloy coating based on certain values of the input parameters (concentrations of copper sulphate, nickel sulphate and sodium hypophosphite) in the studied factor space, as well as further optimisation of the process.

The table of L9 (34) of orthogonal design was adopted in the experiment. The optimal formulation and process conditions of electroless nickel plating on high strength aluminum alloy were determined. The influences of bath composition and operating conditions on the hardness and deposition rate were analyzed and discussed. The experimental results show that the optimal plating formulation were obtained, which were consisted of nickel sulfate hexahydrate(25g/L), sodium hypophosphite(20g/L) and sodium acetate(15g/L). The operating conditions are as follows: 80~85°C, pH value 5.0. The coating structure is more homogenous and compact, and the coating has good brightness. Meanwhile, the hardness is up to 376.8HV, and the deposition rate is 17.2μm/h. The order of effects on hardness is pH value, sodium acetate, sodium hypophosphite and nickel sulfate concentration in turn. The hardness of coating decreased after heat treatment on low temperature. When the temperature exceed 200°C, the hardness increased with temperature rising and reached the peak value at 400°C(565.3HV).

Electrical conductivity is an important property of electroless nickel plated fabric. The optimized electroless nickel plating method can provide useful information for textile industries to obtain optimum surface resistance and stable plating. In this study, a screening experiment with factorial design and response surface method (RSM) with central composite design (CCD) was used to optimize the electroless nickel plating on polyester fabric. A two-level full factorial design (FFD) was used to determine the effects of five factors, i.e. the concentrations of nickel sulfate, sodium hypophosphite and sodium citrate, pH and temperature of the plating solution on surface resistance of the electroless nickel plated fabric. It is found that the nickel sulfate concentration and temperature of the plating solution are the most significant variables affecting the surface resistance of electroless nickel plated fabric. The optimum operating condition is finally obtained by using a desirability function. The test for reliability for predicting response surface equations shows that these equations give an excellent fitting to the observed values. In addition, the deposit composition, surface morphology, crystal structure and electromagnetic interference (EMI) shielding effectiveness (SE) were studied. The EMI SE of the nickel plated polyester fabric obtained under the optimal condition is about 60 dB at the frequency ranging from 2 to 18 GHz.

This study focuses on the electroless deposition of Ni–P alloy over a copper substrate to minimize the corrosion rate of the substrate. Central Composite Design (CCD) has been performed using Design-Expert software for minimizing the corrosion rate of the coating. Along with that, CCD is also utilized to analyze the influence of various process parameters viz. concentration of Nickel Sulphate, the concentration of Sodium Hypophosphite and bath temperature. Potentiodynamic test has been employed to evaluate the corrosion rate of each of the coated substrates. In order to minimize the corrosion rate, optimization has been performed using particle swarm optimization (PSO). 21.59[Formula: see text]g/L of Nickel Sulphate, 26. 72[Formula: see text]g/L of Sodium Hypophosphite and 93.41°C as the bath temperature were the optimum conditions for the deposition of coating in order to achieve a corrosion rate value of 0.862[Formula: see text]mm/Yas obtained from the model analysis results. Further, Analysis of Variance (ANOVA) was implemented which corroborated that the parameter Nickel Sulphate along with the interaction between Sodium Hypophosphite and bath temperature were the significant ones in determining the corrosion rate of the coating deposited in optimized condition. Optical Microscopy, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray analysis (EDX) were conducted to study the surface morphology and the elemental composition of the coated substrate respectively.

The present work deals with the synthesis of chemically deposited nickel–phosphorous (Ni–P) coating on copper substrate. The process parameters are optimized for maximum hardness based on L[Formula: see text] Taguchi orthogonal design with three process parameters, viz., bath temperature, concentration of nickel Sulphate (a nickel source) and concentration of sodium hypophosphite (a reducing agent), respectively. This is considered and fitted into an L[Formula: see text] orthogonal array (OA) to find out the optimized condition for improved hardness of the coating. The optimized results were obtained from 35[Formula: see text]g/L of Nickel Sulphate, 20[Formula: see text]g/L of Sodium Hypophosphite and 90∘C of temperature. Analysis of variance (ANOVA) was performed to determine the significance of the individual process parameters. ANOVA showed that the factor Nickel Sulphate, the interaction between Sodium Hypophosphite and Temperature were significant in determining the hardness of the coating deposited in the optimized condition. The surface morphology, compositional and phase structure analysis of optimized sample are conducted with the help of scanning electron microscope (SEM), energy-dispersive X-ray analysis and X-ray diffraction (XRD) analyzer, respectively.

