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

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 x 10(3) to 3.0 x 10(4), with adding similar to 6 x 10(7) bubbles/mL of air-nanobubbles to the tested liquid of 0.25% CuCl2 solution at 40 degrees 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.