Hydrogen surface films

Concentrated nitric acid renders the metal passive , i.e. chemically unreactive, due to formation of a thin oxide surface film (which can be removed by scratching or heating in hydrogen). 

Beryllium is readily attacked by most acids and, being amphoteric, is slowly attacked by caustic alkalis with the evolution of hydrogen. As might be anticipated, in view of the controlling influence of the surface film of beryllia on corrosion behaviour, concentrated nitric acid has little effect on beryllium , while the dilute acid results in slow attack. Hot acid is much more reactive. Nitric acid is in fact often used to pickle-off residual mild steel from hot-extruded clad beryllium. 

As the hydrogen ions replace alkali (R) ions a surface film forms which has properties different from the massive glass. This film swells, acting as a barrier to further diffusion of ions into, and out of, the surface, inhibiting further attack. If this layer dries out, the thin film gives characteristic irridescent interference colours. 

Fig. 16. Example of a A s.p. = f(t) relation, manifesting surface potential changes in a nickel-hydrogen system as a function of time and amount of hydrogen introduced onto a surface of a nickel film deposited at liquid nitrogen temperature hydrogen-nickel film interactions were studied by Tompkins-Eberhagen static condenser method at liquid nitrogen temperature. After Dus (60). Each dose of H2 — 2.5 X 10 molecules.

Spectral Transparence Starting from 230 nm -oc 4-Isopropylphenoxy Photooxidable Groups Presence of Labile Tertiary Hydrogen Atoms Photooxydation and Photoreticulation Processes Surface Film Modification ... 

The main factors governing hydrogen embrittlement are the metal surface films that can restrict hydrogen absorption, the effect of electrical discharge machining that may... 

Hard amorphous carbon films may either be fully amorphous or contain tiny diamond crystallites. Hydrogen-free films may be deposited on surfaces from graphite by laser ablation or ion sputtering. Hydrogen-containing films are also possible. 

Fig. 5. Calibration measurement of solid hydrogen film layer thickness via energy loss of a particles [27,28]. Americium a source is embedded on the surface of the gold-plated copper substrate, onto which hydrogen thin film is deposited by releasing the gas through porous sintered metal (diffuser). Silicon detector, mounted on the vertically movable diffuser, measured the a particle energy loss in the film, which is converted the thickness using the stopping power...

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