Formation Of Corrosion Scale Research Articles

Study on deposit formation model in sulfide-containing natural gas environment

The breathing pipe of a produced water storage tank in a sulfide-containing natural gas station is prone to deposit formation, which leads to pipeline blockage. In this study, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses of the deposit in breathing pipe show that the deposit is composed of elemental sulfur and corrosion scales of ferrous polysulfide and ferrous sulfate. Existing deposit formation prediction models cannot predict the formation of elemental sulfur and corrosion scales in sulfide-containing environments. Herein, based on thermodynamic models of elemental sulfur and corrosion scale formation, deposit formation models of elemental sulfur, ferrous polysulfide, and ferrous sulfate scale formation are established. It is found that deposition of elemental sulfur and ferrous polysulfide increases with decreasing temperature of the breathing tube. Corrosion of pipe in the precipitating corrosive water leads to higher activity of left[{mathrm{Fe}}^{2+}right] on the inner wall of the pipe carried by the sulfide-containing natural gas. Consequently, ferrous polysulfide and ferrous sulfate are easily deposited when the activity products of ferrous, sulfide, and sulfate ions are higher than the thermodynamic solubility product constant. The aforementioned prediction models are applied to predict the deposition of ferrous polysulfide, ferrous sulfate corrosion scale, and elemental sulfur using the chemical composition data of gas and precipitating water in the breathing pipe of the produced water tank of TB101-X1 well. The prediction results of the models are consistent with those of actual chemical composition analysis, which verifies the accuracy and reliability of the models.

Insights into the perforation of the L360M pipeline in the liquefied natural gas transmission process

The cause of the failure of a liquefied natural gas transmission pipeline that has experienced internal corrosion during the water injection, idle and transmission processes, is fully investigated in this work. There are two significant features of pipeline failure, namely, the perforated location at the 6o’clock position and under scales deposit. Hence, the 2# leakage point and corrosion scale character were investigated in this research. The perforation of pipeline is attributed to three consecutive stages: (a)corrosion scale formation and pitting initiated, (b) the thickening of the scales and pitting propagation, and (c) the deposit of scales and pitting growth. Among of that, the deposited scales accelerate the pits growth during the LNG transmission process. Meanwhile, the premise cause of the failure was the scales deposit and pits initiation, pits propagation caused in water injection and idle processes.

Review on corrosion and corrosion scale formation upon unlined cast iron pipes in drinking water distribution systems

The qualified finished water from water treatment plants (WTPs) may become discolored and deteriorated during transportation in drinking water distribution systems (DWDSs), which affected tap water quality seriously. This water stability problem often occurs due to pipe corrosion and the destabilization of corrosion scales. This paper provides a comprehensive review of pipe corrosion in DWDSs, including corrosion process, corrosion scale formation, influencing factors and monitoring technologies utilized in DWDSs. In terms of corrosion process, corrosion occurrence, development mechanisms, currently applied assays, and indices used to determine the corrosion possibility are summarized, as well as the chemical and bacterial influences. In terms of scale formation, explanations for the nature of corrosion and scale formation mechanisms are discussed and its typical multilayered structure is illustrated. Furthermore, the influences of water quality and microbial activity on scale transformation are comprehensively discussed. Corrosion-related bacteria at the genus level and their associated corrosion mechanism are also summarized. This review helps deepen the current understanding of pipe corrosion and scale formation in DWDSs, providing guidance for water supply utilities to ensure effective measures to maintain water quality stability and guarantee drinking water safety.

Influence of drinking water quality on the formation of corrosion scales in lead-bearing drinking water distribution systems

Lead in drinking water occurs in drinking water distribution systems (DWDS) where lead pipes are used as service lines. Using data gathered from 4 different Canadian cities, we link drinking water quality to composition of corrosion scales obtained on exhumed lead pipes servicing those municipalities. The data presented encompasses a 10-year span and a detailed layer profile analysis of the solids present in lead bearing service lines; where different layers within the corrosion scale formed inside lead pipes are identified and thoroughly characterized. The results obtained clearly show that the corrosion layers in direct contact with drinking water are rich in lead oxides phases and aluminosilicates. In contrast, lead carbonates are the main phases present on corrosion scales in direct contact with the metallic lead pipe. This heterogeneity on phase distribution is correlated to the radial distance from the corrosion scales to the water/solid interphase and water quality servicing those municipalities. Statistical analysis suggests that dissolved Al, Mn, Cu, Ni, and As accumulate on the corrosion scales with preferential accumulation of specific elements heavily dependent on distinct municipality water quality.

