Corrosion of water injection pipelines (WIP) in the oil and gas industry is a major issue involving potential premature life time predictions and unpredicted costs like periodic biocide treatment and pipeline pigging. This paper presents a part of a larger project concerned with improving understanding of the influence of bacterial activity on corrosion, as distinct from abiotic corrosion, in oil and gas transport systems for better management of pipeline systems. Observations are made concerning life time as a function of microbiologically influenced corrosion (MIC) risk and relationships between MIC, bacterial numbers and types, and water quality.

Carbon steel pipelines are widely used for injection of sea and other waters into oil and gas wells so as to increase the rate of recovery, particularly from mature fields. Internal corrosion usually is mild. However, cases of very aggressive channelling corrosion along the bottom of the pipeline have been observed. Practical experience and anecdotal observations have attributed this to microbiologically influenced corrosion even though extensive use is made of preventative measures including biocides, oxygen scavengers, corrosion and scale inhibitors, and pipeline pigging. Interpretation of data and observations for five water injection pipelines, made available by industry, indicate that microbiologically influenced corrosion may play a part in causing channelling corrosion but that the most likely cause is under-deposit corrosion under pipe debris that settles during periods of pipeline shut-downs and low water velocity.

The present study compares corrosion mass loss and pit depth measurements on carbon steel corrosion coupons exposed under similar operating parameters, but with different biological consortia. One set of data were obtained from standard flush disc corrosion coupons used to monitor corrosion rates in a water injection pipeline on the North Sea continental shelf. The coupons were exposed on average for 6 months over 6 years operational time. These data are compared with published corrosion data of coupons exposed in abiotic district hot water systems from several power plants situated in Europe. The exposure time for these coupons was 9 months. Both systems were anoxic and in the same temperature range and are comparable. Observations regarding relationship between MIC and bacterial consortia, bacterial numbers and type, water quality and corrosion products are also made. The corrosion rate of the water injection pipeline is approximately 10 times higher compared with the corrosion rate in the abiotic district hot water system. It is concluded that the increased corrosion on the carbon steel coupons in the early stage is caused by MIC. This is also supported by the chemical and biological information available for the pipelines. The results reported here constitute the first step of an overall study to improve the level of understanding of the bacterial contribution to the total corrosion rates of carbon steel in water injection flowlines. Such understanding is expected to improve management and operational decision-making for practical control of corrosion in the field, by providing predictions of expected life time as a function of control of biotic consortia (e.g. through pigging, and biocide treatments). Further, it will facilitate decisions concerning choice of pipeline construction materials for future design. Copyright 2012, Society of Petroleum Engineers.

A major problem for the management of oil and gas pipelines is corrosion influenced by microorganisms particularly, bacteria. The present study focuses on the influence particularly of the sulfate reducing bacteria on the internal corrosion of water injection pipelines. The research is based on reports from long-term observations of several water injections pipelines from the North Sea continental shelf. Observation data taken into consideration are pigging operation information, composition of corrosion products and their amount, corrosion rates and pipe geometry, identified biological consortia, water chemistry and process parameters. Observations regarding water quality and mitigation methods are made also. The distribution of corrosion including pitting and 'features' along the pipeline as well as the localization of these in relation to the orientation of the surfaces, is considered. This includes different corrosion patterns along the pipeline and the relative severity of six o'clock corrosion. These observations are used to make correlation estimates between severity and location of corrosion and service history and the local environmental conditions, where this information is available. The correlations are used to develop a clearer view of the proportion of biocorrosion contributing to the total corrosion in water injection pipelines. Additionally, an assessment is made of the efficiency of mitigation procedures such as biocide treatments and pigging operations. The paper provides possible explanations for different rates and spatial patterns of corrosion for water injection pipelines. © 2013 by NACE International.

The effect of potential on pit propagation as a function of water chemistry was investigated using artificial pit electrodes. In both 0.01 M HCO 3 - 0.01 M SO 4 2- and 0.01 M HCO 3 - 0.01 M Cl - solutions, pits grew faster at higher applied potentials. However the magnitude of the pitting rate depends on the solution chemistry. A higher pitting rate was observed during pit growth in 0.01 M HCO 3 - 0.01 M SO 4 2- solution compared to 0.01 M HCO 3 - 0.01 M Cl - solution. The chemistry of the water determined the morphology and the molecular identity of corrosion products deposited inside and outside of the pits. Thick and porous layers of malachite and brochantiteposnjakite covered pits in 0.01 M HCO 3 - 0.01 M SO 4 2- solution. In contrast, thin and compact layers of malachite, cuprite and atacamitenantokiteeriochantite covered pits in 0.01 M HCO 3 - 0.01 M Cl - solution. Modeling successfully predicted these corrosion products. Applied potential determined the amount, the structure and the distribution of corrosion products in both experiment and model. However, the effect of potential was more pronounced in 0.01 M HCO 3 - 0.01 M SO 4 2- solution in comparison to 0.01 M HCO 3 - 0.01 M Cl - solution. © 2011 The Electrochemical Society.

