Microstructural evolution and characterization of super-induced MgO composite on zinc-rich coatings

The effect of Zn-MgO deposition prepared through direct electrolytic co-deposition on mild steel was studied.The experiment was conducted at current density between 0.5 and 1 A/cm−2. The morphologies of the coated surfaces were characterized using Atomic Force Microscope (AFM), high resolution Nikon Optical Microscope (OPM) and Scanning Electron Microscopy attached with Energy Dispersive Spectrometer (SEM/EDX). The corrosion behavior was studied using linear potentiodynamic polarization method in 3.5% simulated environment. The phase change was evaluated using X-ray Diffractogram (XRD). The microhardness characteristics of the obtained deposits were analyzed with dura scan hardness tester. The stability of the ceramic composite was determined using heat-treatment processes at 200 oC for 4 h. The results show that the structural behavior and corrosion resistance of the coating is dependent on the composite induced particulate and applied current density. It is found that increasing MgO contents beyond optimum level does not cause increase in microhardness progression. A decrease in applied current maximally influences the deposit adhesion characteristics. The enhanced thermal stability of 236.4 HVN for Zn- 20MgO at 0.5 A/cm2 alloy and increase corrosion behavior was thus attributed to its chemical composition, phase content and the synergistic effect of Zn and MgO on the carbon steel

Gel time prediction of polyester resin for lamination of polymer composites

Lamination of fibre reinforced plastics (FRP) and catalytic curing of unsaturated polyester (UP) resin were the major focus of this study. The polyester resin was cured at ambient temperature with methyl ethyl ketone peroxide (MEKP) catalyst, cobalt octoate accelerator and phenol inhibitor. This was used to generate model equations that can predict the gel time of polyester resin when curing additives are added. The gelation was obtained by stirring 20 g of catalysed UP resin weighed into a plastic container until the viscosity suddenly increased. Gel times obtained were subjected to regression analysis and analysis of variance (ANOVA) so as to obtain the best predictive model. The ANOVA result showed that the gel time (Ti) in terms of inhibitor concentration, Ti = 2820i – 6 was the best predictive equation of the gel time with a degree of accuracy of 98.89%; where i is the inhibitor concentration. In the model, catalyst and accelerator are at constant concentrations of 1% and 0.5%, respectively. The model was validated by laminating pilot components using hand lay-up technique. Thereafter, a laminating template was developed that would aid in reducing material wastes and lengthy down time during FRP lamination. This will be useful in increasing productivity and profitability in FRP small scale industry.   Bull. Chem. Soc. Ethiop. 2020, 34(1), 163-174. DOI: https://dx.doi.org/10.4314/bcse.v34i1.1

Nanoparticle Dispersion, Microstructure and Thermal Effect of Multi-doped ZrO2/SiC from Sulphate Induced Electrolyte

Effort to improve the hardness and thermal resilient properties of coating for advanced engineering applications has necessitated this study. Zn sulphate electrolyte was induced with ZrO2-SiC composite particulate at varied current density of 1.5 and 2.0 A/cm2 for 10 minutes. The incorporated composite particles of ZrO2/SiC were varied in other to examine their mechanical responses on zinc electrolyte. The coated films were characterised with scanning electron microscope with attached electron dispersion spectroscopy (SEM/EDS) and atomic force microscopy (AFM). The micro-hardness properties of the coated and thermal aged alloy were determined with high diamond micro-hardness tester. The anti-corrosion progression was examined using linear polarization technique in 3.65% NaCl. From the results, the incorporation of the composite matrix was found to impact significantly on the surface and microhardness properties. The co-deposition of composite submicron on the zinc electrolyte revealed that homogenous grain structure was obtained.To this end, a boost in the performance characteristics was attained due to effective co-deposition parameters in the electrolyte

Electrochemical Oxidation Assessment and Interaction of 2-aminoethanol and N, N-diethylethanamine Propagation in Acidic Medium

Electro�oxidation and inhibitor performance of copper specimens in 1 M hydrochloric acid solu� tion was investigated at room temperature by linear potentiodynamic polarization and gravimetric method in the presence of 2�aminoethanol (A) and N, N�diethylethanamine (D) as an inorganic inhibitor. The effect of the inhibitory concentration on the corrosion behavior of copper was studied over 288 hrs at 298°K. The inhibitory efficiency rise up to 96% for single induced and 98% for synergistic behavior. The adsorption mechanism characteristic was supported by SEM/EDX analysis and adsorption isotherm. From all indica� tion, the inhibitive efficiency of these compounds majorly depends on their molecular structure and concen� tration. The blocking effects of the surface interface were also explained on the basis of the inhibitor active action. 2�aminoethanol and N, N�diethylethanamine inhibits copper in 1 M HCl by strictly affecting both the anodic and cathodic sites. Portion of the surface covered calculated was also found to follow Langmuir adsorption isotherm

