THE INFLUENCE OF VARIOUS MAJOR AND MINOR ALLOYING ELEMENTS ON THE CORROSION OF AN FE-40-PERCENT-CR SUPERFERRITIC STAINLESS-STEEL IN SULFURIC-ACID

The corrosion resistance of an Fe-40%Cr superferritic alloy containing various major and minor alloying additions, e.g. nickel, molybdenum, aluminium, zirconium, nitrogen, niobium, titanium and ruthenium, as we ll as various combinations of them, was investigated in dilute sulphur ic acid. Although small nickel and molybdenum additions alone cannot c ause spontaneous passivation of the Fe-40%Cr alloy to which they are a dded, a combination of these two alloying elements result in an Fe-40% -Cr superferritic stainless steel which can passivated spontaneously i n dilute sulphuric acid. Further additions of minor alloying elements like Ti, Nb, Ru and N have an influence on the time required to achiev e spontaneous passivation and the final open-circuit potential eventua lly reached. Further additions of Al and Zr to the Fe-40%Cr-2%Ni2%Mo a lloy did not have much of an effect on the final open-circuit potentia l reached, and only affected the time required before this potential w as reached in each case.