This research article considers optimization of the four process parameters based on corrosion and wear of electroless Ni-P-Cu coatings. The major characteristics indexes for performance selected to evaluate the processes are corrosion potential (E corr), corrosion current density (I corr) and wear. Among the corresponding four process parameters the first three are coating parameters, viz. concentration of nickel sulphate, concentration of sodium hypophosphite, concentration of copper sulphate and the fourth one is post deposition heat treatment temperature. The corrosion property, i.e. E corr and I corr, has been studied by potentiodynamic polarization test and the wear is measured in terms of wear depth by DUCOM TR-25 multi-tribotester with block on roller arrangement. In this study, the process is intrinsically combined with multiple performance indexes so that grey relational analysis is specially adopted to determine the optimal combination of coating parameters. Moreover, the weighted principal component analysis (WPCA) is applied to evaluate the weighting values corresponding to various performance characteristics so that their relative importance can be properly and objectively described. From the analysis the optimum combination of parameters for corrosion property and the optimum combination of parameters for corrosion and wear together are obtained. The chemical composition, surface morphology and phase behaviour are investigated using energy dispersive X-ray analysis, scanning electron microscopy and X-ray diffraction analysis, respectively.

Parametric optimization of electroless Ni-P-CNT coating using genetic algorithm to maximize the rate of deposition

: Electroless nickel (EN) plating is used to apply a protective coating to a substrate without the use of an electric current. Following a catalytic activation step, a nickel phosphorous alloy (NiP) is deposited through chemical reactions on the surface of the part. The advantages over other metal coatings include: (1) coating uniformity, (2) corrosion resistance, (3) wear resistance, (4) desirable magnetic and electrical properties, and (5) indifference to part shape. The most common nickel source is nickel sulfate. Nickel ions are reduced to nickel metal by accepting electrons from an electron donor, typically hypophosphite, present in solution as sodium hypophosphite. Some of the hypophosphite is reduced to phosphorous, and is co-deposited with nickel to form a NiP alloy. As the nickel is plated onto the part, the concentrations of nickel and hypophosphite in the bath decrease. Nickel sulfate and sodium hypophosphite are periodically added to replenish these losses. When 100 percent of the original nickel has been replaced, this is termed a metal turnover (MTO).

Electroless nickel-copper-phosphorus alloy platings from ammonia alkaline citrate bath (A-C bath) and caustic alkaline citrate bath (C-C bath) containing sodium hypophosphite as a reducing agent were investigated to determine the effect of copper ion concentration on the deposition rate, corrosion resistance and structure of the deposits. The basic bath composition was found to be: nickel sulfate +copper sulfate 0.1M, sodium hypophosphite 0.2M, sodium citrate 0.2M, pH10 (adjusted with NH4OH or NaOH); bath temperature was 80±2°C. The copper content in the nickel-copper deposits were found to be 0% to 44.5% in A-C bath and 0% to 69.0% in C-C bath, respectively, depending on the copper ion ratio in the plating bath. In A-C bath, the deposition rate increased considerably with the copper ion concentration in the bath, but in C-C bath, this effect was very small. The corrosion resistance of the deposits, containing 16.5% copper and 4.7% phosphorus, from A-C bath, and of the deposits containing 8.0% phosphorus, from C-C bath was excellent for a 0.5M sulfuric acid solution at 30°C.

Parametric optimization and minimization of corrosion rate of electroless Ni–P coating using Box-Behnken design and Artificial Neural Network

The effects of bath compositions and brighteners on corrosion resistance of bright nickel plating were studied. The results obtained were as follows:(1) The interaction between the concentrations of nickel sulfate and nickel chloride had no effects on corrosion resistance.(2) The interaction between the cathodic current density and the concentration of total nickel had effects on corrosion resistance. Higher corrosion resistance was obtained under the conditions of lower concentration of total nickel and lower cathodic current density, or the higher concentration of total nickel and the higher cathodic current density.(3) Corrosion resistance was varied according to the kind and concentration of brighteners in double nickel plating.(4) The interaction between the kind of brighteners and cathodic current density had effects on corrosion resistance.(5) However, in CASS test of triple nickel plating, the kind of brighteners and cathodic current density had no effects on corrosion resistance.

In this work, the electroless plating Ni-Cu-P on aluminium is obtained successfully by direct Ni-Cu-P plating method. The effect of bath compositions on the electroless plating rate and the properties of the electroless Ni-Cu-P deposits was studied by orthogonal test. The corrosion resistance, hardness, surface morphology and components of the coating were studied by using electrochemical workstation, digital micro-hardness SEM and EDS. The optimum bath formula obtained is 0.6g/L copper sulfate, 30g/L nickel sulfate, 35g/L sodium citrate, 25 g/L sodium hypophosphite, 20g/L acetic anhydride and right amount of self-made additive. The deposition rate, hardness and corrosion resistance are all good. The adhesion between the deposits and the matrix is better. The deposits is smooth and uniformity, smooth by SEM. The deposit contains Ni 78.90%, Cu 8.65%, P 12.46% by the analyses of energy disperse X-ray.

