Daniel Ejdeholm, Karin Jacobson
Papers # 2014 Chicago
Since decades, non-metallics have been the preferred choice of material to be used in the process equipment of pickling plants to cope with the metal-corrosive environments. The present experience regarding the corrosion performance of different plastic materials in various pickling applications and elsewhere has mostly been gained by full-scale use of the process components under actual service. This study is a part of the project “Cost effective and reliable use of plastic and other non-metallics in pickling plants – Corrosion resistance and long-term performance” carried out at Swerea KIMAB, whose ultimate goal is to improve service reliability of polymeric materials when used in pickling environment. The overall aim for this study has been to reach a deeper understanding of the corrosion behaviour of polypropylene in mixed acid (HF+ HNO3). Mixed acid is used for the pickling of stainless steel and due to reasonable price/performance polypropylene is one of the most commonly used pipe materials for this application.
In our study it was found that PPH-β and PPB has a better resistance to the mixed acid environment both regarding corrosion rate and retained impact strength compared to PPH-α and PPR. The study included both pipes that had been in service and pipes that had been exposed to accelerated testing in the laboratory.
There are great potentials in economical savings as well as in safety and reliability for process equipment in pickling plants when having relevant material data to rely on when choosing pipe material.