Microbiologically influenced corrosion of welded AISI 304 stainless steel pipe in well water

This work analyzes the premature corrosion failure of a welded AISI 304 stainless steel (SS) pipe network in well water (WW) for 6 months. Laboratory tests were performed to analyze the corrosion behavior and to identify and distinguish the genera of bacteria. Pipe specimens were analyzed using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, open circuit potential, cyclic potentiodynamic polarization, and electrochemical impedance spectroscopy. Physicochemical properties of WW in the AISI 304 SS pipe presented a positive Langelier saturation index, indicating the formation of corrosion scales. In welded 304 austenitic SS, the chromium depletion both in HAZ and in weld-metal leads to preferential anodic dissolution. The biofilm electrochemical activity produces oxygen concentration cells and the acid metabolic products induce preferential MIC, thus leading to pit formation on the HAZ of the weld. Biodiversity analysis of bacteria by next generation sequencing was carried out in corroded AISI 304 SS pipes and different genera of bacteria were identified.

Effect of extremely aggressive environment on the nature of corrosion scales of HP-13Cr stainless steel

The nature of corrosion scales formed on HP-13Cr stainless steel (HP-13Cr SS) in the extremely aggressive environment was investigated by means of microstructure characterization and high-temperature-high-pressure electrochemical measurements. The results of these studies indicated that the precipitation of Cr(OH)3 is the dominating factor affecting on the formation of corrosion scales, and its effect can be categorized based on two compromising aspects. On the one hand, Cr(OH)3 precipitation contributed to the increase of scales thickness. On the other hand, it inhibited the precipitation of FeCO3 due to the hydrolysis of Cr3+. Because of these reasons, the corrosion scales undergo significant microstructural changes, i.e., from monolayer (95 °C/2.8 MPa) to bilayer (120 °C/3.2 MPa and 150 °C/3.6 MPa), then to single layer (180 °C/3.8 MPa). Therefore, the corrosion-resistance performance of corrosion scales decreased with increasing temperature and CO2 pressure, wherein the decreasing pitting potential and repassivation potential accompanied with the increasing density and diffusivity of acceptor in the scales.

Modeling and experimental studies on CO2-H2S corrosion of API carbon steels under high-pressure

This article presents results of a corrosion study conducted to investigate performance of API carbon steels (T95, C110 and Q125) in high-pressure sour environment. This study is aimed to shows the impact of H2S concentration on corrosion of these materials and developed a mathematical model to predict corrosion rate.Corrosion tests were carried out in 2% NaCl solution saturated with mixed gas containing H2S, CO2 and CH4. H2S concentration was varied from 0 to 150 ppm (mole basis) while maintaining the concentrations of CH4 and CO2 approximately at 50%. Test pressure and temperature were 41.37 MPa and 38 °C. Weight loss (WL) technique was used to measure corrosion rate after one-week exposure.Results show that addition of small amount of H2S (less than 10 ppm) promotes CO2 corrosion, regardless of the type of steel. Q125 carbon steel demonstrated higher corrosion resistance than other tested steels, especially in absence of H2S. Various scattered and non-protective corrosion scales were formed on tested specimen surface. A very dense compact scale was formed on C110 carbon steel at 50 ppm H2S, resulting in considerable reduction in corrosion rate.To identify the existence of visually undetectable localized corrosion, the specimen Load Carrying Capacity (LCC) was measured using a tensile strength measuring apparatus. Reduction in total Load Carrying Capacity (ΔLCCT) and reduction in Load Carrying Capacity due to uniform corrosion (ΔLCCuc) were determined and compared to detect localized corrosion. When tests were conducted with C110 and Q125 carbon steels at H2S concentration of 50 ppm, ΔLCCT and ΔLCCuc showed significant difference indicating the occurrence of some form of localized corrosion along with uniform corrosion.A corrosion model, which is valid for high-pressure has been developed considering homogenous chemical reactions, mass transfer process and electrochemical reactions. Model predictions demonstrate reasonable agreement with measurements with maximum discrepancy of 25%, mostly resulting from formation of corrosion scale.

