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The influence of sodium chloride on the atmospheric corrosion of steel
Author(s) -
Ericsson R.
Publication year - 1978
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.19780290604
Subject(s) - relative humidity , corrosion , sodium , chloride , humidity , atmosphere (unit) , chemistry , sulfur dioxide , metallurgy , materials science , inorganic chemistry , meteorology , physics
The influence of sodium chloride on the atmospheric corrosion of mild steel has been studied. Samples covered with sodium chloride crystals (8 m̈g NaCl · cm −2 ) have been exposed to an SO 2 ‐free atmosphere at different relative humidities. The combined effect of sodium chloride crystals on a steel surface and sulphur dioxide in the atmosphere has been investigated at an SO 2 ‐supply of 1 m̈g SO 2 · cm –2 · h –1 (1 ppm SO 2 ). The corrosion attack was followed by periodic weighings. The corrosion products formed have been studied using the SEM‐technique. On exposure of samples with sodium chloride in an SO 2 ‐free atmosphere the extent of corrosion increased with increasing relative humidity from 58% to 90%, interrupted by a sharp minimum at about 87% relative humidity. The SEM‐studies showed that tower shaped corrosion products were formed at a high relative humidity while filiform corrosion appeared when the relative humidity was lowered. At 90% relative humidity more corrosion was observed with clean steel samples and an SO 2 ‐supply of 1 m̈g ·cm –2 ·h –1 than with sodium chloride crystals on the surfaces (8 m̈g NaCl ·cm –2 ) in the absence of SO 2 . In the combined influence of sodium chloride on the steel surfaces and sulphur dioxide in the atmosphere a synergic effect was noticed at 90% relative humidity. At 70% relative humidity no influence of an SO 2 ‐supply of 1 m̈g SO 2 ·cm –2 ·h –1 on the corrosion of steel samples with sodium chloride crystals on their surfaces could be observed.