The pit propagation behavior of copper (UNS C11000) was investigated from an electrochemical perspective using the artificial pit method. Pit growth was studied systematically in a range of HCO 3 -, SO 4 2- and Cl - containing-waters at various concentrations. Pit propagation was mediated by the nature of the corrosion products formed both inside and over the pit mouth (i.e., cap). Certain water chemistry concentrations such as those high in sulfate were found to promote fast pitting that could be sustained over long times at a fixed applied potential but gradually stifled in all but the lowest concentration solutions. In contrast, Cl - containing waters without sulfate ions resulted in slower pit growth and eventual repassivation. These observations were interpreted through understanding of the identity, amount and porosity of corrosion products formed inside and over pits. These factors controlled their resistive nature as characterized using electrochemical impedance spectroscopy. A finite element model (FEM) was developed which included copper oxidation kinetics, transport by migration and diffusion, Cu(I) and Cu(II) solid corrosion product formation and porosity governed by equilibrium thermodynamics and a saturation index, as well as pit current and depth of penetration. The findings of the modeling were in good agreement with artificial pit experiments. Malachite, bronchantite, cuprite, nantokite and atacamite corrosion products were both observed in experiment and predicted by the model. Stifling and/or repassivation occurred when the resistance of the corrosion product layer became high enough to lower the pit bottom potential and pit current density such as 10 -5 A/cm 2 could be attained with thick and dense layer. The ramifications of these findings towards pit propagation characteristics in potable waters will be discussed with improved insight into the roles of Cl - and SO 4 2- ions. © 2011 Elsevier Ltd. All Rights Reserved.

Zn-5Al and Zn-3Al-2Mg model alloys were cast and heat treated in order to obtain specimens with distinct microstructures and identical chemical compositions. The microstructure was characterised in detail to identify composition, size and distribution of present phases. Mass losses of samples with different microstructures and identical chemical compositions that were subjected to a cyclic corrosion test and a test under non-rinsing conditions differed by a factor of up to two. The mechanism is discussed based on measurements of corrosion stability of individual phases and chemical and phase compositions of corrosion products.

Several cases of ceiling collapses and other failed elements have been reported in indoor swimming pool halls in the last two decades. The collapses were caused by stress corrosion cracking (SCC) of stainless steel fastening elements made of grades UNS S30400, S31600, or similar. It was shown that this phenomenon can occur under specific conditions beneath chloride deposits at temperatures as low as the room temperature. The aim of this study was to assess the application limits of different austenitic and duplex stainless steel grades subject to tensile stress and contaminated with chloride deposits in the atmosphere under non-washing conditions as a function of temperature (20-50 °C), relative humidity (15-70 % RH), and deposit composition. Austenitic stainless steel grades UNS S30400 and S31603 were susceptible to SCC in the presence of magnesium and calcium chlorides at temperatures from 30 °C and at low relative humidity. The tendency to SCC increased with increasing temperature and decreasing relative humidity. The corrosivity of salt at given exposure conditions decreased in the following order CaCl2 > MgCl2 > FeCl3 > NaCl. The corrosivity of chloride deposits was governed by the equilibrium chloride concentration in the surface electrolyte formed as a result of interaction of given chloride salt and air at given relative humidity. Threshold values of the minimum chloride concentration and relative humidity intervals leading to SCC at 30 and 40 °C were established for UNS S30400 and S31603. Duplex stainless steels S32101, S32304, S32205, and S32750 corroded selectively to the maximum depth of 380 μn. Austenitic stainless steels N08904 and S31254 showed no tendency to SCC.

Several cases of ceiling collapses and other failed elements have been reported in indoor swimming pool halls in the last two decades. The collapses were caused by stress corrosion cracking (SCC) of stainless steel fastening elements covered with chloride deposits at temperatures as low as room temperature. The goal of this study was to assess the application limits of different austenitic and austenitic-ferritic (duplex) stainless steels subject to tensile stress and contaminated with chloride deposits in atmospheric non-washing conditions as a function of temperature (20°C to 50°C), relative humidity (15% to 70% RH), and deposit composition. Austenitic stainless steels Type 304 (UNS S30400) and Type 316L (UNS S31603) were susceptible to SCC in the presence of magnesium and calcium chlorides at temperatures of 30°C and higher and at low relative humidity. The tendency to SCC increased with increasing temperature and decreasing relative humidity. The corrosivity of chloride deposits under given exposure conditions decreased in thefollowing order: calcium chloride (CaCl2) > magnesium chloride (MgCl2) > sodium chloride (NaCl). It was governed by the equilibrium chloride concentration in the surface electrolyte formed as a result of interaction of a given salt with water vapor in the air. Threshold values of the minimum chloride concentration and relative humidity intervals leading to SCC were established for Type 304 and Type 316L. Duplex stainless steels S32101 (UNS S32101), 2304 (UNS S32304), 2205 (UNS S32205), and 2507 (UNS S32750) were resistant to SCC but corroded selectively with the maximum depth of 200 μm. Austenitic stainless steels Type 904L (UNS N08904) and Type S31254 (UNS S31254) showed no tendency to SCC.

