No abstract

Reformation of the passive film on 304 stainless steel (UNS S 30400) was investigated with a scratch test. Regrowth of the passive film was measured by recording the current that resulted from forming the scratch. Charge consumed during the reformation of the film was compared to wear produced by the scratch. The current density from an incremental area of the scratch was extracted from the measured current transients using the width of the scratch as a function of time. The maximum current density and the charge density were dependent linearly on the area fraction of bare surface. Other parameters used in the model of current transients did not change as the area fraction of bare surface changed. Results showed the passive film remained adherent to the surface of the stainless steel during the rubbing mode of wear.

In order to obtain an understanding of the mechanism of chromium particle occlusion in electrodeposited stainless‐steel‐type coatings, the U.S. Bureau of Mines has studied the effect of chromium particles on nickel electrodeposition. The chromium particles catalyzed nickel electrodeposition on a vitreous carbon surface. Chromium particle additions, when added to Watt's‐type electrolytes, of 0.33M,0.67M,normaland 1.00M NiSO4 , shifted the nickel reduction wave to more positive potentials on a vitreous carbon surface. From rotating cylinder electrode studies it was concluded that nickel deposition with or without chromium particles is a kinetically limited rather than mass‐transfer‐limited process. Electrochemical impedance spectroscopy experiments with and without chromium particles verified the rate‐determining step proposed by Epelboin, with the Ni+(ads) limiting the nickel electrodeposition. The chromium particles appear to enhance the formation of this Nifalse(normaladsfalse)+ intermediate.

No abstract

No abstract