E100 ethanol in S235JR storage tank.

[Jay_]

Hello,
We are at the stage of deciding whether to use a stainless steel material or carbon steel material to build our underground horizontal storage tank per EN 12285-1.
As per the code, the usage of carbon steel tank is permitted as long as ethanol doesn't contain bromide or chloride, as well as if it's not acid (ph between 6.5 to 8.5).
but i'm worried about corrosion and especially SCC, it's worth mentioning that the pressure in the tank is only minor and temperature is near ambiant but still...
i have read articles about this issue and it's mainly caused by the desolved oxygen concentration, water concentration, and contaminents.
The decision that i'm unable to decide is whether using a cheap carbon steel tank and risking a higher corrosion rate, or a classy high price stainless steel tank... note that we will paint the internal surface of the carbon steel tank with epoxy phenolic up to probably 300microns.
can anyone please advise?
Am i risking alot with a carbon steel tank in this service?
and if so...purging the tank with N2 will solve the problem??

Detailing is a hobby,

 

[cap1a79]

The most important thing to prevent ethanol stress corrosion cracking is to keep it with "free of oxygen". It has not been reported for the environment under deaerated conditions. (Reference from API RP 571)
Hence, corrosion monitoring like IOW should be established and design of purging system to remove any possibility of oxygen ingress are to be implemented.

Minimizing water content as below 0.1 vol% and applying PWHT (if practical) & coating can help to reduce the risk of the SCC as well.

Refer to API RP 571, 3.28 Ethanol Stress Corrosion Cracking) for more detail.


SiHyoung Lee