# Washing stainless steel separator from organic residue

In my lab we have a stainless steel separator for liquid products of one of our hi-pressure catalytic testing assembly. It is a steel cylinder with two short pipes and one another short pipe with a valve. The problem is, the separator cannot be disassembled and washed. It accumulated organic residues for unknown time, presumably years (it happened before it moved into our responsibility). Some residues were washed with acetone and other solvents, but we want it much cleaner.

Personally, I would love to threat it repeatedly with a strong oxidizer, but I'm afraid that stainless steel might disagree. Also, heating above 200-300 Celsius unfortunately is out of question.

The residue is from Fischer-Tropsch synthesis, so it probably consists of heavy hydrocarbons and possybly some oxygenates and products of their reactions.

Any suggestions?

• Rather depends on the nature of the organic residues. Strong aq hydroxide soln? Nov 8 '17 at 20:16
• Maybe sth that passivates steel? Nov 8 '17 at 21:47
• @Waylander Added the infor Nov 9 '17 at 4:30

A last choice is chromic acid, $\ce{H2CrO4}$, which in some concentrations does not damage some types of stainless steel. N.B. Chromic acid is toxic, carcinogenic and harmful to the environment. With chlorides, it can produce toxic and volatile chromyl chloride. In high concentration it can cause ignition of materials. Check a material safety data sheet before trying it! Also prepare to dispose of this as hazardous waste. Even if the reference states it is safe for the particular steel in use, try it on an unimportant area... perhaps with some of the organic "gunk", to see if the gunk is removed and the reactor is unharmed.