Siderite micro-modification for enhanced corrosion protection

Abstract

Production of oil and gas results in the creation of carbon dioxide (CO2) which when wet is extremely corrosive owing to the speciation of carbonic acid. Severe production losses and safety incidents occur when carbon steel (CS) is used as a pipeline material if corrosion is not properly managed. Currently corrosion inhibitor (CI) chemicals are used to ensure that the material degradation rates are properly controlled; this imposes operational constraints, costs of deployment and environmental issues. In specific conditions, a naturally growing corrosion product known as siderite or iron carbonate (FeCO3) precipitates onto the internal pipe wall providing protection from electrochemical degradation. Many parameters influence the thermodynamics of FeCO3 precipitation which is generally favoured at high values of temperatures, pressure and pH. In this paper, a new approach for corrosion management is presented; micro-modifying the corrosion product. This novel mitigation approach relies on enhancing the crystallisation of FeCO3 and improving its density, protectiveness and mechanical properties. The addition of a silicon-rich nanofiller is shown to augment the growth of FeCO3 at lower pH and temperature without affecting the bulk pH. The hybrid FeCO3 exhibits superior general and localised corrosion properties. The findings herein indicate that it is possible to locally alter the environment in the vicinity of the corroding steel in order to grow a dense and therefore protective FeCO3 film via the incorporation of hybrid organic-inorganic silsesquioxane moieties. The durability and mechanical integrity of the film is also significantly improved.

Engineering of corrosion product-polymer hybrid layers for enhanced CO2 corrosion protection of carbon steel part one: Corrosion study and mechanical property investigation

“…Figure 17 shows the characterised hardness and Young's modulus for FeCO3 and FeCO3 -PAH polymer layers. Despite shorter exposure time in this study, the obtained hardness and Young's modulus of pure FeCO3 layer in the absence of PAH polymer are comparable and consistent with our published mechanical properties of general corrosion products [26]. The hardness of all layers stays independent of administrating PAH polymer showing roughly constant values between 9 to 12 GPa.…”

“…The uninhibited experiment (Figure 4(a)) illustrates that the corrosion rate drops to around 0.1 millimetre/year (mm/yr) after 40 h of exposure. This effect is attributed to the formation of pure FeCO3 layer on the steel surface (as reported in previous studies [5,26]), which reduces the dissolution of the underlying carbon steel by acting as a diffusion barrier and/or blocking active sites on the steel surface.…”

“…For each experimental condition, two square specimens (15 x 15 mm 2 ) were scanned with a total area of 196 mm 2 (14 x 14 mm 2 ) on each specimen. The raw data was analysed in Vision64 software package by applying carefully selected thresholds with distinct pit depths, diameters and areas being quantified, in alignment with previous work [12,26].…”

Substrate Protection with Corrosion Scales: Can We Depend on Iron Carbonate?

“…Alternatively, chemical additives could be employed to further reduce the permeability of the scale, increasing R δ(EIS) S a corr , and so minimize the corrosion rate of the remaining electrochemically active surface. Some effort has already been applied to enhancing the protective properties of FeCO 3 , but further work is required to develop reliable and sustainable solutions. In addition, when in situ chemical intervention is not possible, surface pretreatment prior to service to enhance and retain formed corrosion scales, such as functionally grading the surface by modifying its metallurgy/composition, could be envisaged.…”

Corrosion Control in CO2 Enhanced Oil Recovery From a Perspective of Multiphase Fluids

“…The degree of localized corrosion may be vastly different from the averaged corrosion rate in oil-brine mixed conditions (Choi et al, 1989;Sun et al, 2016a), but this phenomenon and its mechanisms have not been clearly addressed. Some soluble organic compounds in crude oil can also decisively reduce the corrosion rate in a manner like corrosion inhibitors (Efird and Jasinski, 1989;Castillo et al, 2000;Ayello et al, 2013) and they may produce a possible hybrid effect on corrosion products (Mendez et al, 2001;Yang et al, 2014;Taleb et al, 2017).…”