Structural analysis and intergranular corrosion tests of AISI 316L steel.

Pure AISI 316L steel is investigated after solution heat treatment (1050 degrees C/H(2)O) and structural sensitization (650 degrees C). Two quite different intergranular corrosion tests are used to determine the degree of structural sensitization due to the precipitation of secondary phases along the grain boundaries (mainly the M(23)C(6) and sigma-phase): the oxalic acid etch test and the electrochemical potentio-kinetic reactivation test. Generally, the dissolution of chromium-rich carbides (M(23)C(6)) is provoked by oxalic acid etch tests, whereas the chromium-depleted zones, in the vicinity of chromium-rich carbides (M(23)C(6)), are attacked by electrochemical potentio-kinetic reactivation tests. Both intergranular corrosion tests are used to determine the maximum degree of structural sensitization. Thus structural analysis by carbon replicas reveals the Laves phase, and both the M(23)C(6) and (Cr,Mo)(x)(Fe,Ni)(y) phases. The results of intergranular corrosion tests are related to the findings of the structural analysis.