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Influence of SO 2 , periodical wetting and corrosion products on the atmosperic corrosion of steel
Author(s) -
Ericsson R.,
Sydberger T.
Publication year - 1980
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.19800310605
Subject(s) - corrosion , rust (programming language) , relative humidity , metallurgy , wetting , materials science , precipitation , leaching (pedology) , acid rain , carbon steel , galvanization , layer (electronics) , chemistry , environmental science , meteorology , composite material , soil water , soil science , physics , organic chemistry , computer science , programming language
Results from laboratory atmospheric corrosion tests on samples of a carbon and a low‐alloy steel, with and without pre‐exposure (1, 3 and 12 months) in an out‐door atmosphere are reported. The laboratory exposure was performed in SO 2 ‐containing (SO 2 ‐supply: 0.4 μg SO 2 · cm −2 · h −1 ) and SO 2 ‐free atmospheres at 90% relative humidity and 22.0° C. The results clearly demonstrate that the influence of atmospheric SO 2 on the instantaneous corrosion rate markedly de‐decreases with increasing pre‐exposure. Comparisons of corrosion rates calculated from out‐door exposures and laboratory exposure tests with and without periodical wettings show that the atmospheric corrosion in the main proceeds during or following periods of atmospheric precipitation or condensation, i. e. under conditions of an apparantly wet rust layer. A synergistic effect of SO 2 and periodical wettings was established. Due to the leaching of sulphate ions from the rust layer, immersion sequences (to simulate rainfall) throughout resulted in lower corrosion rates than the simulation of dew by short spraying sequences. The corrosion of pre‐exposed samples could be related to the amount of sulphate leached from the rust during immersions.