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Pickling trouble

Q. We are working with a 10% solution of HCl and water to pickle future fuel lines to new Wartsila engines. Does anybody knows if carbon steel pipe gets damaged after more than 50 hours pickling? Is there a time limit we should be aware of?. Pickling is not an easy work and heating is not recommended as per MSDM of the acid.

Diego Robalino
AEC Ecuador - Ecuador
2005

A. Mr. Robalino,

I would not recommend using hydrochloric acid. I would first degrease the piping with a 2% sodium hydroxide solution at 120-140F for around 4 hours. Use a full flow filter with a 50 micron element and change if necessary. Then rinse with demineralized water and measure the pH of the effluent to determine when all the caustic has been removed. Then circulate a 5-10% citric acid ⇦ this on eBay or Amazon [affil links] solution at 120-140F for 4 hours. Use the full flow filter (with a finer element if desired.) Then rinse with demineralized water and measure the pH and conductivity of the effluent. Stop rinsing when the conductivity of the effluent is within 10 microsiemens/cm3 of the influent rinse water. Then circulate a 1% solution of sodium nitrite for 1 hour at 100F. Drain the piping and dry with nitrogen or clean-dry-air to a pressure dew point of at least -20F. It is very helpful to launch a few drying pigs to purge any standing water before using the compressed gas. Also note, you should take care when measuring the dew point. You should pressurize the system and monitor the dew point for a couple hours. Simply sampling the gas exiting the system will almost certainly give you an erroneous reading. Hope that helps.

Joseph Lockrem
Concord Industrial, Inc. - Indianapolis, Indiana, USA
2005

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Mr. Lockrem.

I truly appreciate your suggestions. I have found here that major pipe suppliers get the pipe and fittings from different vendors all around the world and this makes things even worst.

First pickling went OK with the pipe but all fittings were covered with a stronger lacquer. Some were removed and some not.

We had to grit blast the pipe fittings internally to finally remove this lacquer. Now we are fighting with minor corrosion inside the pipe. After the pickling we started the flushing procedure with diesel and they all got rusted....what a shame !. I found that the neutralizer was not applied properly by my contractor...then back to pickling.

If anyone here is to do this job, I'll strongly recommend SS pipe and fittings, a bit more expensive but it saves you lots of time and efforts (i.e. man hours and equipment).

Best Regards,

Diego Robalino
- Quito, Ecuador
2005