Abstract
Specimens of precipitation hardening 16-5-1 stainless steel were solution treated at 1050°C for 1 h followed by aging at temperatures in the range 400 - 750°C for various holding times (1 - 16 h). After heat treatment, two types of corrosion test (accelerated and immersion testing) were conducted in 6% ferric chloride solution. The results showed that the pitting corrosion resistance was affected by austenite content, δ ferrite and precipitation of molybdenum and chromium carbides. Three critical temperature ranges were identified, which were related to the phases formed: (a) high corrosion rate at 475°C (δ ferrite and Mo
2
C); (b) low corrosion rate at 550 - 625°C (reversed austenite and Laves phase); (c) intermediate corrosion rate at 750°C (Cr
23
C
6
and TiC). The morphology of the pitting was dependent on the form of the δ ferrite and carbides.