Deposition Of Corrosion Products Research Articles

Characterizing archaeological bronze corrosion products intersecting electrochemical impedance measurements with voltammetry of immobilized particles

Application of electrochemical impedance measurements to microparticulate deposits of copper corrosion products attached to graphite electrodes in contact with 0.10M aqueous HClO4 electrolyte is described. The impedance measurements were sensitive to the applied potential and the amount of solid sample and were modeled taking into account the contribution of the uncovered base electrode. Several pairs of circuit elements provide monotonic variations which are able to characterize different corrosion compounds regardless the amount of microparticulate solid on the electrode. Application to a set of archaeological samples from the archaeological Roman site of Gadara (Jordan, 4th century AD) permitted to establish a grouping of such samples suggesting different provenances/manufacturing techniques.

Microstructure and corrosion behavior of Ca/P coatings prepared on magnesium by plasma electrolytic oxidation

In order to enhance the corrosion resistance and biocompatibility of Mg based implants, porous MgO-CaP coatings were fabricated on commercial Mg by adding hydroxyapatite (HAp) particles in alkaline phosphate solution for plasma electrolytic oxidation (PEO) treatment. The effects of particle concentration on the coating morphology and composition were investigated under constant current PEO processing. Electrochemical impedance spectroscopy (EIS) and immersion test conducted in simulated body fluid (SBF) environment were applied to evaluate the corrosion performance of the coatings. The results showed that most HAp particles were reactively incorporated into the PEO coatings and the coating microstructure was significantly modified with increasing concentration of HA, which resulted in higher corrosion resistance in return. The consecutive growth of impedance during 72h immersion resulted from the precipitation and deposition of CaP compound and corrosion product into the pores sealing the defects of PEO coatings. Overall, a higher concentration (20g/L) of HAp particles addition would bring out a denser and protective PEO-HAp coating.

Microstructural analysis and corrosion behavior of Fe, B, and Fe-B-modified Cu-Zn-Al shape memory alloys

AbstractThe corrosion behavior of Cu-Zn-Al alloys modified with Fe, B, and Fe-B was investigated. This was motivated by the need to verify the effect of microalloy additions on the corrosion behavior of Cu-Zn-Al alloys, which, as recent study suggests, impacts microstructural changes other than grain refinement. Cu-Zn-Al alloys were produced by casting method with and without the addition of microalloy elements. The alloys were subjected to thermomechanical treatment before machining of test samples for corrosion and microstructural analysis. Scanning electron microscopy (SEM) and polarization electrochemical technique were used for the study. From the results, increase in grain size and change in grain edge morphology was apparent for the modified Cu-Zn-Al alloys produced. In 3.5 wt.% NaCl and 0.3mH2SO4solutions, the corrosion current densities were dependent on the type and concentration of the microalloy addition. Essentially, the corrosion rates for the modified alloys were higher in 3.5 wt.% NaCl solution; in 0.3mH2SO4solution, the modified Cu-Zn-Al alloy grades were observed to be more resistant to corrosion. The corrosion mechanisms of the alloys in both solutions were not feasibly established from the SEM images, but the extent of corrosion product deposition was apparent.

Examinations of a Bronze Ingot Made of Fahlore

Abstract In Europe, the metallurgy of copper has been a tradition for thousands of years, which is also testified by relevant artifacts that can be found. A copper ingot of unknown origin was made available for the examinations. The surface of the ingot was characterized by a deposit of corrosion products from malachite and cuprite which could also be observed in cavities. XRF measurements resulted in Cu as the main component, up to 4 wt. % As, and 2.5 wt. % S, as well as smaller quantities of Sb, Ni, Fe, and Ag. This composition suggests the production from fahlores. A typical cast structure with copper dendritic areas and concentrations of the accompanying elements in the interdendritic areas could be observed. Delafossite crystals (Cu3Ni2SbO6) were verified on the ingot's top side (melt in contact with the air). The ingot is thus composed of an As bronze with a complex microstructure consisting of solid solutions, intermetallic phases, and sulfides.

