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Austenitic stainless steels are the most favoured construction materials for various components required in chemical, petrochemical, fertiliser and nuclear industries. However, these steels are prone to sensitisation. In the sensitised condition, the steels are quite susceptible to intergranular corrosion and intergranular stress corrosion cracking in chloride and caustic environments resulting in the premature failure of the fabricated components during precommissioning and service periods. The topic of sensitisation has been of interest in studies worldwide. The studies included mechanism of sensitisation, test methods, data generation, and influence of several variables and protection methods. This article covers a review of important contributions to this topic with special emphasis on the influence of metallurgical variables. The present state of understanding is discussed in the following areas: mechanisms, test methods, sensitisation diagrams, influence of chemical composition, cold work and grain size, low temperature sensitisation, modelling and laser surface treatment. The need for further investigation in certain areas is highlighted.

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An attempt was made to improve the localised corrosion resistance of AISI type 304 stainless steel by modifying the surface with duplex coating (titania over ceria). Simple chemical immersion method was adopted for ceria coating, whereas sol-gel route with dip coating method was followed for titania coating. The adherence of the coating was evaluated by ASTM D3359 standard, and the composition of the duplex coatings was evaluated by X-ray photoelectron spectroscopy. The experimental parameters, namely, bath composition, temperature, immersion time and withdrawal speed of the specimens, were optimised to get homogeneous adherent coating. The localised corrosion resistance of ceria, titania and duplex coatings in sea water was studied by potentiodynamic anodic polarisation experiments. These coatings were characterised also by optical and scannning electron microscopes for analysing their pit morphologies. Duplex coated 304 SS exhibited superior corrosion resistance, and the probable reason for the improvement is discussed in detail in this investigation.