Long-term corrosion tests of materials for thermal decomposition of sulphuric acid

The corrosion resistance of tubes of Incoloy 800 and AISI 310 SS has been studied in a mixture of air and H₂SO₄ vapours at 1 bar pressure. The duration of the test was one year (8500 h). The temperatures of the tubes ranged from 400 to 700°C for SS AISI 310 and from 400 to 900°C for Incoloy 800. The extent of the attack was determined by measuring the scale thickness and the penetration depth on cross-sections of samples taken from several zones of the tubes. X-ray diffraction and S.E.M. X-ray microanalysis techniques were used.