Calculated Corrosion Rates Research Articles

BOILER SUPERHEATER PIPE FAILURE ANALYSIS THROUGH CORROSION RATE AND MECHANICAL PROPERTIES TESTING


 
 
 
 Superheater is a subcritical boiler component that functions to reheat saturated steam at constant working pressure so that it becomes saturated steam. This study aims to (1) analyze failures in superheaters, (2) test mechanical properties of superheater pipe materials, (3) calculate corrosion rates in superheater pipes with weight loss methods, (4) provide preventive maintenance solutions to minimize superheater pipe damage.
 The method used in this study is a qualitative approach with the type of experimental study. The method of failure analysis in this superheater pipe is by testing mechanical properties, calculating the corrosion rate of the superheater pipe and providing maintenance solutions.
 The results of this study are (1) the failure that occurs in this superheater pipe is the occurrence of corrosion and leakage, (2) after heat treatment with a temperature of 8500C on the superheater pipe material, the hardness value increases to 148 BHN, the impact value also increases to 43.26 joules and the phase that occurs in this material is ferrite and pearlite which shows the specimen is increasingly tenacious, (3) the corrosion rate that occurs in the superheater pipe is 0.0489 mmpy, (4) the workable maintenance solution is hardening to increase the durability and service life of the superheater pipe.
 
 Keywords: Superheater, Noise, Mechanical Properties, Heat treatment.
 
 
 

Improving wear and corrosion resistances of Mg2Si/AZ91 composites via tailoring microstructure and intrinsic properties of Mg2Si induced by Sb modification

To achieve simultaneous improvement in wear resistance and corrosion resistance, we propose a novel strategy to successfully develop Mg matrix composites containing blocky primary Mg2Si with small size instead of undesirable dendrite shape and large size. The tribological and corrosion behavior of Mg2Si/AZ91 unmodified and modified with 2.0wt.%Sb was subsequently and systematically investigated. The results show that Sb addition can significantly modify the morphology of primary Mg2Si to blocky polygon with smaller size of 12-25 µm, but has less effect on α-Mg grain size. Compared with unmodified composite, Sb modified Mg2Si/AZ91 composite has higher Brinell hardness and nearly unchanged microhardness of the matrix. Sb modified composite exhibits a 26% lower wear loss than unmodified composite, suggesting the greatly improved wear resistance. Microstructure analyses indicate that the main wear mechanism of composites is dominated by abrasive wear, and Sb addition can decrease the width and depth of grooves, resulting in a weakened abrasive wear behavior. Additionally, microcracks initiation on Sb modified Mg2Si particles can be restricted during the sliding friction process because of higher toughness and blocky polygonal shape induced by Sb doping, which is responsible for the improved wear resistance. Interestingly, Sb modified Mg2Si/AZ91 composite also demonstrates a superior corrosion resistance than unmodified composite due to the decrease of calculated corrosion rate from 1.57 mm/y to 0.74 mm/y, reduced by 52.8%. Such improvement is closely related to the reduced susceptibility to micro-galvanic corrosion, which is attributed to the reduced volta potential difference of Mg2Si relative to the Mg matrix, from 365 mV to 210 mV.

A reinforced corrosion assessment method based on a new magnetic sensor and improved adaptive filtering

Abstract Corrosion assessment of reinforced concrete structures is the basis for subsequent corrosion repair and early warning of structural hazards. Aiming at the problem of accurately measuring the corrosion degree of reinforced concrete structures in coastal area, a new Magnetic Sensor (NMS) based on the theory of magnetic medium is designed in this paper. A functional model of the relationship between magnetic induction intensity change and reinforcement mass loss based on multi-point detection is constructed, and an improved adaptive filtering Least Mean Square (LMS) algorithm is proposed to realize damage identification and quantitative calculation of reinforcement corrosion comprehensively. Through numerical simulation experiments, the feasibility of designing the sensor is verified. The measured corrosion test of the sensor prototype shows that the calculated corrosion rates of different steel corrosion degrees are in good agreement with the actual values, with an average relative error of 1.64 %. The sensor provides a new method for corrosion monitoring of reinforced concrete structures.