The role of corrosion product deposition in galvanic corrosion of aluminum/carbon systems

This study is concerned with the role of corrosion product deposition in the galvanic corrosion between aluminum and Carbon Fiber Reinforced Polymer matrix composite (CFRP). The galvanic corrosion of a high voltage conductor assembly consisting of a cylindrical CFRP rod surrounded by tightly wound aluminum wires has been investigated through experimental work and modeling. The main corrosion product is Al(OH)3, which presents as a gelatinous substance in the crevices between the Al wires. The formation of Al(OH)3 was observed to coincide with the decay in the galvanic corrosion current. A new analytical model was developed to investigate if the decay could be caused by corrosion products restricting the transport of oxygen to the cathode. Modeling of the oxygen diffusion through the deposited corrosion products generated galvanic corrosion rates that agreed well with the experimental measurements after an early exponential decay period. The findings suggest that the corrosion product deposition may be the most important galvanic corrosion rate controlling mechanism in this geometry and similar geometries.

Effect of Stress on Corrosion at Crack Tip on Pipeline Steel in a Near-Neutral pH Solution

In this work, the local corrosion at crack tip on an API 5L X46 pipeline steel specimens was investigated under various applied loads in a near-neutral pH solution. Electrochemical measurements, including potentiodynamic polarization and electrochemical impedance spectroscopy, combined with micro-electrochemical technique and surface characterization, were conducted to investigate the effect of stress on local anodic solution of the steel at the crack tip. The stress corrosion cracking of the steel was dominated by an anodic dissolution mechanism, while the effect of hydrogen was negligible. The applied load (stress) increased the corrosion rate at the crack tip, contributing to crack propagation. The deposit of corrosion products at the crack tip could protect somewhat from further corrosion. At sufficiently large applied loads such as 740 N in the work, it was possible to generate separated cathode and anode, further accelerating the crack growth.

Impact of Complex Layering Structures of Organic and Inorganic Foulants on the Thermohydraulic Performance of a Single Heat Exchanger Tube: A Simulation Study

Crude oil fouling in preheat trains in refineries is usually dominated by organic matter deposition at high temperatures. However, malfunction of desalting equipment, human or technical errors, or changes in feedstock may lead to substantial deposition of inorganic salts or corrosion products, compromising heat exchange performance, pressure drop (hence throughput), and even safety. Understanding how such abnormal deposition and the resulting complex deposit structure affect the thermohydraulic performance of heat exchangers is key to developing adequate monitoring tools for the early detection, diagnosis, and control of the underlying causes. Here, a novel multicomponent fouling deposit formulation is applied to the simulation of deposits composed of organic and inorganic foulants within a single heat exchanger tube. The model enables the tracking of changes and history of local composition in the fouling deposit, thermoconductivity profiles including layering effects, and impact on the overall thermohyd...

Influence of Corrosion Product on Corrosion Behavior of Carbon Steel in Atmospheric Environment

