Steps to Developing an Effective Integrated Corrosion Management Program to Minimise Costs & Extend Life

An integrated corrosion management program should be part of the overall asset management and preservation program and should not be treated as/in a separate system. Integrity of assets is a characteristic of sound and safe performance for which it was designed. Other subsets of the overall integrity management program include, e.g. mechanical damage and operating stress.This keynote outlines steps for developing an effective integrated corrosion management program with the aim to minimise costs and to extend life whilst reducing the risk for failure. Cost implications of inadequate corrosion control include both direct and indirect costs, which are correlated. For example, inadequate coatingmaintenance (direct cost) will lead to increased maintenance and repair costs later(indirect costs), which often outweigh the initial costs of simply maintaining the adequate condition of the coatings.The implementation of an integrated corrosion management program, that result in the reduction/elimination of corrosion related damage/deterioration of assets, will notonly assist in compliance with regulatory requirements but also has a direct effect on the assets overall economic performance

Geabacter species enhances pit depth on 304L stainless steel in a medium lacking with electron donor

Geobacter sulfurreducens bacteria increased the open circuit potential of 304L stainless steel by around 320 mV in only a few hours after inoculation. This represents a significant increase in the corrosion risk. In contrast, the oxidation of acetate, which is catalysed by well-established biofilms, shifted the pitting potential towards positive values. In acetate-lacking media, pitting occurred with and without bacteria in the same range of potential values, but the presence of bacteria drastically increased the size of pits. AFM showed pits more than 10 times broader and deeper due to the presence of bacteria. In the absence of acetate, the masking effect due to acetate oxidation disappeared and the full corrosive effect of the biofilm was revealed. This also fully explains why pitting was predominantly observed close to surface areas where bacterial settlement was the densest

Synchrotron infrared microspectroscopy study of the orientation of an organic surfactant on a microscopically rough steel surface

The performance of organic surfactants as corrosion inhibitors is influenced by the mechanism of adsorption and the resulting molecular orientation on the substrate. The molecular orientation of 1-dodecylpyridinium chloride (DPC) deposited on non-corroded 1030 mild steel and after corrosion in a carbon dioxide environment has been investigated using synchrotron infrared microspectroscopy. DPC mitigates the corrosion process by adsorbing at the steel surface and forming a protective layer. Infrared spectra analogous to polarized grazing angle spectra were obtained from a microscopically rough surface using a synchrotron source. The appearance of negative and positive absorption bandsin the spectra, when using synchrotron radiation, is discussed in terms of the optical system used. The presence of the DPC surfactant at the steel surface is shown by the CH2 and CH3 infrared absorption bands of the aliphatic chain of the DPC molecule. The infrared spectra provide direct evidence on the orientation of DPC at the steel substrate. The aliphatic chain of the surfactant is tilted orthogonally, but not perpendicular to the substrate plane. The absence of significant absorption bands characteristic of the pyridinium ring of DPC indicates its orientation parallel to the substrate plane, and an adsorption mechanism involving pi-bonding with the steel. This study demonstrates the applicability of synchrotron infrared microspectroscopy to the investigations of thin organic films on microscopically rough steel surfaces, and can facilitate further investigations of thin films on metallic surfaces and monolayer studies in general

The influence of corrosion inhibitors on hydrate formation temperature along the subsea natural gas pipelines

