Sulphurous acid + calcium bisulphite

These corrosion data are mainly based on results of general corrosion laboratory tests, carried out with pure chemicals and water solutions nearly saturated with air (the corrosion rate can be quite different if the solution is free from oxygen).

All concentrations are given in weight-% and the solvent is water if nothing else is shown. The corrosion data apply to annealed materials with normal microstructure and clean surfaces, throughout.

Conc. H₂SO₄ %	1-2
Conc. Ca(HSO₃)₂ %	1-5
Temp. °C	140
Grade or type of alloy:
Carbon steel	2
13 Cr	2
Alleima® 1802	0
Alleima® 3R12	1	The given values are for the liquid phase and
Alleima® 3R60	0	the air-free gaseous phase. If air is present,
18Cr13Ni3Mo ¹⁾	0	attacks by sulphuric acid can occur in the
17Cr14Ni4Mo ²⁾	0	gaseous phase. The values are also applicable
Alleima® 2RK65 ('904L')	0	when calcium bisulphite is replaced by
Sanicro® 28		magnesium bisulphite, sodium bisulphite or
254 SMO		ammonium bisulphite.
654 SMO
SAF™ 2304
SAF™ 2205
SAF™ 2507
Titanium (CP Ti)	0

¹⁾ ASTM 317L, e.g. Alleima® 3R64
²⁾ EN 1.4439, e.g. Alleima® 3R68

Symbol clarification

These corrosion tables use a number of symbols, having the following meanings:

Symbol	Description
0	Corrosion rate less than 0.1 mm/year. The material is corrosion proof.
1	Corrosion rate 0.1—1.0 mm/year. The material is not corrosion proof, but useful in certain cases.
2	Corrosion rate over 1.0 mm/year. Serious corrosion. The material is not usable.
p, P	Risk (severe risk) of pitting and crevice corrosion.
c, C	Risk (Severe risk) of crevice corrosion. Used when there is a risk of localised corrosion only if crevices are present. Under more severe conditions, when there is also a risk of pitting corrosion, the symbols p or P are used instead.
s, S	Risk (Severe risk) of stress corrosion cracking.
ig	Risk of intergranular corrosion.
BP	Boiling solution.
ND	No data. (Used only where there are no actual data to estimate the risk of localised corrosion instead of p or s).

Disclaimer: Laboratory tests are not strictly comparable with actual service conditions. Accordingly, Alleima makes no warranties, express or implied, and accept no liability, compensatory or consequential, for the performance of different materials in individual applications that may be based on the information provided in this publication.