Abstract
In general pure organic environments are not very corrosive. AISI types 304L and 316L stainless steels are widely used to handle them. However, in the chemical industry the corrosive action of organic environments can become rather complicated because process mixtures frequently contain inorganic acids, corrosive catalysts (e.g. sulphuric or hydrochloric acids), salts, solids, etc.. Furthermore, contaminants like oxygen, ferric or cupric ions have to be considered since they tend to shift the redox potential of the mixture to oxidizing. The presence of chlorides usually have disastrous effects on the corrosion resistance of standard stainless steels. Under more severe operating conditions good corrosion performance can be achieved with high alloyed stainless steels and nickel based alloys.
The paper describes the corrosion behaviour of three nickel based alloys 59, B-2 and B-4 and a high alloyed austenitic stainless steel alloy 31 in different organic environments containing 2-5% sulphuric acid or hydrochloric acid and analyses the effect of oxidants and chlorides. B-alloys exhibit the best corrosion resistance under reducing conditions. Alloy 31 requires a threshold oxidizing capacity for passivity, showing best performance in the presence of oxidants. Alloy 59 is the most universal alloy performing well under oxidizing and reducing conditions and resisting to high chloride levels.