Atmospheric corrosion proceeds under thin water film, and it is affected by many environmental factors such as temperature, relative humidity, rainfall, deposition of airborne sea salt. Most of the previous study of atmospheric corrosion of carbon steel has been focused on the corrosion behavior in initial corrosion process. However, corrosion products are formed on the surface at an early stage in case of carbon steels. Thus it is important to clarify the influence of corrosion products on atmospheric corrosion behavior.. While corrosion products may easily lead to wet condition with absorption of moisture, it is reported that corrosion products inhibit the corrosion physically or chemically. In this study, we focus on dew condensation which occurs on the surface of carbon steels with rust layer. The electrodes with corrosion products were prepared by wet/dry cyclic corrosion test. The remodeled concentric corrosion sensor was used as the electrodes. The temperature of electrode materials can be controlled from the backside of electrode because the backside of the remodeled sensor is exposed to atmosphere. The corrosion test was carried out in a chamber at 25℃ and 60％RH by adding the droplet of 0.1M NaCl solution or distilled water. During the corrosion test, the corrosion rate of the electrode was monitored by electrochemical impedance method. The electrode covered with corrosion products was cooled with a cooling equipment in the chamber at 25 ℃ and 60 ％ RH in order to measure the dew point. The dew point was evaluated by measuring solution resistance using electrochemical impedance method. The dew point of the electrode before corrosion test was measured. The solution resistance dropped sharply to a low value at around 17 ℃. The dew point was calculated at 17℃ under the 25℃ and 60％RH from the curve of saturation water vapor pressure and Tetens’s equation, indicating that the experimental and calculated values are in good agreement. The amount of corrosion products increased with an increase of the cycle number. The solution resistance of the electrode after corrosion test went down at the temperature higher than the calculated value. In addition, the deposition of corrosion products occurred an increase of the dew point of the electrode. This is attributed to the diameter of pore in rust layer. It is known that equilibrium water vapor pressure in the crevice increases with a decrease of the crevice size. This means that the humidity in crevice increases in comparison with relative humidity of atmosphere. It is predicted the deposition of corrosion products leads to the formation of smaller size of pores. The chloride ion is included in the rust layer, and thus the water absorption of chloride ion occurs even at higher surface temperature.

Hydrothermal Surface Treatments with Cerium and Glycol Molecules on the AA 2024-T3 Clad Alloy

New treatments for replacement of chromate require lower toxicity and corrosion protection. This study aims to investigate the influence of the combination of a Ce conversion coating (CCCe) with glycol molecules on the corrosion resistance of the AA2024-T3 clad (AA1230). The corrosion resistance of surface treated and untreated samples was evaluated by electrochemical techniques (electrochemical impedance spectroscopy, polarization tests and open circuit potential). These tests were complemented by salt spray tests to accelerate the corrosive effects of weathering. The surfaces were analyzed after corrosion tests by scanning electron microscopy with X-ray energy dispersive detector (SEM - EDX). The results of the CCCe samples in combination with glycol were compared with that of the surface with chromate layer and the results showed that the CCCe treatment is a candidate for replacement of chromating with the advantage that it does not generate toxic residues. The self-healing capacity of the new treatment tested was indicated by the increased formation of corrosion products deposition on top of Fe rich intermetallis in the AA1230 clad with time of exposure to the electrolyte.

Substantiation of FAC rate and service life estimation under operation control data

Flow-accelerated corrosion (FAC) wear is the complex mechanism of damage of elements of NPP equipment and pipelines. FAC rate is determined by such factors as corrosion of metal, flow hydrodynamics, geometry of equipment elements and pipelines, applied water chemistry regimes (WCR), duration of operation, chemical composition of the metal, thickness of deposited corrosion product film and others. Approaches to the assessment of FAC rate according to the control data are addressed in the present study. Implemented investigation was aimed at the substantiation of the methodology of calculation of FAC rate. Absence of the methodology for calculation of FAC rate does not allow verification of calculation programs, as well as the use of data of regulatory documents on the minimum permissible thicknesses [1] for evaluating the residual lifetime.Processing of measured data allowed determining the main indexes of FAC process such as the values of wall thinning and thickening, rates of wall thinning and thickening, residual operation time to the moment of reaching the minimum permissible thickness. Reduction of thickness is determined by corrosion of metal and its increase is determined by the formation of deposited film of corrosion products.The process of corrosion products deposition on the internal surfaces of the element proceeds simultaneously with the process of thinning of the wall. Presence of this process results in the situation when the residual lifetime of equipment elements under the conditions of deposition of corrosion products is technically increased. At the same time the real state of the wall under the layer of deposited corrosion products is unknown, as well as the initial wall thickness. In order to bring the calculated results closer to the real situation it is necessary to use substantiated and verified methodology in the calculations of FAC rate according to the data of control measurements. The implemented study allowed suggesting the methodology of calculation of FAC rate taking into account the technological tolerances on the sizes and taking into account the influence of deposits on the initial and minimum thicknesses. Safety factor was also introduced for calculating the residual lifetime which is taken into account in the international practices because of the same reason.Introduction of correction coefficients allows enhancing the conservatism of calculations of residual lifetime characteristics by approximately 2.5 times compared with calculations performed on the base of nominal thickness.

