jamieg1;
What are your process conditions regarding exposure to sulfide? I can tell you that the two main benefits derived from PWHT of carbon steel are the reduction of residual stresses from welding, and the reduction of hardness in the base metal heat affected zone (HAZ).
If the corrosion process involves stress corrosion cracking or stress-assissted corrosion, PWHT would help to reduce suscetibility. Otherwise, PWHT would have no impact on general corrosion resistance of the vessel.