Effects of Flow on Scales Formation in a CO2 Saturated Brine Environment

A significant amount of literature exists demonstrating the effect of CO2 on corrosion scale formation under non-flow conditions. However, literature available on the effects of flow on the nature and protectivity of corrosion scale has many contradictions. This work demonstrates the effects of flow on the nature of corrosion scale for five different oil-field grade steels of varying chemistry (in terms of micro-alloying) and microstructures (ferritic /pearlitic and martensitic), in a CO2 saturated (~1bar) brine (0.5 M NaCl) environment under three different pH (4.2, 6.3 and 6.8) conditions and different temperatures. Flow was introduced using a rotating disk electrode (RDE). The effect of flow was electrochemically characterized by chronoamperometry measurements at various temperatures and pH values. The morphology of the formed scale at the steel surface was analyzed by SEM. Similar to our previous findings, high pH (≥ 6.3) and high temperature (~80 oC) found to favor the formation of protective crystalline scale. Within the preferred conditions (higher pH and temp.) of protective scale formation, higher flow rates in general caused the formation of a protective scale to be sluggish. At lower pH and temperatures, the non-protective scale showed their degree of non-protectivity by allowing higher current density passing through them. Higher Cr content in the steels led to higher degree of protectivity presumably by inducing a higher degree of supersaturation in the local environment which facilitated the formation of a protective crystalline scale. Also, higher Mo content appeared to make the formation of protective crystalline scale relatively sluggish.

Effects of Flow on Protective Scales Formation in a CO2 Saturated Brine Environment

A significant amount of literature exists demonstrating the effect of CO2 on corrosion scale formation under non-flow conditions and its pH and temperature dependent protectivity. However, little information is available on the effects of flow on the nature and protectivity of corrosion scale. This work demonstrates the effects of flow on 4 different oil-field grade steels of varying chemistry (in terms of micro-alloying) and microstructures (ferritic /pearlitic and martensitic), in a CO2 saturated (1bar) brine (0.5 M NaCl) environment under conditions (pH = 6.3 and temperature = 80 oC) which generate a significantly compact and protective scale under non-flow conditions. Flow was introduced in the range of 0 - 3000 RPM via a rotating disk electrode (RDE) type arrangement which has been customized to comply with the needs of the experiment. The effect of flow was electrochemically characterized by potentiostatic current density (id ) vs time (t) measurement where Pt and Ag/AgCl were used as counter electrode and reference electrode respectively. Higher RPM (≥1000) indicated distinct characteristics compared to the lower RPMs (≤100) with a transition of i vs. t behavior observed around 500 RPM. Higher RPMs seemed to modulate the mechanism of the nucleation stage of scale formation and induce a relatively sluggish formation of protective scale by delaying the crystal growth process. Two plain carbon steels, J55 (ferritic /pearlitic) and L80 (Martensitic), did not show any qualitative difference in their i vs. t characteristics as function of flow. However, L80 steel required a longer time for crystal growth and achieving a similar degree of protection through scale formation compared to J55. 1 wt.% Cr micro-alloyed steels showed a lower current density compared to the plain carbon steels at the very early stage of scale formation; however the eventual protectivity of the scales formed on the plain carbon steels appeared to be much better on the basis of i vs t characteristics. Further characterizations of the scales in terms of phase identification, morphology and thickness by XRD, SEM and profilometry are in progress. Figure 1

Stainless steel corrosion scale formed in reclaimed water: Characteristics, model for scale growth and metal element release

Stainless steels generally have extremely good corrosion resistance, but are still susceptible to pitting corrosion. As a result, corrosion scales can form on the surface of stainless steel after extended exposure to aggressive aqueous environments. Corrosion scales play an important role in affecting water quality. These research results showed that interior regions of stainless steel corrosion scales have a high percentage of chromium phases. We reveal the morphology, micro-structure and physicochemical characteristics of stainless steel corrosion scales. Stainless steel corrosion scale is identified as a podiform chromite deposit according to these characteristics, which is unlike deposit formed during iron corrosion. A conceptual model to explain the formation and growth of stainless steel corrosion scale is proposed based on its composition and structure. The scale growth process involves pitting corrosion on the stainless steel surface and the consecutive generation and homogeneous deposition of corrosion products, which is governed by a series of chemical and electrochemical reactions. This model shows the role of corrosion scales in the mechanism of iron and chromium release from pitting corroded stainless steel materials. The formation of corrosion scale is strongly related to water quality parameters. The presence of HClO results in higher ferric content inside the scales. Cl− and SO42− ions in reclaimed water play an important role in corrosion pitting of stainless steel and promote the formation of scales.