Estimating Critical Corrosion for Initiation of Longitudinal Cracks in RC Structures Considering Phases and Composition of Corrosion Products

AbstractPremature deterioration and reduction in the life of reinforced concrete (RC) structures due to corrosion of the embedded reinforcing steel bars is a major concern across the world, and the time for formation of longitudinal cracks has been largely accepted as the “service life” of the structure. It is also widely known that the formation and deposition of expansive corrosion products (of iron) on the bars exert radial pressure on the cover concrete, which finally cracks. In this case, it is reasonable to assume that the composition of the corrosion products, in terms of the different phases of the oxides and hydroxides, and their relative percentages, play a vital role in determining the loss of weight (of iron) that causes sufficient pressure for the onset of such longitudinal cracks. It is interesting that virtually no quantitative information is available in the literature on this subject. The main thrust of the present work is to understand the effect of composition and relative amount of dif...

고온화학세정환경에서 20 % EDTA 용액이 결함 전열관 (Alloy600)에 미치는 영향

The transport and deposition of corrosion products in pressurized water nuclear reactor (PWR) steam generators have led to corrosion (SCC, denting etc.) problems. Lancing, mechanical cleaning and chemical cleaning have been used to reduce these problems. The methods of lancing and mechanical cleaning have limitations in removing corrosion products due to the structure of steam generator tubes. But high temperature chemical cleaning (HTCC) with EDTA is the most effective method to remove corrosion products regardless of the structure. However, EDTA in chemical cleaning aqueous solution and chemical cleaning environments affects the integrity of materials used in steam generators. The nuclear power plants have to perform the pre-test (also called as qualification test (QT)) that confirms the effect on the integrity of materials after HTCC. This is one of the series studies that assess the effect, and this study determines the effects of 20 % EDTA aqueous solution on defective tubes in high temperature chemical cleaning environments. The depth and magnitude of defects in steam generator (SG) tubes were measured by eddy current test (ECT) signals. Surface analysis and magnitude of defects were performed by using SEM/EDS. Corrosion rate was assessed by weight loss of specimens. The ECT signals (potential and depth %) of defective tubes increased marginally. But the lengths of defects, oxides on the surface and weights of specimens did not change. The average corrosion rate of standard corrosion specimens was negligible. But the surfaces on specimens showed traces of etching. The depth of etching showed a range on the nanometer. After comprehensive evaluation of all the results, it is concluded that 20 % EDTA aqueous solution in high temperature chemical cleaning environments does not have a negative effect on defective tubes.

Discerning different and opposite effects of hydrogenase on the corrosion of mild steel in the presence of phosphate species

Mild steel coupons were exposed to hydrogenase in a 10mM phosphate solution. Control coupons were covered by a layer of vivianite. The injection of hydrogenase caused a fast increase in the open circuit potential; this increase depended on the amount of hydrogenase injected and increased from 8mV for 30μL hydrogenase to 63mV for 80μL. The presence of enzyme resulted in a thicker deposit: high amounts induced the accumulation of corrosion products. Hydrogenase that was deactivated by air revealed a protective effect: non-degradation was observed. In contrast, hydrogenase that was denatured by heat provoked an important deposit of corrosion products with a heterogeneous, cracked structure. The study showed that the action of hydrogenase is not linked to its regular enzymatic activity but to a balance between the protective effect of its protein shell and the electrochemical action of its iron-sulphur clusters. Depending on the operating conditions, hydrogenase can either enhance or mitigate the formation of a corrosion layer on mild steel.

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.

