Performance of Steels against Corrosion in Peracid Bleach Media, 2004 11th International Symposium on Corrosion in the Pulp and Paper Industry

As a pollution control strategy, paper industry is replacing chlorine and its compounds as bleach chemicals by oxygen, peroxide, ozone, peracids etc. The consequential changes in the chemical constitution of bleach plant liquors are expected to affect the corrosivity of the media. This, in turn, may question the credibility of the existing plant machinery. One can then expect fabrications from new bleach plant metallurgy. Keeping these aspects in view, an attempt was made to investigate the performance of mild steel, austenitic stainless steels 304L, 316L, 317L and a duplex stainless steel 2205 against corrosion in peracid bleach media. These materials were subjected to long term immersion test and electrochemical polarization tests, at room temperature and 50°C, in peracetic acid (Pa), Caro’s acid (Px) and mixture of Pa and Px (Pxa) solutions. The tests showed Pa to be most corrosive followed by Pxa and Px. Among the tested materials, mild steel showed very high degree of general corrosion in all the test solutions even at room temperature and so can’t be considered a candidate material for machines handling peracids. Stainless steels showed varying degree of corrosion resistance against localized corrosion. Considering the data from present tests along with the mechanical properties, fabrication aspects and overall cost, effort has been made to suggest the appropriate material of construction.