ZETA-POTENTIAL MEASUREMENTS ON PASSIVE METALS

In this study, one shows that the zeta potential can be determined on stainless steel sheet surfaces by streaming potential measurements, Th ese surfaces are in fact covered with a thin oxyhydroxide film known a s ''the passive film.'' Zeta potential depends on the solution composi tion and the surface final conditions, The zeta potentials on AISI 304 stainless steel with 2B and BA surface finishes were measured in KNO3 -containing me dia for several cleaning treatments. Depending on the c leaning treatments and the industrial finish conditions, the zeta pote ntials range as follows: GRAPHICS Measurements were also performed i n chloride-containing media after an ethanol cleaning, At pH higher th an the isoelectric point, the zeta potential also depends on the finis h conditions. After an ethanol cleaning, one finds GRAPHICS These re sults are discussed with respect to the properties of the passive film /solute interface, It is shown that the isoelectric point depends on t he surface condition of the steel and ranges around ph 4, indicating a negative surface charge for neutral electrolytes. (C) 1995 Academic P ress, Inc.