EFFECTS OF FLUCTUATING HEAT TREATMENT OPERATIONS ON CORROSION RESISTANCE OF AUSTENITIC STAINLESS STEEL SAMPLE IN SULPHURIC ACID SOLUTION

Abstract

Corrosion performances of austenitic stainless steel subjected to various cyclic heat treatment operations of normalisation, annealing and solution-quenching have been evaluated. Samples of the as-received material (hot-rolled austenitic stainless steel) were subjected to five cycles of heat-treatment consisting of normalisation soaked for 1 hour and without soaking at 1000°c,annealing soaked for 1 hour and without soaking at 1000ne and solution-quenching soaked for I hour and without soaking at 1000°e. Estimation of corrosion rates from weight loss measurements was carried out using chemical weighing balance of model Mettler AE 160. The results show that corrosion rates decrease with increase in exposure time for as received and heat-treated samples. A general increase in electrode potentials is observed for all the specimens from-235mV (SCE) to-58 mV (SCE) at the exposure periods above 240 hours. The electrode potentials for all the samples remain within the range of-58mY (SCE) and 8mY (SCE) at the exposure periods between 250 and 750 hours. It is concluded that corrosion resistance of austenitic stainless steel subjected to normalization! annealing and solution-quenching at elevated temperature without soaking period at 1000°c is superior to that which was soaked for 1 hour at the temperature. This was attributed to the fact that austenitic stainless steel microstructure remain as austenitic single phase after cooling to room temperature.