More than ordinary rinsing using pure water, cathode water obtained by electrolysis of dilute potassium carbonate aqueous solution (alkaline electrolyzed water: AEW) exhibits a stronger rinse effect for elimination of remaining sulfate ions when rinsing nickel-plated surfaces. This rinse effect was recognized even for AEW that was used 24 h after it was produced, but not 1 week after. Behaviors of hydrogen nanobubbles observed by dynamic light scattering revealed nanobubbles of about 128-nm diameter even 24 h after generation. The Ostwald ripening phenomenon was observed. Hydrogen nanobubbles in an open system changed: some shrank because of ripening, later dissolving in the aqueous solution and disappearing; others showed swelling and expansion. One week later, few nanobubbles smaller than 300 nm were observed. Rinse effects by AEW, which are attributable to the actions of hydrogen nanobubbles generated in AEW, occur because sulfate ions are cleaned and removed from the nickelplated surface.