Corrosion carbon dioxide

To prepare gas for evacuation it is necessary to separate the gas and liquid phases and extract or inhibit any components in the gas which are likely to cause pipeline corrosion or blockage. Components which can cause difficulties are water vapour (corrosion, hydrates), heavy hydrocarbons (2-phase flow or wax deposition in pipelines), and contaminants such as carbon dioxide (corrosion) and hydrogen sulphide (corrosion, toxicity). In the case of associated gas, if there is no gas market, gas may have to be flared or re-injected. If significant volumes of associated gas are available it may be worthwhile to extract natural gas liquids (NGLs) before flaring or reinjection. Gas may also have to be treated for gas lifting or for use as a fuel. 

Cyclohexylamine is miscible with water, with which it forms an azeotrope (55.8% H2O) at 96.4°C, making it especially suitable for low pressure steam systems in which it acts as a protective film-former in addition to being a neutralizing amine. Nearly two-thirds of 1989 U.S. production of 5000 —6000 t/yr cyclohexylamine serviced this appHcation (69). Carbon dioxide corrosion is inhibited by deposition of nonwettable film on metal (70). In high pressure systems CHA is chemically more stable than morpholine [110-91-8] (71). A primary amine, CHA does not directiy generate nitrosamine upon nitrite exposure as does morpholine. CHA is used for corrosion inhibitor radiator alcohol solutions, also in paper- and metal-coating industries for moisture and oxidation protection. 

Carbon dioxide dissolves in water to form a weak acid (carbonic acid), which reduces the pH of the solution and, consequently, increases its corrosivity. Corrosion caused by carbon dioxide is generally referred to as sweet corrosion, and results in pitting. The mechanism of carbon dioxide corrosion is as follows [197,198] ... 

Carbon dioxide corrosion can be controlled by the use of caustic soda and lime and the addition of various inhibitors. Film-forming amine inhibitors are used to reduce the corrosion rates. The control measures will be discussed later. 

R. Bruckdorfer. Carbon dioxide corrosion resistance in cements. In Proceedings Volume, volume 2, pages 517-525.36th Annu Cim Petrol Soc Can Soc Petrol Geol Tech Mtg (Edmonton, Canada, 6/2-6/5), 1985. 

C.S. Fang, J.D. Garber, P. Perkins, J.R. Reinhardt, Computer Model of a Gas Condensate Well Containing Carbon Dioxide , CORROSION/89 , Paper No. 465, NACE, Houston, Texas, 1989. 

The data of Table 10.26 can now be interpreted in terms of mass transport. Above a critical flow velocity, which depends on pipe diameter, the rate of mass transport becomes sufficiently fast to carry away dissolved corrosion products without forming a salt film. In other words, their surface concentration remains below saturation. Under these conditions scales that are formed by precipitation of corrosion products at lower flow velocity can not exist and the corrosion rate therefore will be higher. An example in case is carbon dioxide corrosion of carbon steel that occurs in fluids containing... 

Crolet, J.-L. amd Bonis, M. R., pH Measurements in Aqueous CO2 Solutions under High Temperature and Pressure, Carbon Dioxide Corrosion in Oil and Gas Production, L. E. Newton et al, Eds, National Association of Corrosion Engineers, Houston, TX, 1984, pp. 178-184. 

The chemistry of carbon dioxide corrosion in the oil and gas industry is well-known and will not be discussed here. There are extensive research papers available on that subject [see, for example, Nesic (1995)]. The corrosion rate increases with carbon dioxide partial pressure, due to increased dissolution of the gas into the aque-... 

Designing tests to effectively evaluate the effects of corrosion inhibitors on localized corrosion is a highly challenging task. This is illustrated by a practical case of developing a test for evaluating the performance of underdeposit carbon dioxide corrosion inhibitors imder simulated oil pipeline conditions. Corrosion... 

B. Kinsella, Y. J. Tan and S. Bailey, Electrochemical impedance spectroscopy and surface characterization techniques to study carbon dioxide corrosion product scales . Corrosion, 54,835 (1998). 

The corrosion of steel by carbon dioxide and other dissolved gases has been studied on a laboratory scale by Watkins and Kincheloe (1958) and Watkins and Wright (1953). These investigators found that the presence of oxygen greatly accelerates the rate of corrosion by carbon dioxide, while hydrogen sulfide in small quantities inhibits carbon dioxide corrosion. G>mparative data taken from their corrosion curves are presented in Table 6-9. 

Vapor-phase inhibitors (VPIs), also called volatile corrosion inhibitors (VCIs), are compounds which are transported in a closed system to the site of corrosion by volatilization from a source. In boilers, volatile basic compounds such as morpholine or octadecylamine are transported with steam to prevent corrosion in condenser tubes by neutralizing acidic carbon dioxide. Corrosion inhibitor compounds vaporize from the paper or film. They are attracted to the charged surface of the metal by virtue of their polar orientation. 

M. Foss, E. Gulbrandsen, J. Sjoblom 2008. Alteration of wettability of corroding carbon steel surface by carbon dioxide corrosion inhibitors - Effect on carbon dioxide corrosion rate and contact angle. Corrosion 64 (12), 905-919. 

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