Shell Oil used to publish basic corrosion rate data in specific fluids. ASM Handbook Volume 13 has basic corrosion rates in specific fluids. Also NACE Store - Corrosion in the Petrochemical Industry.
Corrosion rates will depend on material chemistry, temperature, pressure and composition of fluid. You will not obtain definitive rates for your service. You should talk to plant metallurgists and inspectors to obtain better information.
Many years ago, I attended monthly, informal meetings with Refinery Inspectors in Southern California. The info obtained was invaluable. Network through API and NACE conferences/symposiums as well.