Passivation of nickel

Willert, H., Investigations of the Corrosion Resistance of a 13%Cr Steel in Aqueous Salt Solutions , Neue Huelle, 11 72 (1966) C.A., 65, 14954b Tousek, J., Passivity of Nickel , Colleclion Czech. Chem. Commun., 31, 3083 (1966) C.A.,... 

In many aqueous solutions nickel has the ability to become passive over a wide range of pH values. The mechanism of passivation of nickel and the properties of passive nickel have been studied extensively—perhaps more widely than for any other element, except possibly iron. In recent years the use of optical and surface analytical techniques has done much to clarify the situation . Early studies on the passivation of nickel were stimulated by the use of nickel anodes in alkaline batteries and in consequence were conducted in the main in alkaline media. More recently, however, attention has been directed to the passivation of nickel in acidic and neutral as well as alkaline solutions. 

Most authorities nowadays accept the view that passivity of nickel, as of most other metals, is due to the formation of a film of oxide or hydrated... 

The alloying elements molybdenum and copper do not, by themselves, enhance passivity of nickel in acid solutions, but instead ennoble the metal. This means that, in practice, these alloying elements confer benefit in precisely those circumstances where chromium does not, viz. hydrogen-evolving acidic solutions, by reducing the rate of anodic dissolution. In more oxidising media the anodic activity increases, and, since binary Ni-Mo and Ni-Cu alloys do not passivate in acidic solutions, they are generally unsuitable in such media. 

Fig. 4.35 Influence of temperature on breakdown of passivity of nickel in H2SO4 + Na2S04 solution (pH 0-4) containing 0-05 m C1 (after Gressmann )...

Nickel oxides and hydroxides play an important role in the passivity of nickel in aqueous solutions, in oxidizing ionic... 

N.D. Greene, The Passivity of Nickel and Nickel-base Alloys, First International Congress on Metallic Corrosion, National Association of Corrosion Engineers, 1961, p 113-117... 

Nickel is active in the Emf Series with respect to hydrogen, but noble with respect to iron. The theoretical potential-pH domains of corrosion, immunity, and passivation of nickel at 25°C are shown in Fig. 23.1 [2], which shows, for example. 

Examples of liquid additives currently in use include bismuth and antimony based additives for passivation of nickel contaminants. A number of solid catalytic additives have been developed that are specific for certain functions. Approximately two-thirds of North American units utilize a noble metal promoter to reduce emissions of CO as well as provide beneficial yield effects. During the early to mid-1980 s, SOX removal additives came into use due to tighter environmental restrictions. A ZSM-5 based additive for octane enhancement and light olefin production was developed during the mid-1980 s and is used commercially. Additives have also been proposed as metal traps especially for vanadium passivation. These solid FCC additives have become an increasingly important tool by which refiners meet yield and environmental requirements. 

Figure 6 Passivity of nickel. XPS spectra of a nickel(lOO) electrode after passivation in 0.1 N H2SO4 at 0.54 V (vs. SHE) for 30 min. (row 1) row 2 shows spectra obtained after ion etching (0.5 keV, 1 min, = 4 x 10 torr). (From Ref 38.)...

Figure 8 Passivity of nickel. Increase of anodic current with time for nickel prepassivated in pH 7.65 borate buffer solution (23% 0) at 0. 4 V (vs. Hg/Hg2S04) for 5 min and then transferred to a pH 1.0 Na2S04 (100% solution for continued polarization at 0.4 V. Also shown is the percentage of 0 detected in the oxide film by SIMS at various times of exposttre to the pH 1.0 Na2S04 solution. (From Ref 57.)...

Figure 9 Passivity of nickel. Induction time for pitting vs. potential of anodization for nickel samples pretreated at 0.3 V in pH 4.0 Na2S04 either with (o) or without (o) 1 M Cl in solution, and pitted in a 0.08 M Cl solution. (From Ref 84.)...

---