Characterization of solid particles sampled from condensates in boiling water reactor

The growth, activation and deposition of corrosion products are the primary sources of radiation buildup on the surface of out-of-core piping in nuclear power plants. The buildup of radiation can have negative effects on the performance of the facility and cause harm to staff during maintenance outages for refueling. This paper reports on the crystalline and amorphous structures of corrosion products sampled in the boiling water reactors in nuclear power plants of Kuo-Sheng and identified using an acid dissolving technique. X-ray diffraction, scanning electron microprobe and inductively coupled plasma-atomic emission spectroscopy were used to analyze the samples. The results indicate that the quantity of amorphous iron oxide at inlet of the condensate demineralizer in Unit 2 is higher than that in Unit 1. The proportion of crystalline to amorphous corrosion products can affect the efficiency of removal. Thus, these results can be used to explain the difference in removal efficiency of condensate demineralizers in different units. Moreover, the iron oxide structures with various properties were observed in different operational periods. It is probable that the higher proportion of amorphous structures with a smaller particle size would reduce efficiency in the removal of condensate demineralization in Unit 2.

A FEM model for investigation of micro-galvanic corrosion of Al alloys and effects of deposition of corrosion products

A finite element method model has been elaborated aiming at a deeper insight into the influence of microstructure on micro-galvanic corrosion of Al alloys. The model considers a dynamic corroding surface and takes into account kinetic data from local electrochemical reactions, transport of O2 and ionic species (e.g., Al3+, H+, Cl−), homogeneous reactions in the electrolyte, deposition of reaction products and its influence on both anodic and cathodic reactions. As a first step, an Al matrix with a micrometer-sized cathodic intermetallic particle exposed in 0.1M NaCl has been considered. The simulation predicts the dynamic changes of the corroding surface, and the flow and distribution of ionic species and of O2 in space and time. The calculated pH of the electrolyte inside and nearby the occluded corroding volume suggests the formation of insoluble Al(OH)3 on both the cathodic and anodic areas. This results in blocking effects of anodic and cathodic reactions and in eventual termination of the micro-galvanic corrosion. The predicted deposition of corrosion product is in good agreement with in-situ atomic force microscopy measurements.

Corrosion Resistance of API5L X52 Carbon Steel in Sulfide Polluted Environments

In the present work, the corrosion behavior of base and welded API5L X-52 carbon steel coupons in synthetic ground water solution NS-4 was studied. Subsequently, the morphology and composition of the corrosion product deposits were determined using scanning electron microscopy (SEM). Based on weight loss as well as Tafel’s measurements, increasing the sulfide ions content above 0.4 mM, had an inhibition effect on the corrosion behavior of carbon steel. According to EDAX analyses, increasing of sulfide concentration from 0.4 to 4 mM Na2S, the Fe/S ratio decreased from 12.02 at 0.4 mM to 2.6 at 4 mM Na2S.