Zn-5wt.%AI and Zn-3wt.%AI-2wt.%Mg model alloys were cast and heat treated in order to obtain specimens with distinct microstructure and identical chemical composition. The microstructure was characterized in detail using scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX) and x-ray diffraction spectroscopy (XRD) to identify chemical composition, size and distribution of present phases. Mass loss of samples with different microstructure and identical chemical composition subjected to a cyclic corrosion test and a test under non-rinsing conditions differed by a factor of up to two. Some model alloys showed better corrosion performance compared to commercial coatings with similar composition tested in parallel. This indicates that microstructure modification can improve the corrosion performance of industrial zinc alloy coatings. The mechanism is discussed based on measurements of corrosion stability of individual phases, preferential corrosion, composition and stability of corrosion products, dc electrochemical characteristics and infrared absorption spectroscopy (IRRAS) experiments.

The effect of sodium, calcium, and magnesium chlorides deposited on zinc and carbon steel surfaces was studied under atmospheric conditions. The cations strongly affected the corrosion rate of zinc, whereas they had a significantly lower impact on the corrosion of carbon steel. The corrosivity of cations of chloride salts for zinc increased in order of Mg2+ < Ca2+ < Na+. The higher corrosion resistance of zinc treated with calcium and magnesium chlorides was connected to prevention of formation of hydrozincite during zinc exposure in wet air. It was observed that zinc weight loss and the carbonate to simonkolleite ratio in corrosion products were correlating. The principal protective effect of bivalent cations can be seen in the decrease of pH of the surface electrolyte, which was caused by hydrolysis of such cations and subsequent formation of simonkolleite that blocked the cathodic sites.

Modelling and prediction of the copper concentration released from copper plumbing tubes due to corrosion, dissolution, precipitation and other processes has not previously been successful. The model presented here is based on a set of dissolution and precipitation reactions, equilibrium between species in solution and solids, mass balance, kinetic expressions, adsorption isotherms, and surface area coverage by precipitates.The model developed has created two major outputs: first; it is the most conclusive collection of mechanistic considerations to date; and second; reasonable correlations between the model and actual data have been obtained for a broad range of waters. © 2012 Elsevier Ltd.

Copper is the intended canister material for the disposal of spent nuclear fuel in Sweden. At repository depth the groundwater may contain dissolved sulfide. The main goal for this work is to study the tendency for stress corrosion of copper in sulfide solutions and examine the influence of various experimental parameters on stress corrosion. Slow strain rate testing was performed on copper test rods in solutions with 1.0 mM sulfide. The pH was kept near neutral with phosphate or borate buffer. The test matrix included variations in temperature, strain rate, and duration of the tests as well as salt and buffer concentrations. Cross-sections of the specimens after testing were investigated using scanning electron microscope/energy dispersive X-ray spectroscopy detector. Stress–strain curves do not reveal any signs of stress corrosion. However, intergranular corrosion in the shape of crack and pit-like features developed in all tests with 1.0 mM sulfide. The length of the deepest features in all these tests was of the same order of magnitude (10–20 µm). The suggested mechanism proposes that crack-like features originate at the surface of the copper metal from the oxidation of grain boundaries that behave as slightly less noble. © 2023 The Authors. 

A mechanistic model of atmospheric bimetallic corrosion with a simplified empirical approach to the onset of localized corrosion attacks is presented. The model was built for a typical bimetallic sample containing aluminum alloy 1050 and stainless steel 316L sheets. A strategy was developed that allowed the model to be calibrated against the measured galvanic current, geometrical corrosion attack properties, and corrosion products. The pitting-onset simplification sets all pits to be formed at a position near the nobler metal and treated all pits as being of the same shape and size. The position was based on the location of the highest pitting events and the pit attributes on an average of the deepest pits. For 5 h exposure at controlled RH (85%, 91%, and 97%) and salt load (86 μg NaCl/cm2), the model was shown to be promising: both for analysis of local bimetallic corrosion chemistry, such as pH and corrosion products, and for efficient assessment of pitting damage by computing a single largest pit depth. Parametric studies indicated that the pitting-onset approximation deviated the most at the beginning of exposure and when RH was below 91%. © 2023 by the authors.