Corrosion of carbonate speleothems by bat guano

Interactions between bat guano and speleothems were studied in caves of Slovakia (Domica, Drienovská, and Jasovská caves) and Poland (Nietoperzowa Cave). This contribution focuses on the estimation of the rate of guano-induced corrosion of carbonates and on the transformations of speleothems caused by the corrosion. The intense interaction between bat guano accumulations and cave carbonates is mainly controlled by the chemical composition of guano. Corrosion of carbonates by guano leachates, suggested by negative calcite saturation index, was confirmed by weight loss of experimental carbonate tablets exposed to interaction with guano in situ in caves, and under laboratory conditions. The calculated corrosion rate of the tablets was up to 0.111 mm/y. However, measurements of selected corrosion forms in the studied caves, compared to the guano 14C age, suggest rates of the corrosion up to 0.65 mm/y. Transport of aggressive guano leachates is possible in the presence of water; increased drip water supply is considered as contributing to the higher dissolution rates. Crystallization of phosphates as byproducts of the interaction of guano with carbonates can also alter the dissolution process. Phosphates, represented by ardealite, brushite, and hydroxylapatite, were observed on the surfaces of experimental tablets and speleothems alike. Interestingly, hydroxylapatite was the only mineral associated with guano-related hiatuses within speleothem sections. Phosphates are usually accompanied by various dissolution features, such as corrosion pits and considerably dissolved calcite crystals. Dissolution features currently forming on speleothem surfaces are analogous to those identified in the fossil record. U-series dating of guano corrosion episodes within stalagmites from Domica and Drienovská caves indicates their Pleistocene age, while within a flowstone from Nietoperzowa Cave, a Holocene age. Considerable guano accumulations are common in low-latitude caves, whereas in temperate climatic zones guano accumulates irregularly in space and time. The guano accumulations are usually restricted to cave sections distant no more than few hundred meters from the nearest entrance. Considering the widespread distribution of bats across the globe, this process is expected to be common in caves. Nevertheless, the random distribution of guano in caves and its temporal deposition, but also the climate-dependent availability of water, suggest that guano-induced corrosion can be regarded as a site specific process.

Моделирование коррозии углеродистой стали с учетом различных факторов в применении к прогнозированию срока службы контейнеров

The paper overviews the studies dealing with carbon steel corrosion under underground disposal conditions. It presents a model of carbon steel corrosion considering the impact produced by bentonite taking into account oxidation kinetics, steel surface inhibition due to its blocking by corrosion products, as well as cation sorption on the bentonite material. Under the study, the model verification was carried out based on a comparation with the literature data. The simulation showed close agreement of the calculated corrosion rates with the experimental results. The findings of the study may be used to forecast the corrosion of engineered carbon steel safety barriers.

Classification and spatial mapping of atmospheric corrosion of China

Atmospheric corrosion is ubiquitous in China but varies a lot among different regions covering the cold, temperate, and tropical zones. Categorizing the atmospheric corrosivity and plotting precise atmospheric corrosion map remain key interest for a variety of industries. The present work proposed an atmospheric corrosion map of China for hot-dip galvanized steels, which was constructed by inverse distance weighting (IDW) interpolation algorithm based on both the measured corrosion rates of coupons exposed at 2393 inland test stations and calculated corrosion rates from a prevalent dose-response function in 2918 sites in coastal regions. When the corrosion category was used as the criterion, the IDW interpolation algorithm of power 2 performed best. Cross-validation results confirmed that the prediction accuracy of IDW interpolation reached 85.6%. Based on the corrosion map, the categories of atmospheric corrosivity in China could be determined.

