Preparation and characterization of Ni–SiO₂ composite coating on pipeline inner surface

A novel Ni–SiO₂ composite deposition layer was created in the inner wall of the pipe adopting a new type of brush plating device, and the properties of the deposition layer were characterized; experimental results show that the nanocomposite deposition layer significantly improves the mechanical properties and corrosion resistance of the inner wall of the pipe. Firstly, under the conditions of nanoparticle addition (40 mL/L, 60 mL/L, 80 mL/L), working voltage (12 V, 14 V, 16 V) and pH (5, 7, 9), the hardness value and surface morphology of deposited layer were investigated through orthogonal experiments, and the optimal process variables were preliminarily determined. Orthogonal experiment results show that when the addition of nanoparticles is 80 mL/L, the voltage is 14 V, and the pH value is 7, the Ni–SiO₂ nanocomposite deposition layer has high microhardness (618.6 HV) and good microscopic morphology. According to the analysis of the results of the orthogonal experiment, the addition amounts of nanoparticles is the main influencing factor, so the control variable method is utilized to investigate the effect of the addition amounts of nanoparticles on the properties of the deposited layer. The results show that when the amounts of nanoparticles added is 80 mL/L, the surface of deposited layer is smoother, denser and less defective. Moreover, the deposited layer has excellent mechanical property and corrosion resistance. In a solution of 3.5% sodium chloride, −0.78 V is the corrosion potential, 1.93 × 10⁻⁵ A·cm⁻² is the corrosion current density, and 0.22 mm·a⁻¹ is the corrosion rate.