Electroless nickel plating bath containing glycine and sodium citrate as chelating agent by means of deposition rate, bath life and phosphorous content in the deposited films was studied and simultaneous analysis of ions in plating bath by isotachophoresis was tried. Bath composition was; NiSO4⋅6H2O 30g/L, NaH2PO2⋅H2O 30g/L, NH2CH2COOH 40g/L, Na3C6H5O7⋅2H2O 20g/L, Pb(NO3)2 2mg/L. Plating area was 400cm2; bath volume was 4L; and bath temperature 88±2°C. The supply solution was NiSO4⋅6 H2O 450g/L, NaH2PO2⋅H2O 500g/L, Pb(NO3)2 60mg/L. The deposition rate from this bath was 0.2-0.3μm/min, 2-3 times faster than the general malic acid bath. Bath life was more than 50 hours in continuous plating and about 6 turns could be obtained. Though phosphorous content in the deposited films depended on bath pH and the amount of sodiun hypophosphite, phosphorous content could be kept to 5-13wt% or 12wt% constant by adjustng the concentrations of nickel sulfate and sodium hypophosphite in the supply solution. Bath composition was so changed with plating that analysis of ions in the plating solution by isotachophoresis using 0.01mol HCl leading solution and 0.01mol sodium caproate terminal solution was tried. As a result of it, concentrations of hypophosphite, phosphite, phosphate ions and also of citric acid ion could be analysed simultaneously and with high precision.

Plants are subjected to various biotic and abiotic stresses that significantly impact their growth and productivity. To achieve balanced crop growth and yield, including for leafy vegetables, the continuous application of micronutrient is crucial. This study investigates the effects of different concentrations of copper sulphate (0, 75, 125, and 175 ppm) on the morphological and biochemical features of Spinacia oleracea and Avena sativa. Morphological parameters such as plant height, leaf area, root length, and fresh and dry weights were optimized at a concentration of 75 ppm copper sulfate. At this concentration, chlorophyll a & b levels increased significantly in Spinacia oleracea (462.9 and 249.8 \U0001d707\U0001d454/\U0001d454), and Avena sativa (404.7 and 437.63\U0001d707\U0001d454/\U0001d454). However, carotenoid content and sugar levels in Spinacia oleracea were negatively affected, while sugar content in Avena sativa increased at 125 ppm (941.6 µg/ml). Protein content increased in Spinacia oleracea (75 ppm, 180.3 µg/ml) but decreased in Avena sativa. Phenol content peaked in both plants at 75 ppm (362.2 and 244.5 µg/ml). Higher concentrations (175 ppm) of copper sulfate reduced plant productivity and health. Plants exposed to control and optimal concentrations (75 and 125 ppm) of copper sulpate exhibited the best health and growth compared to those subjected to higher concentrations. Maximum plant height, leaf area, root length, fresh and dry weights were observed at lower concentrations (75 and 125 ppm) of copper sulfate, while higher concentrations caused toxicity. Optimal copper sulfate levels enhanced chlorophyll a, chlorophyll b, total chlorophyll, protein, and phenol contents but inhibited sugar and carotenoid contents in both Spinacia oleracea and Avena sativa. Overall, increased copper sulfate treatment adversely affected the growth parameters and biochemical profiles of these plants.

Polyetheretherketone (PEEK) and its fiber-reinforced materials are thermoplastic polymer materials with broad application prospects. Depositing Ni-P alloy on them can improve their poor conductivity and electromagnetic shielding performance, and further expand their application field. The application effect of the plated parts is significantly impacted by the bonding strength between PEEK and coating. The bonding strength between non-metallic substrate and coating is largely influenced by the surface characteristics of the substrate. Therefore, it is significant to study how the surface roughness of PEEK materials and the modified fibers in materials affect the adhesion of the coating. In this study, Ni-P alloy was electroless deposited on PEEK, 30% carbon-fiber-reinforced PEEK (CF30/PEEK), and 30% glass-fiber-reinforced PEEK (GF30/PEEK) with varying surface roughness. The influence of surface roughness and modified fibers on the coating adhesion was studied. Additionally, the effect of the concentrations of nickel sulfate, sodium hypophosphite, pH, and temperature on the deposition rate of the coating was investigated for the three materials. Based on the highest deposition rate, the process parameters were then optimized. The results demonstrated that as surface roughness increased, adhesion between substrate and coating first increased and then decreased. The surface roughness Ra of 0.4 μm produced the highest coating adhesion. Additionally, fiber-reinforced PEEK adhered to coatings more effectively than PEEK did. The mechanism of the difference in bonding strength between different PEEK-modified materials and coatings was revealed. The optimal process parameters were: nickel sulfate: 25 g/L, sodium hypophosphite: 30 g/L, pH: 5.0, and temperature: 70 °C.