When material science meets microbial ecology: Bacterial community selection on stainless steels in natural seawater

The passive film depends on the alloy's composition and the exposure conditions. How the surface composition affects the selection of microbial biofilms though, has not been fully elucidated or incorporated into the analysis of corrosive biofilms. The degradation of stainless steel (SS) exposed to natural seawater was studied to understand how the oxide layer composition of SS could affect the selection and variability of the bacterial community. To accomplish this goal, austenitic and superferritic SS grades were exposed to natural seawater on the central coast of Chile. The deterioration of steel and qualitative description of biofilm formation was monitored at different exposure periods. Biofilms were evaluated based on massive sequencing analysis of the bacterial community and subsequent ecological studies. The results revealed that variability of the calculated corrosion rate correlated with the similarity of the bacterial community within samples from each SS and its corrosion inferred capacity. The associated bacterial families showed a higher representation in SSs with a more significant increase in the Fe/Cr ratio over the exposure time. These findings revealed that iron content in the oxide layer represents a key feature of the surface composition for selecting bacterial assemblages in marine environments.

Simulation of CO2 Corrosion of Carbon Steel in High Pressure and High Temperature Environment (HPHT)

In HPHT environments, the mechanism of CO2 corrosion faces a challenge as an effect of chemical-physical reactions on the metal surface. The presence of other elements in the CO2 system complicates corrosion behavior. To provide a realistic mechanism for corrosion process, some corrosion prediction models have developed software using fundamental theories such as electrochemical reactions and thermodynamics theories. Existing methods to predict corrosion rate models in HPHT environments have shown reasonable results. This paper reviews software of corrosion predictions which calculate corrosion rate based on mechanistic theories that study effects of H2S, acetic acid (HAc) concentrations, shear stress, pH in temperature from 25oC – 100oC and pressure from 1–10 bar. From the simulation, corrosion rate increased significantly in the high pressure CO2 environment. Corrosion rate at pH 4 increased to 30 mm/y at a temperature from 15oC to 90oC. While at pH 8 corrosion rate reached 4 mm/y. This lower corrosion rate indicated a tendency for deposits formation at higher pH. Corrosion rate behaves in a different mechanism at high temperatures. The corrosion rate decreased to 4 mm/y when the temperature increased to more than 90oC. Effects H2S gas and HAc were identified to increase corrosion rate. Both elements provide extra cathodic reaction and create limiting current density in the cathodic reaction process based on polarization sweep models. However, the polarization graph calculated using corrosion models could not display passive behavior in the anodic polarization process. Thus, further, improvement should be considered. From the data calculation, it can be shown that corrosion prediction software can predict corrosion rate in HPHT conditions.

Investigation of Carboxymethyl Cellulose and Barite Additives on the Corrosion Characteristics of Water-Based Drilling Mud

Drilling fluids can be considered complex liquids containing several desired materials. These materials (small additives) are specialty products that serve a specific need, such as controlling the rheological properties of the drilling fluid and reducing corrosion for operational drilling of both oil and gas wells. Additives used to resist corrosion are called corrosion inhibitors. Previous research has shown that polymers such as Carboxymethyl Cellulose (CMC) have high characteristics of corrosion inhabitation in an aggressive environment. In this study, the effect of adding two samples of additives, CMC and Barite, on the corrosion of carbon steel in Iraqi bentonite water base mud solution has been evaluated using the weight loss technique. The study focuses on determining and comparing the corrosion characteristics of these mud additives. All the experiments were carried out in static flow and at room temperature. Results show that CMC works as a good inhibitor when added to bentonite/barite mud. The calculated corrosion rates of 0.95mpy, 0.75mpy, 0.53mpy, 0.49mpy were found for bentonite mud, bentonite/barite mud, bentonite/CMC mud, and bentonite/CMC/barite mud, respectively. This would result in an inhibitor efficiency of about 50%.

Analysis of prolonged marine exposure on properties of AH36 steel

Corrosive marine environment has negative impact on welded steel structures, so it is necessary to investigate the effect of sea exposure on such materials. This research investigates the change of mechanical properties and surface condition of AH36 shipbuilding steel butt-welded specimens exposed to natural marine environment for prolonged periods (6, 12 and 24 months). Contrary to accelerated tests in simulated laboratory environment, this approach is rarely used. Engineering stress–strain diagrams are obtained using standardized procedures for uniaxial tensile tests, giving insight into the change of material strength due to length of exposure and type of corrosive environment (water, sea water, sea waves). Using impact tests, values of measured Charpy impact energy are given. Additionally, relative mass change over time is given along with calculated corrosion rates. Corroded surface is microscopically inspected and comparison, based on number and dimensions of corrosion pits in the observed area, is given.

