-
Sodium Hypochlorite is widely used as a sanitiser in water systems and is the main constituent of household bleach, at around 5.25 %. It is aggressive to stainless steels. Pitting or crevice corrosion can occur on most stainless steel grades. Pitting corrosion has been reported from household bleach spills on stainless steel, (304 type), sinks in domestic environments. There is an additional risk of stress corrosion cracking, (SCC), at higher temperatures.
-
Dry or liquefied sulphur dioxide gas should not be aggressive towards stainless steels. When dissolved in water it forms sulphurous acid, H2SO3, and is mildly corrosive. Oxidation of the acid to sulphuric acid can be a corrosion risk to stainless steels.
-
Sulphuric acid is oxidising when concentrated, but is reducing at low and ‘intermediate’ concentrations. Most stainless steel types are resistant at either low or high concentrations, but not at intermediate concentrations. Corrosion resistance of stainless steels also depends on aeration and oxidising conditions and the velocity of flow in pipework systems. ‘Battery acid’ is sulphuric acid with a weight percentage concentration of over 35 %, (specific gravity of 1.28).
