Nonaqueous Electroless Chromium Plating Method
ROCKETDYNE CANOGA PARK CA
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The method involved treatment of chromium salts with a variety of reducing agents. Lithium borohydride in tetrahydrofuran-diethyl ether reduces chromic chloride to the chromous state on mixing, followed by a slower reaction presumed to be the deterioration of chromous borohydride to a chromium boride of not well-defined composition. The boride forms as a black nonadherent plate preferentially on metal substrates. Trialkylborohydride salts in tetrahydrofuran reduce chromic chloride immediately to colloidal elemental chromium which redissolves if excess chromic chloride is present to form chromous chloride. Dialkylborohydride salts under like conditions produce chromous chloride which is then further reduced to the elemental form. Substitution of either borohydride ion or dimethylborohydride ion with a cyano group resulted in a decrease in the strength of the reducing agent such that chromic chloride could be reduced only to the chromous stage in tetrahydrofuran.
- Fabrication Metallurgy