Pipeline industry annually invests millions of dollar on corrosion inhibitors in order to minimize corrosion׳s implication on flow assurance; however, attention has never been focused on the possibilities of these chemicals to promote hydrate formation along deepwater pipeline which is also a flow assurance problem. Five inhibitors were investigated in this study at different concentrations and pressures in a cryogenic sapphire cell at static condition. The changes in the formation temperature established that all the inhibitors promote hydrate but at different rates while their hydrate formation patterns also differ from one another. Their ability to promote hydrate could be attributed to their hydrogen bonding properties which is required for hydrate formation. Also, the difference in the promotion rate is attributed to their different sizes and structures, active functional groups and affinity for water molecules which determine the type of hydrogen bonding exhibited by each inhibitor while in solution. The structure and size of each inhibitor also affect its electronegativity and ionization energy since the active electrons of some of the inhibitors have direct exposure to the nucleus while for others; the active electrons at the outermost shell have been shielded from direct influence of the attractive force. Furthermore, the active functional groups obeys electronegativity trend of periodic table to determine whether the resulting bond type will be polar ionic, covalent or ionic with some covalent characteristic in nature. Though, all the inhibitors are foamy; dodecylpyridinium chloride (DPC) was however the foamiest. DPC also exhibited its highest promotion ability at 200 ppm and exhibited specific behaviour at 5000 ppm to suggest a change in the hydrate formation rate beyond the Critical Micelles Concentration (CMC). Again, increase in agitation rate prolonged the complete solidification time of the hydrates probably due to the gas solubility. Finally, the feasibility of using this chemical as an additive at high concentrations for natural gas transportation and storage in slurry form was observed due to some exhibited properties, this however requires further investigations

Effect of pretreatment process on scale formation in the re-boiler section of monoethylene glycol regeneration plant

Monoethylene glycol (MEG) regeneration plants often use pretreatment vessels to precipitate divalent cations, such as Fe2+, Ca2+, and Mg2+, in order to avoid or reduce fouling in downstream reboilers and heat exchangers. This pretreatment process operates under alkaline conditions and moderate temperatures (~ 80 °C) to accelerate the formation of low-solubility divalent salts. The objective of the present research was to determine whether the pretreatment process could be minimized, without negatively impacts on the MEG regeneration process from to the formation of scale on the heater bundle in the presence of low concentrations of divalent cations in the rich MEG stream. Scale formation was analyzed under MEG regeneration process conditions using a dynamic scale loop (DSL) test and verification experiments were performed in a MEG regeneration and reclamation pilot plant, both with and without pretreatment conditions. The scaling tendencies of several rich MEG–brine mixtures were evaluated at different pH pretreatment levels and dissolved CO2 concentrations. An evaluation temperature of 180 °C was chosen to match the skin temperature of the reboiler heater bundle during the MEG regeneration process. The experiments of pH 7.24 showed high amounts of precipitation scale within the reboiler due to high remaining concentrations of mineral ions. In addition, small concentrations of calcium and magnesium ions led to the precipitation of calcite, dolomite, and magnesium hydroxide on the reboiler bundle and within associated filtered outputs even when a pretreatment vessel was present. These results were confirmed by the differential pressure build-up and Scanning Electron Microscopy analyses for each experimental condition. Another interesting finding is that pH increased within the reboiler due to CO2 gas boiling off at high operating temperatures, thus contributing to increased alkalinity levels, which in turn promoted scale formation. These results indicate that pretreatment should not be reduced, even with divalent ion concentrations as low as ~ 5 ppm TDS, due to the harsh conditions within the reboiler heater bundle

Removal of monoethylene glycol from wastewater by using Zr-metal organic frameworks

Mono-ethylene glycol (MEG), used in the oil and gas industries as a gas hydrate inhibitor, is a hazardous chemical present in wastewater from those processes. Metal-organic frameworks (MOFs) (modified UiO-66 * and UiO-66-2OH) were used for the effective removal of MEG waste from effluents of distillation columns (MEG recovery units). Batch contact adsorption method was used to study the adsorption behavior toward these types of MOFs. Adsorption experiments showed that these MOFs had very high affinity toward MEG. Significant adsorption capacity was demonstrated on UiO-66-2OH and modified UiO-66 at 1000 mg·g -1 and 800 mg·g -1 respectively. The adsorption kinetics were fitted to a pseudo first-order model. UiO-66-2OH showed a higher adsorption capacity due to the presence of hydroxyl groups in its structure. A Langmuir model gave the best fitting for isotherm of experimental data at pH = 7

Crevice corrosion of duplex stainless steels in the presence of natural marine biofilms

