Mechanical properties and aqueous corrosion behaviour of the ferritic Fe-Cr-V alloys

Corrosion behaviour of the Fe-17Cr-(2-5)V and Fe-23Cr-(2-5)V alloy systems in 5% sulphuric, 5% hydrochloric and 0.5% sodium chloride solutions has been investigated by means of the immersion test and potentiodynamic measurements. Results are also given on the effect to Mo or Ni addition on the corrosion resistance of these alloy systems. Immersion test reveals that the additions of 2 and 5% V have little influence on inhibiting dissolution of the Fe-17Cr alloy in sulphuric and hydrochloric solutions. However, addition of 1% Mo to the Fe-17Cr-2V alloy has been shown to enhance resistance to corrosion in reducing acid solutions. Moreover, additions of 1-2% Ni to the Fe-17Cr-(2-5)V system also exhibit a similar inhibiting effect on alloy dissolution but it is less pronounced than with Mo addition. From cyclic polarization curves it is evident that the Fe-17Cr-(2-5)V system with or without Mo or Ni addition is subject to pitting corrosion due to its low breakdown potentials and large hysteresis loops. The immersion and potentiodynamic techniques have shown that the Fe-23Cr-3V-2Mo alloy exhibits the highest resistance to reducing acids and sodium chloride solution among the alloys studied.