The temperature dependencies of susceptibility of 654SMO and 316L stainless steels to pitting

Performed investigations by cyclic thermometry in a solution containing 1 per cent H₂SO₄ by weight admixed with chloride ions in 0.2 per cent quantity by weight at 553K have shown that 654SMO steel is not susceptible to pitting, while 316L steel is intensively attacked in investigation conditions. On cyclic thermograms for 316L steel three temperature zones can be distinguished. The first zone is the zone of resistance to pitting. In the third temperature zone rapid development of pits is observed. The second intermediate temperature range includes the process of initiation and formation of pits. The temperature of pitting corrosion of 316L steel depends linearly on the applied polarisation. The temperature determined by extrapolation for a polarisation equal to zero is the measure of resistance to pitting corrosion. The pitting corrosion temperature determined in this way is related to stationary conditions, with no polarisation.