No abstract

Carbon and low alloy steels are the most commonly used construction materials for oil and gas pipelines. In order to improve their performance, various types of coatings are frequently applied on them. Electroless nickel composite coatings containing nano-particles are widely used on steel substrates. In this paper, CO2 corrosion of X70 carbon steel coated with Ni-P and Ni-P-nanoSiO2 in 3%Wt NaC1 electrolyte, saturated with CO2 at 85°C and pH 6.5 in 1bar CO2 pressure for 72 h, was investigated and the results were compared against each other. SEM and XRD techniques were used for investigating the corrosion products morphology and composition, respectively. In addition, the corrosion process was studied using EIS technique. The experimental results showed that the formation of FeCO3 protective film on coated samples was limited. Moreover, the addition of SiO2 nano-particles to Ni-P coating improved corrosion resistance of the substrate, which also showed the ability of nano-particle addition to the Ni-P coating in decreasing the corrosion rate.