Magnesium-based composite by nano-nucleation of β-Mg17Al12 using spark plasma sintering route for advanced structural application

The influence of nano AlN on the microstructural evolution, mechanical (nanohardness, elastic modulus, microhardness, tensile, and yield strength), and tribological performance were examined. The outcome of the research suggested that the AlN inclusion at varying fraction have a direct connection to the enhancement of the investigated properties and a maximum result was achieved by the MgAZ91D-12 wt%AlN nanocomposite. The scanning electron microscope shows the nucleation and dissolution of the dominant β-Mg17Al12 found in the monolithic MgAZ91D following the addition of nano-AlN. Maximum microhardness of 84.0 ± 0.21 HV, nanohardness of 2.2 ± 0.037 GPa, the elastic modulus of 58.333 ± 0.26 GPa, elastic recovery (We/Wt) of 0.228, elastic strain to failure (H/Er) of 0.040, yield pressure (H3/Er2) of 0.0035 GPa, and the lowest plasticity index (Wp/Wt) of 0.7362 were achieved by MgAZ91D-12 wt%AlN. The wear rate of the sintered composite increases with the increase in the load applied but decreases with an increase in the percentage weight fraction of the nano AlN. The coefficient of friction result is observed to be high in unreinforced alloy and decreases as a function of the nano inclusion and the applied load

Characterization of ceramic reinforced titanium matrix composites fabricated by spark plasma sintering for anti-ballistic applications

Titanium has found extensive use in various engineering applications due to its attractive physical, mechanical, and chemical characteristics. However, titanium has relatively low hardness for use as an armour material. ZrB2 was incorporated to the Ti matrix to form a Ti-based binary composites. In this study, powder metallurgy techniques were employed to disperse the ceramic particulates throughout the matrix material then consolidated through spark plasma sintering. The composites were densified at 1300 °C, pressure of 50 MPa, and holding time of 5 min. The microstructure and phase analysis of the sintered composites was carried out using SEM and XRD, while the hardness was determined using Vickers' microhardness tester. The SEM and XRD results confirmed the presence of the TiB whiskers which renowned with the improving the hardness of titanium. The hardness of the composite with 10 wt% ZrB2 showed the highest hardness compared to that obtained for the 5 and 15 wt% ZrB2 composites which was 495 and 571Hv respectively. Keywords: SPS, TiB whiskers, Hardness, Titanium matrix composites, Reinforcemen

Data analysis and study of the influence of deposition power on the microstructural evolution and functionality of metallic phase composite coating

In anticipation for resolution of deterioration catastrophe on metallic materials, researches in the field of corrosion remains. Zn–Ni–NbO2 deposits were obtained on mild steel substrate using D.C. power source. The thermal stability properties of the coatings were determined by micro-hardness evaluations before and after heat treatment at 250 and 350 °C. The surface structure analysis was done by Scanning Electron Microscope and X-ray diffraction while the wear evaluations were obtained and compared. The weight gain and coating thickness were obtained and found to be in correlation with the wear results. The coating developed in this study is recommended for metallic surface improvement engineering applications. Keyword: Zn–Ni, Passive film, Mild steel, NbO

Enhanced corrosion resistance of stainless steel type 316 in sulphuric acid solution using eco-friendly waste product

Literature has shown that different organic compounds are effective corrosion inhibitors for metal in acidic environments. Such compounds usually contain oxygen, nitrogen or sulphur and function through adsorption on the metal surface, thereby creating a barrier for corrosion attack. Unfortunately, these organic compounds are toxic, scarce and expensive. Therefore, plants, natural product and natural oils have been posed as cheap, environmentally acceptable, abundant, readily available and effective molecules having low environmental impact. The corrosion resistance of austenitic stainless steel Type 316 in the presence of eco-friendly waste product was studied using weight loss and potentiodynamic polarization techniques in 0.5 M H2SO4. The corrosion rate and corrosion potential of the steel was significantly altered by the studied inhibitor. Results show that increase in concentration of the inhibitor hinders the formation of the passive film. Experimental observation shows that its pitting potential depends on the concentration of the inhibitor in the acid solution due to adsorption of anions at the metal film interface. The presence of egg shell powder had a strong influence on the corrosion resistance of stainless steel Type 316 with highest inhibition efficiency of 94.74% from weight loss analysis, this is as a result of electrochemical action and inhibition of the steel by the ionized molecules of the inhibiting compound which influenced the mechanism of the redox reactions responsible for corrosion and surface deterioration. Inhibitor adsorption fits the Langmuir isotherm model. The two methods employed for the corrosion assessment were in good agreement. Keywords: Stainless steel, Pitting corrosion, Inhibition, Sulphuric acid, Polarizatio