ABSTRACT

Adsorption and desorption of a product is an important factor in the assessment of availability requirements for a corrosion inhibitor in a given system. Corrosion inhibitors that have film persistence can allow the safe operation of a corrosive oil and gas system for some time period when corrosion inhibitor injection is interrupted. Successful batch corrosion inhibition occurs when significant corrosion inhibition occurs when a corrosion inhibitor is not present in the bulk phase. This paper describes corrosion inhibitor tests that were carried out at different temperatures and interpreted using Langmuir adsorption and desorption. Studying corrosion inhibitor performance and fitting the behavior with Langmuir adsorption and desorption enables a better determination of safe operating envelopes of a system when corrosion inhibitor injection is interrupted. The tests aid the development of an improved assessment of availability of corrosion inhibitor

INTRODUCTION

An important means to control corrosion in wet flow lines that exhibit carbon dioxide corrosion with slug flow is to ensure availability of an effective corrosion inhibitor.1 To account for times when corrosion inhibitor is not available, a model was developed to account for field corrosion rates, Crf, that is based on the following: actual field corrosion rates on the uninhibited corrosion rate, Cru; the inhibited corrosion rate, Cri; and the fraction of time that the corrosion inhibitor is available in the system, f. This model is provided in Equation 1.1,2

equation

There is often a large variation between actual corrosion inhibitor concentrations seen in the field and recommended corrosion inhibitor concentrations.2 Pump failure, incorrect pump rate settings, inadequate chemical inventory and other problems can restrict the availability of chemicals in the system.2 Managing corrosion inhibitor availability requires a record of inhibitor availability achieved in the system, understanding the events that decrease corrosion inhibitor availability, and a process in place to increase corrosion inhibitor availability.2 The consistency of corrosion inhibitor availability is maintained using a reliable requires chemical injection system and feedback-based dosage control.3

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