Inhibiting flow-accelerated copper corrosion under liquid jet impingement by utilizing nanobubbles

Abstract

Flow-accelerated corrosion can be very destructive, leading to rapid loss of component efficiency and eventual failure of the system; however, finding inexpensive, effective, and chemically benign inhibitors is still challenging. This paper studied for the first time the use of nanobubbles/ultrafine bubbles as a “green” functional nanostructured material for inhibiting flow-accelerated corrosion under the impingement of a turbulent liquid jet. We examined the corrosion inhibition of the copper specimen for 5 h in the flow regime at a Reynolds number of from 6.1 × 103 to 3.0 × 104, with adding ∼6 × 107 bubbles/mL of air-nanobubbles to the tested liquid of 0.25% CuCl2 solution at 40 °C. We measured weight losses, analyzed microstructure using SEM, and acquired maximum erosion depths and roughness curves of tested copper specimens. We found that nanobubbles mitigated flow-accelerated corrosion under jet impingement. The inhibition effectiveness was more significant at higher jet velocity and longer test time, with up to 43.9 ± 0.1% and 69.5 ± 1.8% based on weight losses and erosion depths, respectively. Nanobubbles play a role in reducing wall shear stress on the copper surface, likely by generating bubble mattresses. We suggest that nanobubbles inhibit the corrosion in highly erosive/corrosive turbulent conditions where most inhibitors could not work well.