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When to stop pickling?

April 2, 2008

Dear Sirs,
I am a field service manager working in a hydraulic engineering company. Prior to oil flushing of hydraulic carbon steel pipes, we do pickling (circulating method) in order to remove rusts from the inner side. We are doing this process according to our last experiences. Is there any experimental solution for defining the exact time in order to stop pickling. For example taking a sample from the return line ,then titration method or some thing like that. In this way we can prevent any damage or unsatisfied pickling at the right moment. I'm waiting for your help soon!

regards,

Ghasem Shilati
mechanical engineer - TEHRAN, IRAN

Sir:
I presume you are using sulfuric or hydrochloric acid to pickle the inside of your pipes. You need a good inhibitor so that you can "overdue" the time without attacking the base steel. In the magazine Metal Finishing I published an article titled: "Selection and Use of Pickling Acid Inhibitors." I recommend that you read this article.
Regards,

Dr. Thomas H. Cook
Galvanizing Consultant - Hot Springs, South Dakota, USA
April 8, 2008

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