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Self-Assembled Monolayer Mechanism for Corrosion Inhibition of Iron by Imidazolines

Ramachandran, Sunder and Tsai, Bao-Liang and Blanco, Mario and Chen, Huey and Tang, Youngchun and Goddard, William A., III (1996) Self-Assembled Monolayer Mechanism for Corrosion Inhibition of Iron by Imidazolines. Langmuir, 12 (26). pp. 6419-6428. ISSN 0743-7463. doi:10.1021/la960646y.

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Some of the most effective corrosion inhibitors for oil field pipeline applications are the oleic imidazoline (OI) class of molecules. However, the mechanism by which OIs inhibit corrosion is not known. We report atomistic simulations (quantum mechanics and molecular dynamics) designed to elucidate this mechanism. These studies lead to the self-assembled monolayer (SAM) model for corrosion inhibition, which explains the differences in corrosion inhibition efficiency for various OI molecules. The SAM model of OI inhibitors involves the following critical elements:  (i) The function of the OI is to form a self-assembled monolayer on the native oxide surface of iron; this serves a protective role by forming a hydrophobic barrier preventing migration of H_2O, O_2, and electrons to the Fe surface. (ii) The imidazoline head group serves as a sufficiently strong Lewis base to displace H2_O from the Lewis acid sites of the iron oxide surface. (iii) These head groups self-assemble on the surface to form an ordered monolayer on the iron oxide surface. [√3 x √3 for the (001) cleavage surface of α-Fe_2O_3.] (iv) The long hydrophobic tail (e.g., 2-oleic acid) tilts to form a tightly packed hydrophobic monolayer. [For α-Fe_2O_3(001) the tilt angle is about 72° with respect to the surface normal.] (v) This hydrocarbon tail must have a sufficient length to cover the surface. [For α-Fe_2O_3(001) the chain length must be 12 or more carbon atoms.] (vi) The hydrophobic tail and the pendent group (e.g., −CH_2CH_2NH_2) must lead to an octanol/water partition coefficient (log P) below a critical value in order to rapidly form the monolayer. This SAM model should be useful in developing both alternative environmentally benign corrosion inhibitors and higher temperature corrosion inhibitors.

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Goddard, William A., III0000-0003-0097-5716
Additional Information:© 1996 American Chemical Society. Received June 27, 1996. The research was funded by Chevron Petroleum Technology Co. (R. Heming), by DOE-BCTR (D. Boron), and by NSF-GCAG (Grant ASC 92-17368, R. Hildebrand). The facilities of the MSC are also supported by grants from NSF-CHE (Grant 95-22179), Aramco, Asahi Chemical, Chevron Chemical Co., Asahi Glass, Owens-Corning, Hercules, BP Chemical, Chevron Research and Technology Co., Avery-Dennison, and Beckman Institute. Calculations for this project were carried out on the Illinois NSF Supercomputer Center (L. Smarr) and on the JPL Cray (P. Messina).
Funding AgencyGrant Number
Chevron Petroleum Technology Co.UNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
NSFASC 92-17368
NSFCHE 95-22179
Chevron Chemical Co.UNSPECIFIED
Chevron Research and Technology Co.UNSPECIFIED
Caltech Beckman InstituteUNSPECIFIED
Issue or Number:26
Record Number:CaltechAUTHORS:20180719-161618054
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Official Citation:Self-Assembled Monolayer Mechanism for Corrosion Inhibition of Iron by Imidazolines Sunder Ramachandran, Bao-Liang Tsai, Mario Blanco, Huey Chen, Yongchun Tang, and William A. Goddard, III Langmuir 1996 12 (26), 6419-6428 DOI: 10.1021/la960646y
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88040
Deposited By: George Porter
Deposited On:19 Jul 2018 23:26
Last Modified:16 Nov 2021 00:23

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