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, These surfaces are in fact covered with a thin oxyhydroxide film known as ''the passive film.'' Zeta potential depends on the solution composition 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 cleaning treatments and the industrial finish conditions, the zeta potentials range as follows: GRAPHICS Measurements were also performed in chloride-containing media after an ethanol cleaning, At pH higher than the isoelectric point, the zeta potential also depends on the finish conditions. After an ethanol cleaning, one finds GRAPHICS These results are discussed with respect to the properties of the passive film/solute interface, It is shown that the isoelectric point depends on the surface condition of the steel and ranges around ph 4, indicating a negative surface charge for neutral electrolytes. (C) 1995 Academic Press, Inc.