Reaction and transport in wellbore interfaces under CO2 storage conditions: Experiments simulating debonded cement–casing interfaces

Debonding-defects at the interfaces between wellbore casing and cement are widely recognized as providing potential pathways for CO2 escape from geological storage systems. This study addresses how chemical reaction between CO2, cement and steel may affect the transport properties of such defects under near-static conditions, representative for early stages in leakage pathway development, prior to formation of a fully connected defect network. Debonded cement–steel interfaces were simulated by constructing composite samples, containing a spacer-imposed gap. These were subjected to batch reaction with CO2 and a variety of aqueous solutions, in multiple consecutive runs (6×5 days plus 1×42 days). The experiments were conducted at 80°C and 14MPa applied CO2-pressure. Permeability was measured after each run. Two ranges in gap-width were investigated, namely 50–120μm (SA-samples) and 270–350μm (LA-samples). Reaction-induced permeability changes were less than 1 order in all samples, and occurred in the early stage of testing. SEM study showed Fe-carbonate scale films developed on both cement and steel. Calcium carbonates precipitated on the cement beneath the gap-spacers, where corrosion scale did not form. We infer that corrosion scale formation on the cement wall inhibited both CaCO3 precipitation and healing effects previously observed in fractured cement.

Effect of the carbon dioxide pressure on the electrochemical behavior of 3Cr low alloyed steel at high temperature

Electrochemical corrosion behavior of 3Cr steel in CO2-containing solution at a high temperature was investigated by various electrochemical measurements and analysis as well as thermodynamic calculations of ionic concentrations and equilibrium electrode potentials. A conceptual model was developed to illustrate the electrochemical corrosion mechanism of 3Cr steel in the CO2-containing sodium chloride solution. Comparing the corrosion potentials of 3Cr steel in the test solution under different CO2 pressures with the conceptual model, it is found that anodic reactions of the 3Cr steel contain a direct dissolution of Fe, and the formation of corrosion scales, FeCO3 and Cr(OH)3, by Fe+HCO3−=FeCO3+H++2e and Cr+3OH−=Cr(OH)3. With the CO2 pressure increasing, the corrosion potential has a positive shift. It indicates that the CO2 pressure has a greater effect on the cathodic reaction than that of anodic reaction. And the corrosion current has positive linear relationship with the increase of CO2 pressure. It is attributed to the concentration increasing of the reactants of the cathodic reaction. According to analysis of the electrochemical impedance spectroscopy, the scale forming reactions dominate the corrosion process when the CO2 pressure is lower than 0.6MPa and the dissolution of Fe, followed by the consecutive mechanism with adsorbed intermediate products, takes up the dominant part in the anodic process when the CO2 pressure exceeds 0.6MPa.

The formation mechanism of corrosion scale and electrochemical characteristic of low alloy steel in carbon dioxide-saturated solution

The formation mechanism of corrosion scale and electrochemical characteristic of low alloy steel in CO2-saturated solution were investigated by electrochemical measurements and surface characterization. The results show that the electrochemical behavior is associated with the formation of corrosion scale and the microstructure of steel. At the initial polarization stage, ferrite dissolves preferentially and leaves Fe3C behind, which results in high Fe2+ ions concentration between lamellar Fe3C. This situation facilitates the formation of FeCO3 scale between the lamellar Fe3C. With further increase of polarization times, the whole electrode surface is covered by FeCO3 scale.

On the fundamentals of electrochemical corrosion of X65 steel in CO 2-containing formation water in the presence of acetic acid in petroleum production

Electrochemical corrosion behavior of X65 steel in CO 2-containing oilfield formation water in the presence of acetic acid (HAc) was investigated by various electrochemical measurements and analyses as well as thermodynamic calculations of ionic concentrations, reaction rate constants and equilibrium electrode potentials. A conceptual model was developed to illustrate corrosion processes of steel in oilfield formation water system. The anodic reactions of the steel contain a direct dissolution of Fe, Fe → Fe 2+ + 2e, and the formation of corrosion scale, FeCO 3, by Fe + HCO 3 - → FeCO 3 + H + + 2e. The cathodic processes contain the reduction of H +, HCO 3 - , H 2O and HAc, where reduction of HAc has the least negative equilibrium potential and thus dominates the cathodic process. With addition of HAc in the solution, both cathodic and anodic reaction rates increase remarkably. It is attributed to the fact that HAc inhibits or degrades the formation of protective scales due to the decrease of solution pH. Upon electrode rotation, the measured impedance decreases with the increase in HAc concentration. The FeCO 3 scale will not form on electrode surface. When HAc concentration is less than 1000 ppm, the adsorbed intermediate product is not significant, resulting in generation of a low-frequency inductive loop in EIS plots. When HAc concentration is more than 3000 ppm, the adsorption of intermediate product is significant, generating overlapped capacitive semicircles in EIS measurements.

