Corrosion resistance of UNS S41426 stainless steel in acid media and its relation to chemical partition and austenite fraction

•Corrosion behavior of heat-treated UNS S41426 has been investigated.•Heat-treatments above AC1 promotes austenite reversion and hardness decrease.•Chemical partitioning of Ni and Cr plays an imperative role in corrosion behavior.•Cr-depleted areas promote anodic peak separation and increased corrosion rate.•Ni-rich areas reduce corrosion rate in immersion tests due to austenite ennoblement. The present work evaluates the impact of tempering treatment on austenite reversion and corrosion resistance of UNS S41426 in 0.5 M H2SO4 solution. Higher austenite fraction was related to higher tempering temperature, engendering lower hardness degrees. Despite a reduction in corrosion rates in immersion tests, Ni-rich austenite decreased corrosion resistance in more oxidizing environments. Cr-depleted regions created a secondary anodic peak in polarization tests. Chemical partitioning is presented to be the main feature that influences corrosion in supermartensitic stainless steel. Finally, tempering at 650 °C presented the best results as it had ten times less corrosion rate than as-quenched state.