Nashrieh Shimi va Mohandesi Shimi Iran

Nashrieh Shimi va Mohandesi Shimi Iran

Analysis of Dezincification and Galvanic Corrosion in Heat Exchangers of the LPG Unit at Lavan Refinery and Corrosion Control Strategies

Document Type : Research Article

Authors
Rahman Erfani
Mohammad Reza Sarmasti Emami
Department of Chemical Engineering, Mazandaran University of Science and Technology, Mazandaran, I.R.IRAN
Abstract
Various corrosion tests were conducted to investigate the factors contributing to corrosion in the shell-and-tube heat exchangers of the LPG unit at the Lavan Refinery, where seawater is used as the cooling medium to condense butane inside the shell. Two heat exchangers from this unit were selected for detailed examination. Electrochemical noise analysis was employed to study the corrosion products formed on the corroded specimens, while electrochemical impedance spectroscopy (EIS), cyclic polarization, and scanning electron microscopy (SEM) were used to identify the underlying corrosion mechanisms. The results indicated that the brass alloy used in the tubes exhibited satisfactory resistance to both uniform and pitting corrosion; however, the predominant corrosion type was galvanic and selective corrosion occurring at the junctions between the brass tubes and the stainless-steel tube sheets. In addition, erosion–corrosion and corrosion fatigue were clearly detected in these regions. The proposed corrosion control strategies include the application of electrical insulation at joints between dissimilar metals, selection of corrosion-resistant alloys, control of operational conditions, use of protective coatings, filters, and deaeration systems, as well as the implementation of sacrificial anodes. To prevent dezincification, the use of arsenic-containing aluminum brass alloys instead of conventional brass is also recommended.
Keywords
Heat exchanger corrosion
Dezincification
Brass alloy
Electrochemical impedance spectroscopy (EIS)
Cyclic polarization

Subjects

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