Cobalt coatings are considered a suitable alternative to chromium coatings due to their desirable properties and environmental compatibility. In this study, by adding phosphorus as an alloying element and reinforcing nanoparticles of ZrO2 and CeO2 to the cobalt coating More
Cobalt coatings are considered a suitable alternative to chromium coatings due to their desirable properties and environmental compatibility. In this study, by adding phosphorus as an alloying element and reinforcing nanoparticles of ZrO2 and CeO2 to the cobalt coating matrix, amorphous Co-P-ZrO2-CeO2 and Co-P coatings were produced on a ST37 steel substrate using electrochemical deposition. The effect of current density on the morphology of the coatings was investigated by scanning electron microscopy (SEM), and the weight percentages of elements present in the coatings were analyzed using EDS analysis. Microhardness and corrosion resistance were also examined. The addition of reinforcing nanoparticles to the cobalt-phosphorus alloy matrix increased the hardness of the nanocomposite coatings. It should be noted that increasing the current density up to an optimal level increases the hardness, and then decreases it. The results of the Tafel and EIS analyses on the nanocomposite coatings indicate an increase in corrosion resistance with an enhancement in current density up to 100 mA/cm2 for both alloy and nanocomposite samples, which is due to an increase in the weight percentage of phosphorus and the formation of a surface protective layer. In addition, the presence of reinforcing nanoparticles in the matrix prevents corrosive medium from reaching the coating surface, improving its corrosion resistance.
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In this research, two types of composite coatings based on epoxy paint reinforced by TiO2 nano and micro particles and TiO2 particles hydrophobicized by polysiloxane were prepared separately with concentrations of 1, 2, 3, 4 and 5% by weight to improve the properties of More
In this research, two types of composite coatings based on epoxy paint reinforced by TiO2 nano and micro particles and TiO2 particles hydrophobicized by polysiloxane were prepared separately with concentrations of 1, 2, 3, 4 and 5% by weight to improve the properties of epoxy paint. and in order to investigate their behavior, they were applied on API 5L X52 steel and then their properties were investigated by conducting corrosion and wear tests. The thickness of the coatings was checked by a digital thickness gauge. The corrosion resistance behavior of the coatings was evaluated using the polarization method in 3.5% NaCl solution. The results of the corrosion test showed that by adding and increasing the concentration of reinforcing particles in the coatings, the corrosion resistance was improved, and also the composite coating of epoxy paint with 5% by weight of the hydrophobic TiO2 reinforcement showed better corrosion resistance than other samples. A scanning electron microscope (SEM) equipped with EDX was used to examine the morphological properties of the surface. In order to check the dispersion of micro particles in the field of coating, Map analysis was taken from the samples. The results obtained from Map analysis have shown the appropriate and uniform distribution of hydrophobic particles in the field of epoxy coating. The wear resistance of the coatings was performed by the bullet test machine on the disc. The results of the abrasion test showed that by adding and increasing the concentration of reinforcing particles in the coating, the abrasion resistance of the coating increased, but by comparing the epoxy composite samples, it was found that the hydrophobicity of the reinforcing particles had no effect on the abrasion resistance.
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In the present study, Ni-P coatings were successfully deposited on mild steel surface via electroless plating. The optimization of heat treatment parameters (i.e., temperature and time) based on response surface methodology has been systematically studied in order to ob More
In the present study, Ni-P coatings were successfully deposited on mild steel surface via electroless plating. The optimization of heat treatment parameters (i.e., temperature and time) based on response surface methodology has been systematically studied in order to obtain the simultaneously improvement in corrosion resistance and hardness. X ray diffraction analysis (XRD), scanning electron microscopy (SEM) and EDS analysis were used to characterize the coatings. The corrosion behavior of the coatings was evaluated using Tafel polarization method in 3.5 wt.% NaCl aqueous solution. It has been found that the as-plate coating has an amorphous structure and heat treatment caused to precipitate Ni3P phase as well as to form crystalline nickel phase. The corrosion resistance and hardness are strongly affected by heat treatment. By increasing the time and temperature corrosion resistance and hardness firstly increased and then decreased. The results showed that low corrosion rate less than 2 mpy and high hardness value more than 900 vickers were achieved by heat treatment at 450° C for 75 min.
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