Corrosion behavior of a stainless steel with heat transfer in nitric acid solutions under reduced pressure environments

Corrosion behavior of the nitric acid resistant type 304L stainless steel with heat transfer conditions has been evaluated in nitric acid solutions simulating reduced pressure evaporators for acidic liquid waste streams in the reprocessing plant. A testing rig was constructed so as to avoid the gasket sealing the stainless steel specimen to the test cell containing nitric acid solution, which had been perceived to contribute to an erratic test result due to the effect of crevice corrosion. Corrosion behavior was monitored electrochemically by measuring the corrosion potential and polarisation resistance in order to shorten testing time to reduce a risk to produce crevice corrosion. Testing conditions were characterised by metal surface temperature and solution temperature, with and without boiling simulating reduced pressure evaporators for liquid waste streams. Test results confirmed that cooler solution temperature at the metal surface with heat transfer led to consistent decrease in corrosion rate compared with isothermal conditions regardless of presence of boiling or not in nitric acid solutions containing substantial amount of nitrate salt. (author)