Factors that affect the behavior of CoCrMo taper junctions under cyclic loading

Event Abstract Back to Event Factors that affect the behavior of CoCrMo taper junctions under cyclic loading Matthew A. Di Prima1, Oleg Vesnovsky1, L D Timmie Topoleski1, 2 and Paul Kovacs3 1 FDA, CDRH/OSEL, United States 2 UMBC, Mechanical Engineering, United States 3 Consultant, Electrochemistry/Biocompatibility, United States Introduction: Artificial joints are one of the most successful treatments for arthritis; however, artificial joint failure is still a critical issue. For example, wear and corrosion at different modular junctions are thought to be instigators of artificial joint failure[1]. To achieve uniform and predictable contact between the stem and head, it is important to optimize the surface structure and properties, along with the angle mismatch, straightness, and conicity of the taper and trunnion[2],[3]. The purpose of our work was to investigate geometric parameters of four different Co-Cr taper junction designs: A, B, and C with fine-machined tapers and coarse-machined trunnions; and D with ground tapers and trunnions. Design A had a negative taper angle mismatch (taper angle > trunnion angle), while C had a positive one. B and D had no taper angle mismatch. Methods: Cyclic fatigue tests (n=3 for each design) were conducted in PBS solution at 37°C at 10Hz with a loading range from 280 N (minimum) to 2800 N (maximum). Tests were run for 10 million cycles. Displacements between the taper and trunnion were measured at each million cycles with digital extensometers during loading cycles. After 10 million cycles, the force required to separate the head and stem was measured. A head welded to a stem, preventing relative motion, was tested as a control. A composite digital image of each component was created using a Hirox digital microscope and a Bruker optical profilometer[1], through 360o over the trunnion and taper surfaces. Co and Cr ion concentrations in the test fluid were measured by ICP-MS. Results and Discussion: The changes in average surface roughness and visual appearance showed different trends and magnitudes for tapers and trunnions (Fig. 1). Changes in surface roughness should reflect assembly deformation/damage to, and in-use wear on, the machining marks, as well as metal removal by corrosion and material buildup due to corrosion product deposition. At the minimum load, all four designs showed "pistoning" while at the maximum load design A exhibited a much higher level of “rocking” relative motion (Fig. 2). The measured micromotion did not appear to reflect changes in surface roughness. The separation force was lower for design B only (Fig.3), which was the smooth taper – rough trunnion combination without any angle mismatch. The trends in Co ion concentrations and Co/Cr ratios (Fig. 3) suggest that design A exhibited the greatest overall corrosion. The change in the Co/Cr ratio is likely a change in mechanism from wear and fretting corrosion to predominantly crevice corrosion. Conclusions: A combination of experimental techniques can provide a better understanding of taper junction performance. Our results show that the geometry of the taper junction can affect wear and corrosion; however, more study is needed to assess the details of the optimum design parameters. Ideally, taper-trunnion interfaces should neither move relatively to each other while in physical contact nor undergo accelerated corrosion due to the presence of a liquid. It is essential to identify physical contact points, surface roughness changes, types of locking and loosening due to mechanical forces/damage, as well as the source(s) of soluble and insoluble corrosion products.

Biological and chemical corrosion of cement materials modified with polymer

AbstractThe article presents the effect of the addition of polymer to mortars with CEMI and its influence on durability under conditions of sulfuric acid or nitric and sulphur bacteria or nitrogen (nitrification and denitrification). Both acids corresponds to the products of metabolism of bacteriaAcidithiobacillus thiooxidansandThiobacillus denitrificans,Paracoccus denitrificansby the literature is about 0.15 mmol/dm3. The changes in tightness materials studied by determining moisture mass and absorption. Corrosion processes were identified by examination in a scanning microscope equipped with an X-ray microanalyzer and a mercury porosimeter. The research results presented showed that the solution has a significantly weaker effect on the composite cement and cement-polymer compared with the action of bacteria. The action of both environments caused two opposing processes: unsealing the structure and deposition of corrosion products.

Effect of hydrodynamics and surface roughness on the electrochemical behaviour of carbon steel in CSG produced water

The influence of fluid flow, surface roughness and immersion time on the electrochemical behaviour of carbon steel in coal seam gas produced water under static and hydrodynamic conditions has been studied. The disc electrode surface morphology before and after the corrosion test was characterized using scanning electron microscopy (SEM). The corrosion product was examined using X-ray photoelectron spectroscopy (XPS) and X-ray diffractometry (XRD).The results show that the anodic current density increased with increasing surface roughness and consequently a decrease in corrosion surface resistance. Under dynamic flow conditions, the corrosion rate increased with increasing rotating speed due to the high mass transfer coefficient and formation of non-protective akaganeite β-FeO(OH) and goethite α-FeO(OH) corrosion scale at the electrode surface. The corrosion rate was lowest at 0rpm. The corrosion rate decreased in both static and dynamic conditions with increasing immersion time. The decrease in corrosion rate is attributed to the deposition of corrosion products on the electrode surface. SEM results revealed that the rougher surface exhibited a great tendency toward pitting corrosion.