Q. Process of Corrosion in BFW Tank?
The feed to the BFW Tank is hot and will be flashing when it enters the tank. The vapours will be corrosive when the tank is open to atmosphere as water vapour at the top will be saturated with oxygen and high corrosion rate is expected.
In order to minimize the corrosion in BFW Tank it is necessary to keep oxygen excluded from the system and keep the tank pressurized by an inert gas system. Oxygen ingress will cause the BFW to be corrosive to CS, therefore internal tank coating is recommended. It should be noted due to high operating temperature of BFW feed to the tank, a special blend of coating shall be specified to resist in high temperature full immersion service. If the tank is blanketed and the BFW has already been de-oxidized, there is no need for internal tank coating.
The decision for internal coating shall be assessed on a case by case basis and process and corrosion specialists shall be consulted.