Corrosion and its mitigation remain a critical challenge in the energy and chemical sectors, particularly in refinery applications where acid dewpoint corrosion poses a serious risk to refinery asset integrity. Where carbon steel is used as the material of construction for oil refinery equipment, corrosion inhibitors are often deployed as a mitigation strategy to protect hardware from corrosive attack. When formulating inhibitors for specific applications, such as corrosion in systems with condensing acid vapours, the selected active components should have physical properties that aid in their formulation and delivery, such as solubility in a particular solvent, advantageous partitioning coefficients for relevant phases, and vapour pressure for volatile components. However, empirical evaluation of these physical properties (and others) can be difficult due to complexity of the requisite test method, excessive cost and time investment, and the safety and risk aspects of the chemicals in question. We present an application of a quantum chemistry computational workflow to generate physical property data for screening of corrosion inhibitor chemistries, specifically for systems where corrosion is occurring in the vapour phase and inhibitor chemistries shown to mitigate corrosion in hydrochloric acid. The workflow uses extended tight binding (xTB) calculations to pre-optimise molecular structures, before conformer-rotamer ensemble sampling with the CREST program and energetic sorting with CENSO to enable efficient exploration of the molecular conformational space. The lowest energy molecular conformers were used to generate application-relevant physical properties using the COSMOtherm software package, allowing identification of chemistries suitable for the application in question. The list of candidate chemistries for the study was identified from a comprehensive review paper on corrosion inhibitors for steels in acidic media. The implications of our work are twofold: first, it shows the value of the xTB/CREST/CENSO workflow in conjunction with COSMOtherm as a rapid and cost-effective method for generating application-specific physical properties to aid in selection of chemistries for mitigating acidic corrosion in the vapour phase; second, it provides a computational foundation for inhibitor formulation design where formulations can be tailored for specific and demanding applications, with chemistries ranked by application-relevant physical properties calculated using quantum chemistry such as vapour pressure and partitioning coefficients. Screening by these computational physical properties would allow more focussed formulation design in areas such as top-of-line corrosion and corrosion in multiphase systems in upstream oil and gas production.
