Electrochemical hydrogenation and corrosion behaviour of LaCo 4.8 M 0.2 alloys

Hydrogen absorption properties and the corrosion characteristics of three LaCo 4.8 M 0.2 alloys (where M ≡ antimony, magnesium or bismuth) have been investigated using electrochemical techniques. Absorption of hydrogen and corrosion behaviour of LaCo 4.8 M 0.2 alloys have been compared with LaCo 5 intermetallic compound. Typical potentiokinetic polarisation curves in 6 M potassium hydroxide solution showed that modification of LaCo 5 by partial substitution of antimony, magnesium or bismuth for cobalt resulted in lower anodic currents in the passive range. The substitution does not significantly affect the shape of potentiokinetic polarisation curves in 0.5 M sulphate solutions for pH 2 and 7. Partial substitution of cobalt with bismuth in LaCo 5 alloy increases the effectiveness of absorption of cathodically evolved hydrogen in strong alkaline solutions.