Corrosion Experimental Research on Local Damage of Epoxy-Coated Steel Bars in Concrete Under Marine Environment

Epoxy coating has been proven to protect steel bars from corrosion. However, the damage of epoxy coating is inevitable, and this may lead to more serious corrosion of steel bar. In order to study the corrosion resistance of steel bars with damaged epoxy coating, two groups of coating-damaged bar and one group of coating-intact rebar were designed, and six specimens were made. The influence of electrolyte concentration on the corrosion rate of steel bars was studied by setting different concentrations. After 30 days of accelerated corrosion, electrochemical data were recorded by the electrochemical workstation. The experimental result shows that the steel bars with coating damage have obvious polarization curve characteristics of corrosion, and corrosion resistance decreases obviously. According to the corrosion current and potential, the larger the damaged area of the coating, the faster will be the corrosion rate. According to the polarization curve data, the polarization resistance is modified, and the result is closer to the real polarization resistance value. The calculated corrosion rate shows that the corrosion rate of reinforcement is affected by both electrolyte concentration and coating damage area, and electrolyte concentration has a greater influence on the corrosion rate.

Electrolyte Based Modeling of Corrosion Processes in Sulfuric Acid Mixtures, Part 1: Nonoxidizing Conditions

The corrosion behavior of stainless steels and Ni-based alloys in nonoxidizing sulfuric acid mixtures at concentrations below approximately 30 mol/kg H2O is modeled. The redox potential in sulfuric acid across a broad concentration range, from 0 to 80 mol% (0 to 95.6 wt%), is determined by the proton reduction reaction. Thus, in the absence of other oxidizing species, sulfuric acid behaves as a nonoxidizing (reducing) acid. The calculated corrosion rates, using an electrochemical model up to about 30 mol/kg H2O (about 75 wt%), are in agreement with experimental values. The predicted polarization curves of anodic and cathodic processes show that the alloys in these environments are in active dissolution regime, consistent with experimental data. The model predictions of corrosion rates in H2SO4+HCl, H2SO4+HF, and H2SO4+HCl+HF mixtures are in agreement with weight-loss corrosion data. The corrosion rate of alloys in the nonoxidizing sulfuric acid mixtures correlated to an equivalent alloy composition given by (Ni0.7-Cr0.1+Mo+0.5 W). The effect of alloying elements under these conditions may be related to their beneficial effect on active dissolution and proton reduction reaction rates.

Bifunctional poly (l-lactic acid)/hydrophobic silica nanocomposite layer coated on magnesium stents for enhancing corrosion resistance and endothelial cell responses

Biodegradable magnesium (Mg)-based vascular stents can overcome the limitations of conventional permanent metallic stents, such as late in-stent restenosis and thrombosis, but still have difficulty retarding degradation while providing adequate mechanical support to the blood vessel. We incorporated silica nanoparticles surface-functionalized with hexadecyltrimethoxysilane (mSiNP) into a poly (l-lactic acid) (PLLA) coating as a physical barrier to disturb the penetration of the corrosive medium as well as a bioactive source that releases silicon ions capable of stimulating endothelial cells. The corrosion resistance and biocompatibility of this bifunctional PLLA/mSiNP nanocomposite coating were investigated using different weight ratios of mSiNP. The nanocomposite coating containing more than 10 wt% of the mSiNP (PLLA/10mSiNP and PLLA/20mSiNP) significantly delayed the corrosion of the Mg substrate and exhibited favorable endothelial cell responses, compared to the pure PLLA coating. Specifically, the calculated corrosion rates of PLLA/10mSiNP and PLLA/20mSiNP decreased by half, indicating the durability of the coating after immersion in simulated body fluid for 12 days. Based on the in vitro cellular response, the incorporation of the mSiNPs into the PLLA coating significantly improved the endothelial cell responses to the Mg substrate, showing better initial cell surface coverage, migration, and proliferation rate than those of pure PLLA. These results indicate that the PLLA/mSiNP nanocomposite coatings have significant potential to improve the corrosion resistance and vascular compatibility of biodegradable Mg-based vascular stents.