The evaluation of crevice corrosion of high alloy stainless steels used in offshore applications is of major importance as it is one of the most deleterious forms of localized corrosion which may result in sudden marine corrosion failure. The resistance of UNS S31803 duplex stainless steel (DSS) to crevice corrosion in natural seawater was evaluated by immersion and electrochemical tests. Artificially creviced specimens were tested before, during and after immersion in natural seawater under stagnant conditions for up to eight weeks allowing indigenous marine microorganisms to adhere to the alloy surface and form a biofilm. The changes in biofilm community structure and the influence of biofilm on the crevice corrosion of DSS specimens in seawater were investigated at two different exposure times (4 and 8 weeks) using a combination of potentiodynamic and potentiostatic measurements, surface inspection and bacterial community profile analysis by 16S rRNA gene PCR-DGGE and DNA sequencing. Results indicate that our selection approach to evaluate crevice corrosion yields highly reproducible results. Crevice corrosion was observed only in electrochemically polarized specimens that had been exposed to natural seawater containing bacteria. The possible mechanisms involved in the biofilm enhanced crevice corrosion are discussed

Hydrate formation and its influence on natural gas pipeline internal corrosion

Ova studija utvrđuje mogućnost da formiranje hidrata potakne unutarnju koroziju duž plinovoda. Utvrđene vrste korozije, a to su kavitacije, erozija i korozije uzrokovane kemijskim reakcijama, mogu pojedinačno ili zajednički potaknuti rupičastu koroziju i korozijsko raspucavanje uz naprezanje, što je također opasno za plinovod. Ove vrste korozije negativno utječu na ekonomiju, okoliš i ljude tako da gubitci u gospodarstvu dosežu 3 bilijuna US$, ovisno o dužini cijevi, lokaciji, dubini mora, djelovanju valova, klimatskim uvjetima i političkoj situaciji. Na kraju su predložene razne predvidive mjere kako bi se smanjilo stvaranje hidrata.This study establishes the ability of hydrate formation to initiate internal corrosions along natural gas pipelines. The identified corrosion types, which are cavitations, erosion and corrosions by chemical reactions, are capable to individually or collectively initiate pitting and stress cracking corrosions which are also dangerous to gas pipelines. The impacts of these corrosion types are classified to economics, environmental and human loss with the economic loss as much as US$3 trillion depending on the pipe-length, location, sea depth, wave function, climatic conditions and political situations. Various predictive measures to minimize hydrate formations are finally recommended

Measurement of mono ethylene glycol volume fraction at varying ionic strengths and temperatures

The estimation of Mono Ethylene Glycol (MEG) concentration is an essential criterion during the industrial regeneration of MEG to evaluate the efficiency of regeneration process and to control the concentration of MEG reinjected at the wellhead. Although many laboratory methods to determine MEG concentration exist, their application may be costly in terms of the time required to perform sampling and laboratory analysis. For this reason, an alternative method for determination of MEG concentrations has been proposed. This method can be performed on-site utilizing physical properties that can be readily measured using portable measurement devices including refractive index (n D ), electrical conductivity (EC) and total dissolved solids (TDS). The volume fraction (F vm ), n D , EC, and TDS of MEG solutions have been measured at (283.15, 298.15, and 323.15) K, (10–100) vol. %, and at (0, 0.125, 0.25, 0.5, 1.0) M NaCl total volume of solution) ionic strength (IS). The experimental results were then correlated to develop a simplistic model capable of estimating the volume fraction of MEG mixtures at varying ionic strengths. The proposed models will therefore allow a quick and convenient method for the determination of MEG concentrations in the field to quickly identify undesirable changes in produced lean MEG concentration

Filtration–UV irradiation as an option for mitigating the risk of microbiologically influenced corrosion of subsea construction alloys in seawater

The effect of filtration-UV irradiation of seawater on the biofilm activity on several offshore structural alloys was evaluated in a continuous flow system over 90 days. Biofilms ennobled the electrode potential by +400–500 mV within a few days of exposure to raw untreated seawater. Filtration-UV irradiation of the seawater delayed the ennoblement of the steels for up to 40 days and lowered localized corrosion rates in susceptible alloys. Ennobling biofilms were composed of microbial cells, diatoms and extracellular polymeric substances and the bacterial community in biofilms was affected by both the alloy composition and seawater treatment