Abstract
Hydrazine is used as an oxygen scavenger to control corrosion in steam generating systems, despite being a genotoxic carcinogen. The International Conference on Chemicals Management in 2006 adopted the Strategic Approach to International Chemicals Management designed to implement the Johannesburg Plan. The European Union has also implemented the new Regulation on Registration, Evaluation, Authorization, and Restriction of Chemicals to achieve the World Summit on Sustainable Development goals by 2020. Hydrazine is one those chemical that severe restriction has been imposed on and must be replaced by 2020. Alternative chemicals, nontoxic corrosion inhibitors or new oxygen scavenger-free water treatment technologies are preferred. A newly developed amine-based vapor phase corrosion inhibitor was investigated. Electrochemical tests were conducted and showed a significantly lower corrosion rate in boiling water. Short term corrosion tests in boiling water showed a decreased corrosion rate from 5.3 mpy to 1.93 mpy for 50 ppm VCI and 1.32 mpy for 100 ppm VCI addition. Long term corrosion tests in the hot steam generating closed loop system showed a decreased corrosion rate from 8.2-8.9 mpy for the control sample to 0.72-0.74 mpy when washed with 500 ppm VCI solution and subsequently maintained at 100 ppm inhibitor for the test remainder. When Inhibitor added at the beginning of testing resulted in a corrosion rate of 1.09-1.24 mpy (with 100 ppm VCI). XPS analysis showed that the amine-based inhibitor promoted and stabilized a protective (Fe3O4) magnetite oxide on the pipe internals.
