Corrosion Penetration Depth Research Articles

Corrosion behavior of Ce-doped Ni-10Cu-11Fe-6Al (wt%) inert anode in molten CaCl2 salt

In this research the effect of cerium dopingon corrosion behavior of Ni-10Cu-11Fe-6Al (wt%) alloy as a novel inert anode in titanium electrolytic production was investigated. The samples, including un-doped and Ce-doped nickel-based alloys, were prepared using vacuum induction melting (VIM) process and then exposed to the electrolysis in molten calcium chloride at 900 °C at −1.6 V versus graphite reference electrode for different immersion time. The surface and cross-section of the samples were characterized using scanning electron microscopy (SEM), and their electrochemical behavior was investigated by electrochemical impedance spectroscopy (EIS). The results show that the un-doped samples have greater number of voids and porosities as compared to that of the 0.0064 wt% Ce-doped samples (as the optimum content of cerium in the alloy). Thus, the nickel-based alloy becomes less sensitive to the pitting by addition of cerium. The corrosion penetration depth reaches about 244 μm after 16 h of electrolysis in the un-doped sample, while was approximately 103 μm for the 0.0064 wt% Ce-doped sample, which is an indication that the corrosion penetration depth decreases by adding small amounts of Ce.

Effect of Si on Hot Corrosion Resistance of CoCrAlY Coating

Abstract The CoCrAlSiY coating was prepared by HVOF (high velocity oxygen fuel) method. The hot corrosion resistance of the CoCrAlSiY coating with different Si concentrations (0wt%, 2wt% and 5wt%) at 900 °C was discussed by hot salt coating method with a mixed salt of 75wt% Na2SO4+25wt% NaCl. The results show that the average corrosion penetration depth of the coating increases with the rising of temperature, while the increasing of Si concentration decreases the average corrosion penetration depth of the coating. Furthermore, CrSi, a high melting point metal silicide, is generated inside the CoCrAlSiY corrosion coating. Thus it is beneficial for improving the corrosion resistance of the coating.

Застосування електроіскрової обробки сталевих поверхонь для підвищення якості лакофарбових покриттів

У роботі використовувався електроіскровий метод підготовки сталі електричними шліфувальними машинами із застосуванням технологічних рідин, які містять синергічні суміші ПАР і інгібіторів. Також проводилась обробка оцинкованими щітками, під час якої цинк переходив на поверхню металу і створював осередки протекторів. Показано, що поєднання протекторного захисту з інгібіторами і лакофарбовими покриттями характеризується нададетивністю. За рахунок цього досягається підвищений ефект інгібування корозії сталі, підвищення адгезії і захистних властивостей лакофарбових покриттів.

The Durability of a Concrete Sewer Pipeline under Deterioration by Sulphate and Chloride Corrosion

In the article an issue of corrosion impact both sulphate and chloride on the reliability index was solved by analytical methods. The pipeline was located in a homogenic soil backfill under communication load. The depth of corrosion penetration was estimated by selection of the maximum length of cracks. As a result of deterioration zone appeared to be a function of time in exploitation according to average environmental concentration which can initialise a percent of chemical and mechanical degradation of concrete. The work shows also the complete analytical way which help to assess the safety level of sewer pipelines what can be introduced to geographic information systems.

Numerical assessment of non-uniform corrosion scenarios of rebar in concrete exposed to natural chloride environment

