Coating for HF Alky Prefrac Charge Drum

[LISAEK]

What coating should I use in a prefract charge drum in an HF alky unit? Contents include C3's, C4's, anhydrous HF at about 90 F. It is carbon steel and estimated long term corrosion rate is low (2 mpy), 3 mpy on acid outlet. Min/max temperature in the 75 - 115 F range. It is nearing end of life on the shell and I would like to prevent more corrosion if possible.

 

[chrysa1975]

Of the non-metallic materials, PTFE is wholly resistant to HF and hydrocarbons,
but its use as a coating for repairs made in situ is virtually impossible because
its polymerisation requires heat treatment under conditions which are hardly
compatible with the facilities normally available when working on plant.
Epoxy coatings do not withstand HF, even when present in traces.
Also consult API RP 751 - Recommended Practice for Safe Operation in HF Acid Alkylation Units for both metallic and non-metallic materials.

 

[rustbuster]

You might consider a flame spray or arc spray application, Alloy C276 if available.

Good Luck

 

[TomEun]

Please find below.

NACE Publication 5A171 (2007 Edition)
NACE Conference Paper 01345/05574/07570
NiDI #10074

 

[LISAEK]

Everyone,

Thank you for your advice. We will not be coating this drum at this time. We will install samples and evaluate during the next unit T/A.