Long-Term Marine Environment Exposure Effect on Butt-Welded Shipbuilding Steel

Extreme environments, such as marine environments, have negative impacts on welded steel structures, causing corrosion, reduced structural integrity and, consequently, failures. That is why it is necessary to perform an experimental research sea exposure effect on such structures and materials. Research presented in this paper deals with the mechanical behavior of butt-welded specimens made of AH36 shipbuilding steel when they are exposed to a natural marine environment (water, seawater, sea splash) for prolonged periods (3, 6, 12, 24, and 36 months). The usual approach to such research is to perform accelerated tests in a simulated laboratory environment. Here, relative mass change due to corrosion over time is given along with calculated corrosion rates. Corroded surfaces of specimens were inspected using optical and scanning electron microscopy and comparison, based on the numbers and dimensions of the corrosion pits (diameter and depth) in the observed area. As a result, it can be concluded that exposure between 3 and 6 months shows significant influence on mass loss of specimens. Further, sea splash generally has the most negative impact on corrosion rate due to the combined chemical and mechanical degradation of material. Pit density is the highest at the base metal area of the specimen. The diameters of the corrosion pits grow over the time of exposure as the pits coalesce and join. Pit depths are generally greatest in the heat affected zone area of the specimen.

Modeling research of initial atmospheric corrosion of Q235 carbon steel based on electrical resistance probe

PurposeThis paper aims to discover the mathematical model for Q235 carbon steel corrosion date acquired in the initial stage of atmospheric corrosion using electrical resistance probe.Design/methodology/approachIn this paper, mathematical approaches are used to construct a classification model for atmospheric environmental elements and material corrosion rates.FindingsResults of the experiment show that the corrosion data can be converted into corrosion depth for calculating corrosion rate to obtain corrosion kinetics model and conform corrosion acceleration phase. Combined with corresponding atmospheric environmental elements, a real time grade subdivision model for corrosion rate can be constructed.Originality/valueThese mathematical models constructed by real time corrosion data can be well used to research the characteristics about initial atmospheric corrosion of Q235 carbon steel.

Numerical Modeling for Corrosion Rate between Heat-affected Zone and Unaffected Base Metal of Galvanized Steel Welded by Brazing

Brazing of galvanized steel causes decaying of the zinc coating and decreasing of corrosion resistant on heataffected zone (HAZ) and weldment. The corrosion rates among the HAZ, unaffected base metal (UBM), and weldment of galvanized steel welded by brazing were numerically modeled by COMSOL Multiphysics. The numerically modeled current density values from various zones, such as the couples between the HAZ and the UBM, between the weldment and the HAZ, and between the UBM and steel were used to calculate the corrosion rates. In this work, two different methods based on Faraday’s Law, the mixed potential theory and the Numerical modeling, were compared for calculations of the corrosion rates of each region. Using the mixed potential theory, the calculated corrosion rates of region I, II, III, IV, V and VI were 0.853, 0.284, 2.105,1.754, 2.028 and 0.554 mm/y, respectively. Where as based on the Numerical modeling, these rates of all regions were 0.918, 0.275, 2.198, 1.904, 2.151, and 0.566 mm/y, in orderly. These comparisons suggested that the corrosion rates obtained from two methods were similar. However, the results showed that the Numerical modeling method could predict the corrosion rate with less error.

