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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conducted using a JEOL JSM-6480LV † and Thermo System Seven detector. † E l e c t r o c h e m i c a l p o l a r i z a t i o n t e s t results for the polarization resistance and corrosion rate measurements are shown in Figures 5 and 6. Both corrosion rate and polarization resistance data showed that VCI-A nano-particles have a 41% lower cor- rosion rate compared with the coarse-par- ticle size. The VIA visual observations are shown in Figure 7. The corrosion rating per NACE TM0208 indicated that the con- trol sample had Grade 0, while the VCI-A coarse-particle rating was Grade 2, and VCI-A nanoparticle rating was Grade 4. The surface condition of samples after VIA tests is shown in Figures 8 and 9. The VCI-A nanoparticle tested samples showed supe- rior corrosion protection during VIA tests. Figures 10 and 11 show significant reduc- tion of the corrosion rate of UNS G10180 steel, continuously exposed (120 days above mist sand corrosion tests, 200 ppm Cl- solu- tion added to sand bed every 72 h) when inhibitor was added to the environment. The adsorption isotherm relationship between surface coverage and tempera- ture for both VCI-A-Coarse and VCI-A- Nano inhibitors on the surface of steel is shown in Figure 12. Adsorption energy was roughly –16,740 J/mol for the nanoparticle- size inhibitor, while adsorption energy was roughly –13,660 J/mol for the coarse-par- ticle-size inhibitor. This energy range is indicative of a strong physical adsorption to the metal surface. 14 However, it can be seen that the interaction of VCI-A-Nano with the steel surface is higher than the coarse inhibitor, leading to better cor - rosion protection. The size effect of this inhibitor appears to be more pronounced at higher temperature than the room tem- perature. X-ray photoelectron spectros- copy (XPS) depth profiling analysis showed ~60 to 80 nm of adsorbed inhibitor on the exposed samples, indicating that the multi- layer BET Model is a more realistic adsorp- tion model than the monolayer Langmuir model for this case. But for the adhesion energy calculation between inhibitor mol- ecules and metal surface, it is appropriate to use the monolayer Langmuir model. Influence of Powder Size of the Vapor Corrosion Inhibitor on Inhibiting Effectiveness FIGURE 7 Photographs of steel samples after VIA tests and their corrosion rating; shows superior performance for VCI-A-nano exposed samples. FIGURE 8 Optical micrographs of steel samples after VIA tests; superior performance is seen for VCI-A-Nano exposed samples. Control VCI-A-Coarse Particles VCI-A-Nano Particles 7 CORTEC SUPPLEMENT TO MP MATERIALS PERFORMANCE JUNE 2017

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