Role of ethylamines on the electrochemical behaviour of Fe-Ni alloy films

• Published in: Journal of applied electrochemistry 2001-11, Vol.31 (11), p.1227-1233
• Main Authors: ARAVINDA, C. L, MURALIDHARAN, V. S, MAYANNA, S. M
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemistry; Electrochemistry; Electrodeposition; Exact sciences and technology; General and physical chemistry; Metallic coatings; Metals. Metallurgy; Production techniques; Study of interfaces; Surface treatment
• ISSN: 0021-891X
• DOI: 10.1023/A:1012781325689

Cyclic voltammetric experiments were carried out on platinum in acidic solution (pH 3) containing ferrous sulfate, nickel sulfate and ethylamines (EtNH sub 2 , Et sub 2 NH, Et sub 3 N). Spectral ultraviolet absorption studies indicate the complexation of both Fe exp 2+ and Ni exp 2+ ions with ethylamines. The results under transient polarisation conditions indicate the reduction of Fe exp 2+ ions through the intermediate species FeOH exp + , with second electron transfer as a slow step. The higher charge transfer rate of FeOH exp + over NiOH exp + reduction causes the anomalous codeposition of Fe-Ni alloy film. Among the ethylamines, Et sub 3 N considerably assists the alloy deposition process. A gradual variation in free energy of alloy formation with Fe exp 2+ :Ni exp 2+ (mol:mol) in the bath suggests the formation of an alloy intermediate phase rich in iron. Stripping voltammetric curves indicate the preferential dissolution of iron from iron rich alloy intermediate phase. X-ray diffraction studies further confirm the phase to be b.c.c. Fe-Ni alloy. The extent of corrosion of the Fe-Ni alloy film in the presence of ethylamines is in the following order: Et sub 3 N > Et sub 2 NH > EtNH sub 2 .