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Investigation of corrosion products formed on C35-AlMgSi0·5 friction welds during natural weathering in marine climate

 
: Schneider, M.; Langklotz, U.; Labus, M.; Arnold, B.; Michaelis, A.

:

Corrosion engineering, science and technology : CEST 47 (2012), No.4, pp.312-319
ISSN: 1478-422X
English
Journal Article
Fraunhofer IKTS ()
AlMgSi0·5; atmospheric corrosion; C35; friction welds; microelectrochemistry

Abstract
AlMgSi0·5-C35 friction welds were exposed to marine climate in Helgoland for 2 years. The corrosion products formed on the samples were investigated in view of their electrochemical reactivity, morphology as well as chemical and phase compositions. Various types of corrosion attack (atmospheric corrosion, bimetallic corrosion and pitting corrosion) were verified. Generally, the corrosion attack of C35 is stronger than that of aluminium. Aluminium serves as a sacrificial electrode only close to the welding plane. The rust scale formed on the steel side of the friction weld mainly consists of γ-FeOOH and α-FeOOH. Despite the significant chloride concentration inside the rust layer, no β-FeOOH was found. As it is well known, only the γ-FeOOH phase is electrochemically high ly reactive and can be reduced to Fe 3O 4, depending on the polarisation potential. The reduction of γ-FeOOH is associated with an increase of oxygen reduction.

: http://publica.fraunhofer.de/documents/N-207003.html