Role of Asphaltenes in Inhibiting Corrosion and Altering the Wettability of the Steel Surface
Abstract Asphaltenes (heptane insolubles) from a variety of crude oils have been identified previously as contributors to inhibition of internal corrosion of mild steel pipelines. However, the mech...
CO 2 corrosion of mild steel 7
Produced oil and gas are always accompanied by some water and varying amounts of carbon dioxide and in some cases hydrogen sulfide and organic acids. All of these may affect the integrity of mild steel. This has been known for over 100 years, yet internal corrosion of pipelines and other facilities made from mild steel still represents a challenge for the oil and gas industry. Although many corrosion-resistant alloys are able to withstand this type of corrosion, it is a matter of economics: mild steel is still the most cost-effective construction material. The price of failure due to internal corrosion is enormous, both in terms of direct costs, such as repair/replacement costs and lost production, and indirect costs, such as environmental cost and impact on the downstream industries. The following text summarizes the current degree of understanding of CO2 corrosion of mild steel exposed to aqueous environments. Much has been understood about the basic mechanisms, enabling construction of mechanistic prediction models, but many challenges remain, particularly when it comes to effects of corrosion product layers, multiphase flow, additional species, hydrocarbon composition, inhibition, etc. The following sections start out with describing the basic physicochemical phenomena underlying CO2 corrosion and gradually move to more complicated situations, culminating with the list of multifaceted real-life challenges seen in the field.
Carbon Dioxide Elimination from Circle Systems
Ten various circle systems were studied in model experiments. All the experiments were performed using a Waters cannister containing 675–685 g of Durasorbr̀. 300 ml of carbon dioxide were supplied to the system per min. The efficacy of these systems was expressed as the time taken to demonstrate a concentration of 0.6% carbon dioxide in the gas mixture supplied to the patient connection during each respiratory cycle. The carbon dioxide elimination was studied at a gas flow of 2, 4 and 6 1 per min. All the systems showed an effective carbon dioxide elimination for 6 h or more at a flow of 2 1. An increasing efficacy was found with increasing flow, but to a varying extent.