Materials Performance Supplements


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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followed by 3 h at 22 °C for specimen con- ditioning. After the last 3-h conditioning period, the steel samples were inspected for visible water condensation. Following verification of water condensation on each sample, visual examination of the surface was done and microscopic observation was conducted to determine the corrosion rat- ing for each sample. The corrosion criteria for rating steel specimens consist of Grade 0 through Grade 4. To have a valid test, the control sample must have Grade 0; samples with no inhibitor received the worst grade. The control samples consistently rated a Grade 0 for all VIA tests, therefore validat- ing the test method. Relative humidity and the temperature of each test jar were moni- tored by Sensirion † sensors and data logging software. E l e ctro ch emi cal p o l ari z ation st an - dards for corrosion rate and resistance polarization (Rp/CR) measurements using Gamry Rp/CR † techniques were also used to evaluate the behavior of this inhibitor on the steel samples in 200 ppm chloride solution and to compare overall corrosion behavior of these dif ferent particle size corrosion inhibitors. These electrochem- ical tests were conducted using Gamr y PC4/750 Potentiostat/Galvanostat/ZRA † instrumentation and DC105 † corrosion test software. Samples were polished (1.0 µm), placed in a f lat cell, and tested in deion- ized water solutions containing 200 ppm Cl- and 0.5% and 1.0% VCI. Corrosion tests also were conducted by exposing the CS samples to the misted sand with and without inhibitor to simu- late similar condition of the aboveground storage tanks bottoms. Test duration was 120 d while the sand was misted by 200 ppm chloride solution every 72 h. Corro- sion rates were monitored using electrical resistance probes. Samples were visually inspected and their surface conditions were documented after VIA tests were completed. Photogra- phy, optical microscopy, and scanning elec- tron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDXS) analysis were VAPOR PHASE CORROSION INHIBITORS FIGURE 5 Comparison of corrosion behavior of different particle sizes for VCI-A in 200 ppm chlo- ride solution for UNS G10180 steel. FIGURE 6 Comparison of polarization resistance for different particle sizes of VCI-A in 200 ppm chloride solution for UNS G10180 steel. Experimental Procedure Corrosion behavior of carbon steel (CS) (UNS G10180) samples were studied in two different VCIs with coarse parti- cles (~150 µm, VCI-A-Coarse) and those with nanoparticles (~500 nm, VCI-A-Nano) using NACE International TM0208-2013. 12-13 Figure 4 shows the difference in particle size for these two inhibitors. This laboratory test method evaluates the vapor-inhibiting abil- ity (VIA) of various forms of VCI materials for temporary corrosion protection of fer- rous metal surfaces. The VIA corrosion test method provides for standard conditions in a test jar of water-saturated warm air without the presence of accelerating con- taminants. Water vapor and VCI transport are confirmed and corrosion protection is evaluated in this test method. The VIA tests consist of four steps of sample condi- tioning or saturation for 20 h at 22 °C, cool- ing cycle at 2 °C, and prewarming at 50 °C, † Trade name. 6 JUNE 2017 MATERIALS PERFORMANCE CORTEC SUPPLEMENT TO MP

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