Corrosion and mechanical behavior of plasma nitrated metallic biomaterial surfaces

Biomaterials are the materials that are used to replace a biological tissue or support the system. The most commonly used metal SS316L and another metal Ti6Al4V which has the desired properties selected for improving their feasibility. SS316L and Ti6AL4V though being highly resistant to corrosion, show corrosive properties while used in a biological system. So, they need to be made much compatible while using it as a biomaterial thus plasma nitriding is done and the rate of corrosion is reduced making it much more compactable as a biomaterial. Plasma nitriding is a heat treatment process that diffuses nitrogen ions through the surface i.e. form nitrides and reducing the reactivity and thus improving the corrosion resistance. These metals are nitrided for different periods of 8 h and 24 h separately and the changes in the properties are studied using various tests. An electrochemical corrosion test is done to calculate corrosion rates. SEM and EDAX are done to study the structural topography and composition respectively. Vickers hardness test is done to show the effect of plasma nitriding on the hardness of the metals. On studying all the test results the better metal suitable as a biomaterial is determined.

Faktori sigurnosti u proračunu debljine zida kolona za rektifikaciju

Gas rectification columns are a very important part of each onshore plant. Their sudden failures cause huge losses on a daily basis, while fluid leakage can be very dangerous to people and environment. For that reason, the proper design of the column is of huge importance, among the others safety factors as well. In this paper, the wall thickness measure is presented with the aim to calculate corrosion rate and remaining life of rectification columns. The minimum required column wall thickness was calculated according to the most commonly used international standard and the obtained difference was analyzed.

Composite tube damage evaluation in aggressive oil-gas field

The purpose of this article is to lead a research program to assess the damaging of liners of a composite tube for operation in oil-gas fields containing carbon dioxide, including those with minor amounts of hydrogen sulfide at standard conditions and under conditions of elevated temperature and pressure. To assess the level of corrosion resistance of the composite tube liner, stress corrosion cracking tests were carried out, autoclave tests for general corrosion at elevated temperatures and pressures were also carried out, and electrochemical studies were carried out to assess the equilibrium corrosion potential and calculate corrosion rates analyzing Tafel curves.

Productivity Performance Estimation in Egyptian Construction Projects Based on Regression Analysis (Dept.C)

Reinforcement corrosion is the main cause of damage and early failure of reinforced concrete structures. The protection system of embedded steel reinforcement from chloride induced corrosion involves several methods and techniques. One of these methods and techniques is using corrosion inhibitors admixtures (CIA) which added to concrete mix during mixing stage of concrete. These research aims to evaluate these admixtures (Sika Ferrogard®-901) in prevent corrosion of steel in concrete and their effect on concrete properties for fresh and hardened concrete. In this paper (CIA) used with different concrete contents and proportions. In this study, 150-mm concrete cubes specimens with high tensile steel bar grade (36/52) of 10 mm in diameter and 150 mm in length were embedded in each specimen during its casting such that 100 mm was fixed inside the concrete while the reminder 50 mm was kept outside. Three thicknesses of concrete cover were used; 25, 50 and 75 mm. After 28 days of water curing, specimens were transferred to dry for 24 hour, then the specimens were partially submerged in plastic tank filled with 6% NaCl solution Acceleration of corrosion rate test is achieved by continuous electrical current produced from power supply 30 volts for 240 hour, where volts difference was measured in volts between resistance 100 ohm and the reading was record every 12 hour. The corrosion current (Icon in Ampere) was calculated during the accelerated corrosion regime by using ohm's law by knowing measured volts difference and resistance. Faraday's law describes the relationship between section loss and corrosion current. Hence, calculate corrosion rate of steel reinforcement in concrete. The results show that for all mixes the increasing of concrete cover thickness reduces the corrosion rate of steel. Using 5% (CIA) by weight of cement where the optimum dosage of Corrosion inhibitors admixture from experimental tests is 5% by weight of cement reduce corrosion rate by 80 % with no side effect on concrete properties except bond strength decreased by 10%.(CIA) gave best results with concrete mixes which contains 15% silica fume and water to cement ratio 0.35 · (CIA) decreasing concrete cover required to prevent corrosion from 75 mm to 50 mm. (CIA) accelerate setting time of concrete, so it needs a retarded when used with concrete mixes.