Chemical Attack on Copper Condenser Coils

Dear Sir/Madam,

Can you please suggest a coating for a copper condensing coil.

We design and build Centrifugal Evaporators for Drug Discovery Pharmaceutical Business's.

Part of our equipment, contains a Condensing Coil for solvent recovery.
Refrigerant is passed through the coil subjecting it to temps of between -40°C and +60°C, allowing us to Condense/freeze solvent vapour onto its outer surface. To prevent too much ice build-up we defrost occasionally, hence the temperature variations.
The condensable Solvents could be HCL, TFA, NH3, ACN, DMSO or H2O.

Our current coil material is FEP coated Copper or Stainless Steel.
We would like to keep with copper, due to good thermal transfer, cost and reduced unit size, but it will require a thin protective coating.

We are currently in the process of testing a Tantalum Coating but would like an alternative.
We could consider a coated Aluminium Coil.
We have investigated spraying the coil but currently rejected it, due to inconsistent coating coverage.

CAN YOU HELP PLEASE

Copper is very high in the electromotive force series and very corrosion resistant, thus any conventional coating of a passive metal will be easily activated and attacked in presence of HCl. Keep trying with the Tantalum. Your other options would be even more expensive (Platinum or Rhodium). G. Marrufo-Mexico