Other

National Research Development Corporation

Alfred C Tseung

Sameer M Jasem

Maurice C Man

David B Hibbert

Ho C Chan

Nagendra P Rasiyah

Anthony I Onuchukwu

Alan S Johnson

Thurairajah Sriskandarajah

Nani B Fouzder

Metal substrates in corrosive environments, such as gas and oil pipelines, are normally prone to embrittlement caused by absorption of the hydrogen atoms cathodically evolved during various corrosion processes. This is substantially prevented by providing an active substance in the vicinity of the metal substrate, and in electrical contact therewith, the active substance being a sulphide or mixed sulphide of a metal of Group Vb, VIb or VIIb of the Periodic Table or of a rare earth metal, especially WS.sub.2 and MoS.sub.2. The active substance is preferably applied as or in a coating on the surface of the substrate, with an overcoating of, for example, a thermosetting resin, preferably being employed for mechanical and environmental protection.

Prevention of hydrogen embrittlement of metals in corrosive environments

The invention relates to lithiated cobalto-cobaltic oxides, especially stoichiometric Co.sub.3 O.sub.4, which have been found to be remarkably efficient electrocatalysts, especially at relatively high total lithium contents of more than 2 atom percent, preferably from 5 to 12 atom percent. The electrocatalysts are especially suitable for oxygen evolution and reduction electrodes and have been found to exhibit long term stability over periods up to 6,000 hours. They are also useful in purely chemical processes such as those involving a decomposition of hydrogen peroxide or peroxyl ions.

Electrocatalyst

An electrochemical cell used to separate gas from a gaseous mixture by reduction of said gas at the cathode and regeneration of said gas at the anode is characterized in that one or more substances formed during the cathodic reduction and/or the anodic regeneration is chemically converted, preferably by catalytic decomposition, to produce further quantities of said gas, the gas formed by both the anodic regeneration and the chemical conversion being recovered as the product. In an especially preferred embodiment a plurality of said cells are used in apparatus for extracting oxygen from the air by using a cathode comprising high surface area graphite powder which reduces oxygen to produce peroxyl ions, each cell being further provided, externally of the cathode compartment, with means for catalytically decomposing the peroxyl ions produced, suitable catalysts being CoFe.sub.2 O.sub.4 or NiCo.sub.2 O.sub.4.

Gas extraction

Metal substrates in corrosive environments such as gas and oil pipelines, are normally prone to embrittlement caused by absorption of the hydrogen which is cathodically evolved during various corrosion processes. This is substantially prevented by providing an active substance in the vicinity of the metal substrate, and in electrical contact therewith, the active substance being one on which cathodic hydrogen evolution occurs in preference to the metal, thereby reducing the amount of hydrogen available for diffusion into the substrate. The active substrate is preferably a sulphide, for example FeS, or mixed sulphide, for example NiCo.sub.2 S.sub.4, and is advantageously applied as a coating on the surface of the substrate, a further coating of, for example, a thermosetting resin, preferably being employed for mechanical and environmental protection.

In chlor-alkali cells, the cathode may consist of a nickel screen carrying 15.6 mg Co.sub.2 NiS.sub.4 bonded by 4.4 mg polytetrafluoroethylene per cm.sup.2.

Method of catalyzing the evolution of gaseous hydrogen

An electrode suitable for use in corrosion conditions is formed with its exposed surface composed of a substantially pore-free material consisting of an acid-resistant, semi-conducting oxide material in a fused glass. Titanium-doped ferric oxide semi-conducting material in a soda-glass or boro-silicate glass is preferred.

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London, United Kingdom

Alfred C Tseung