Rinsing effect of alkaline electrolyzed water on nickel surfaces

The improvement in the surface cleanliness of electroplated nickel by rinsing in alkaline electrolyzed water (AEW) was determined. When the nickel plated sample was rinsed with the AEW, it was found that the amount of residual sulfate ion on the surface of a sample decreased approximately by half compared to one rinsed only with de-ionized pure water. Because nanosize hydrogen bubbles are present in the AEW, and the zeta-potential has a negative value, we then surmised that the mechanism of rinsing was as follows: The sulfate ions are selectively absorbed on the nanosize colloidal hydrogen bubbles, or substituted for anions absorbed on the hydrogen bubbles. The sulfate ions absorbed on the nickel surface then become detached. The detached sulfate ions are absorbed on the surface of the hydrogen bubbles, and negatively charge the hydrogen bubbles. It can be considered that any detached sulfate ions do not re-adhere due to the electrical repulsion force of the negatively charged nickel surface. Thus the sample is efficiently rinsed.