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CORROSION PROTECTION OF COPPER IN OILY MEDIA: MICROSCOPIC MECHANISMS

Biswas, Avidipto
http://rave.ohiolink.edu/etdc/view?acc_num=case1364487333

Abstract Details

2013, Doctor of Philosophy, Case Western Reserve University, Materials Science and Engineering.
Tolyltriazole (TTAH) is an extensively used industrial-grade corrosion inhibitor (CI) for Cu. This PhD project developed an understanding on the microscopic mechanisms for the TTAH adsorption on Cu, and the effective protection against sulfide-attack in oily medium analogous to automotive lubricants. XPS and ToF-SIMS characterization were carried out on TTAH adsorption films formed on pristine Cu surfaces immersed in 0.01 wt. % TTAH oil solution at room temperature for immersion times ranging from 1 s to 0.6 Ms. Instantaneous complete coverage of the Cu surface by TTAH is revealed by ToF-SIMS. In Tougaard analysis of XPS spectra, the adsorption film morphology is best described by a uniform-layer model assuming a film thickness of 2.5 nm after 86.4 Ks. Depth-profiling in ToF-SIMS and ARXPS provide evidence for two distinct adsorption configurations for TTAH on Cu – polymerized layer, and monomer layer. TTAH adsorption is found to take place on Cu2O. Studying the time-dependent evolution of the surface film suggests a kinetics-controlled mechanism involving two competing reactions: oxidation of Cu to Cu2O, and TTAH-Cu complex formation. The TTAH-Cu complex formation proceeds at the cost of Cu2O. The structure and the chemical-composition of the surface film fluctuate with reaction time. Studying the corrosion of Cu in sulfide solution at 80C in the absence of TTAH suggests that the oxidation of Cu to Cu2O is kinetically favored over Cu corrosion by sulfide attack. The incubation time for the sulfide-attack decreases with increasing S concentration. Two distinct sulfide corrosion products are identified – Cu2SO4, forming at the oxide interface, and Cu2S, forming atop. The presence of TTAH significantly impedes the extent of sulfide-attack. At 80C, the TTAH adsorption film is substantially thicker than that of room temperature. This suggests that the rate-determining step for the formation of the adsorption film is the outward diffusion of Cu from the substrate. At this temperature, the TTAH adsorption film also reveals a substantially lower degree of polymerization. In the presence of TTAH, both oxidation and sulfide related corrosion of Cu occur underneath the CI adsorption film. The TTAH adsorption film preferentially allows the transport of O through it, leading to the formation of a substantial Cu2O under-layer, while blocking the sulfide radicals. The TTAH adsorption film-forming mechanism proposed in this work explains a number of observations for TTAH- and BTAH-Cu systems reported in the literature, both in oily and aqueous media. The protection of the Cu surface against sulfide attack is attributed to the formation of a physical barrier by TTAH-Cu complex rather than blocking of active sites on the surface. Hence, future research should be focused on finding CI capable of forming better packed Cu-complex structures.
Frank Ernst (Advisor)
Arthur Heuer (Committee Member)
Jay Mann (Committee Member)
Jim McGuffin-Cawley (Committee Member)
174 p.
Automotive Materials; Engineering; Materials Science; Metallurgy
Copper Corrosion-Inhibition; Oily-Media Sulfide-Corrosion of Cu; XPS; ToF-SIMS; Cu-Surface Spectrometry; Corrosion Inhibition Microscopic-Mechanism; Tolyltriazole Corrosion-Inhibitor Adsorption on Cu; Temporal Evolution of Tolytriazole/Cu Adsorption-Film

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Citations

  • Biswas, A. (2013). CORROSION PROTECTION OF COPPER IN OILY MEDIA: MICROSCOPIC MECHANISMS [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1364487333

    APA Style (7th edition)

  • Biswas, Avidipto. CORROSION PROTECTION OF COPPER IN OILY MEDIA: MICROSCOPIC MECHANISMS. 2013. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1364487333.

    MLA Style (8th edition)

  • Biswas, Avidipto. "CORROSION PROTECTION OF COPPER IN OILY MEDIA: MICROSCOPIC MECHANISMS." Doctoral dissertation, Case Western Reserve University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1364487333

    Chicago Manual of Style (17th edition)

case1364487333
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This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.