The use of ternary phase diagrams in the study of high temperature corrosion products formed on Fe–5 wt% Al alloys in reducing and oxidizing environments

Ternary phase diagrams, in conjunction with microscopy techniques and reaction product chemistries, were used to describe the possible “diffusion paths” and resulting morphologies that may occur during formation of corrosion scales from high temperature gaseous exposure. Iron with 5 wt% of aluminum was exposed to reducing and oxidizing environments at 700°C. Characterization of the surface reaction products was conducted using microscopy techniques with energy dispersive spectroscopy and electron probe microanalysis. Under both conditions, iron diffused outward to form surface reaction products, either iron sulfide or iron oxide. The ingress of sulfur or oxygen through the previously formed reaction products was found to produce internal corrosion phases within the alloy. By plotting chemical information acquired from the corrosion scales on ternary phase diagrams, development of the phase layer sequence and morphologies of the multiphase corrosion scales was schematically explained. This analysis was conducted using conventions summarized by Clarke ( Trans. Am. Inst. Min. Engrs, 1963, 227, 1250) for plotting diffusion paths in multiphase ternary diffusion studies from solid-state reactions. By presenting the experimental data in this manner, the morphological development of the scales was related to the composition path on the ternary phase diagrams.

Corrosion Prevention of Waterwall Tube by Field Metal Spraying in Municipal Waste Incineration Plants

Abstract Fireside corrosion factors in high-temperature corrosion of waterwall tubes in waste incineration boilers were investigated. Factors accelerating corrosion were considered to be heavy metal (zinc and lead) chlorides, unburned carbon in deposits, and reduction of the gas atmosphere formed by the increase of unburned gas components and the decrease of oxygen (O2). Laboratory tests confirmed that increasing these factors increased the corrosion rate of carbon steel (CS). These tendencies were in good agreement with those in actual furnaces. A gas spray coating of two-layer Al/80% Ni-20% Cr, selected after laboratory corrosion tests, was applied to waterwall tubes at the test site. The Al/80% Ni-20% Cr spray coating maintained excellent durability for > 3 years, and its effectiveness in corrosion prevention was confirmed. This coating system has been applied at seven plants. Main deterioration factors affecting the coating layer were considered to be formation of corrosion scale and a decrease in bon...

The influence of dissolved oxygen concentration on the corrosion of grey cast iron in water at 50°C

The formation of corrosion scales has been studied on grey cast iron in flowing water at 50°C as a function of O 2 concentrations from 0.1 to 3.95 ppm O 2. Below 1.0 ppm O 2, nodular scales form containing Fe 3O 4 and a green rust, GR. At higher O 2 concentrations, a continuous scale eventually forms, consisting of a porous subscale of Fe 2O 4 + GR overlaid with a compact crust of Fe 3O 4 + GR and a thin surface layer of γ-FeOOH. ‘Chimneys’ oriented in the water flow direction grow out of the crust. γ-FeOOH is reduced to Fe 3O 4 which becomes the principal constituent of the scale. Scales on cast iron components from central heating systems closely resemble those found in the present work.

The role of K shell ionization in the formation of F centers in alkali halides at 78° K I. KBr

Stainless steels generally have extremely good corrosion resistance, but are still susceptible to pitting corrosion. As a result, corrosion scales can form on the surface of stainless steel after extended exposure to aggressive aqueous environments. Corrosion scales play an important role in affecting water quality. These research results showed that interior regions of stainless steel corrosion scales have a high percentage of chromium phases. We reveal the morphology, micro-structure and physicochemical characteristics of stainless steel corrosion scales. Stainless steel corrosion scale is identified as a podiform chromite deposit according to these characteristics, which is unlike deposit formed during iron corrosion. A conceptual model to explain the formation and growth of stainless steel corrosion scale is proposed based on its composition and structure. The scale growth process involves pitting corrosion on the stainless steel surface and the consecutive generation and homogeneous deposition of corrosion products, which is governed by a series of chemical and electrochemical reactions. This model shows the role of corrosion scales in the mechanism of iron and chromium release from pitting corroded stainless steel materials. The formation of corrosion scale is strongly related to water quality parameters. The presence of HClO results in higher ferric content inside the scales. Cl− and SO42 − ions in reclaimed water play an important role in corrosion pitting of stainless steel and promote the formation of scales.