Materials Performance Supplements

CORTEC 2019

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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6 Application of Vapor Phase Corrosion Inhibitors for Contaminated Environments Behzad Bavarian, Lisa r einer, a L ine B. a vanessian, and r eza Yakani, College of Engineering and Computer Science, California State University, Northridge, California, USA Boris a . Miksic, F nace , Cortec Corp., St. Paul, Minnesota, USA Availability and accessibility to clean water for industrial applications such as hydrostatic pressure testing of pipe- lines, vessels, and plumbing distribu- tion systems have been a challenging task, especially when the job sites are in remote locations. These circumstances have forced the use of contaminated water containing, for example, large amounts of chloride. Hydrostatic test- ing of metallic equipment is an import- ant method for quality control of parts, after production and during use. When contaminated water is used in these tests, corrosion of the metallic compo- nents of the system during and after testing become a major concern; there- fore, application of an inhibiting system is required. Vapor-phase corrosion in- hibitors (VCIs) can be added to water in small concentrations to prevent corro- sion during testing, or wet storage and after testing. These inhibitors are to pre- vent corrosion of metallic components in three phases: within the solution, at the water line, and above the water line. Three commercially available corrosion inhibitors were evaluated in this study to optimize the best combination of in- hibitors to minimize the corrosion of these multi-metallic component sys- tems. Laboratory studies presented in this article show the effectiveness of VCI products in both fresh and salt wa- ter applications. Results confirmed the effectiveness of VCI products in various water chemistries including fresh and salt water. The average corrosion rate dropped from ~10 mpy for salt solution to less than 1 to 1.6 mpy when various inhibitors were added. However, the effectiveness of these inhibitors is re- markable in the fresh water (less than 0.4 mpy). Exposure of the steel samples to these inhibitors did not show any loss in mechanical properties. Both strength and ductility of the low carbon steel samples were maintained. Ad- sorption energy for these inhibitors was about –21,520 to –24,970 J/mol, indicat- ing a strong physisorption mechanism. The application of an inhibitor in any water system requires compliance with the Clean Water Act and the National Pollutant Discharge Elimination System (NPDES). The three corrosion inhibitors investigated were water-based, bio- based, environmentally friendly, and can be effective replacements for toxic nitrite, chromate or hydrazine-based in- hibitors and satisfy all the required envi- ronmental compliance regulations. Hydrostatic pressure testing of metallic equipm ent such as pip es, vessel s, and valves is an important method for qual- ity control of parts, after production and during use in order to demonstrate the strength and integrity of the systems. 1 This test is a key part of ensuring that they are fit for purpose depending on factors such as contact time, chemicals used, oxygen, and bacteria. Water is the most common media to be used in this test; however, cor- rosion of the metal during and after testing is a concern because the water is typically left in pipelines from a couple of days to months. The challenge is that hydrostatic test water is corrosive, and disposal of the water is costly. Hydrostatic test water con- tains micro-organisms, oxygen, and sedi- ment that are known to accelerate corro- sion progression. Also, because of the large volume of water used, treatment can be very expensive. In some cases, equipment that has gone through a hydrostatic test will also be stored for future use or shipped lon g di stances. Thi s stora ge may take place while water is still inside the equip- ment (wet storage) or even after draining. 2-4 Therefore, a pipeline undergoing a hydro- static test may become quite vulnerable to general corrosion, crevice and pitting corrosion, stress corrosion cracking, dif- ferential aeration corrosion, or microbially induced corrosion. 2 Corrosion caused by VAPOR PHASE CORROSION INHIBITORS 6 JUNE 2019 MATERIALS PERFORMANCE CORTEC SUPPLEMENT TO MP

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