Corrosion of embedded rebars is a classical deterioration mechanism that remains as one of the most significant problems limiting the service life of concrete structures exposed to chloride-laden environments. The primary objective of this study is to propose and verify a numerical framework that can efficiently quantify non-uniform corrosion penetration depth along the perimeter of the rebar in concrete exposed to chloride environment. This framework investigates the corrosion process during both the corrosion initiation and propagation phases by exploring the effects of not only the rebar existence but also its sizes and locations. The corrosion initiation phase is examined through a comprehensive chloride ingress model that identifies the most important parameters that influence the intrusion of chlorides into RC. The corrosion propagation phase is studied based on a decisive parameter, namely, the corrosion rate. In addition, the framework evaluates the non-uniform corrosion states that correspond to two scenarios of corrosion penetration depth: corrosion of segment of the rebar and uneven corrosion along the rebar perimeter. Numerical solution shows that, in general, chloride build-up along the perimeter of the corner bar is not only faster but also higher than that of the middle bar. Moreover, for the given values of cover thickness and water-to-binder ratio, time-to-corrosion initiation for the corner bar is faster than that for the middle bar. Furthermore, the larger the rebar, in general, the bigger the obstruction, and therefore, the higher the chloride build-up. Qualitative comparisons of the evaluated non-uniform corrosion scenarios with the variety of available laboratory and field data show good agreement.

Non-uniform corrosion states of rebar in concrete under chloride environment

This study proposes and verifies a numerical framework that can efficiently quantify non-uniform corrosion penetration depth along the perimeter of the rebar in concrete exposed to chloride environment. Moreover, this framework considers the effects of rebar size and location on the process of chloride ingress into concrete and evaluates the non-uniform corrosion states that correspond to two scenarios of corrosion penetration depth: corrosion of segment of the rebar and uneven corrosion along the rebar perimeter. Qualitative comparisons of the evaluated non-uniform corrosion states with the variety of available laboratory and field data show good agreement.

Intergranular Corrosion Penetration in an Al-Mg Alloy as a Function of Electrochemical and Metallurgical Conditions

An experimental and modeling study of factors influencing intergranular corrosion (IGC) penetration depth into an Al-Mg alloy, AA5083 (UNS A95083), is presented. Potentiostatic tests over a range of potentials in 0.6 M sodium chloride (NaCl) solution were conducted on longitudinal by long transverse (LT), long transverse by short transverse (ST), and longitudinal by short transverse (LS) surfaces of sensitized AA5083. The IGC penetration rate was found to depend on applied potential, degree of sensitization (DoS), exposure time, and propagation direction relative to the rolling direction. Statistical IGC depth distributions were analyzed and served as inputs for a phenomenological model to estimate IGC damage progression for AA5083 during exposure to 0.6 M NaCl solution at pH 8.3. This model was validated by comparing the model predicted and experimental depths for the 100°C sensitization condition. Extension of this combined experimental and modeling approach to the 80°C sensitization demonstrated that s...

Corrosion resistance of zinc-coated structured sheet metals

The purpose of this study is to characterise the corrosion behaviour of zinc-coated sheet metals after a structuring process using the salt spray test. The investigated structured material is manufactured by hydroforming and has a periodic hexagonal geometry. The corrosion behaviour has been evaluated by estimating the development of the corrosion area and penetration depth. The results of the investigation show that the corrosion area is larger on the smooth sheet than on the structured sheet. The difference between the structured and smooth sheets is negligible with increasing exposure time. Furthermore, the reasons for the different corrosion behaviours are discussed.

Intergranular Corrosion Penetration in AA5083 (UNS # A95083) as a Function of Electrochemical and Metallurgical Conditions

A coordinated experimental and modeling study of selected factors influencing intergranular corrosion (IGC) penetration depth into AA5083 is presented. Potentiostatic tests at -0.73 VSCE in 0.6 M NaCl solution were conducted on LT, ST, and LS surfaces of sensitized AA5083. The IGC penetration rate was found to depend on applied potential, degree of sensitization (DoS), exposure time, and propagation direction relative to the rolling direction. Depths of IGC penetration were characterized through metallographic techniques, microscopy, and image analyses. The results were analyzed to describe the IGC depth distributions and to serve as input data for a set of descriptive models that can estimate IGC damage progression for AA5083 during exposure to 0.6 M NaCl at pH 8.3. This set of descriptive models was validated with 94% accuracy for 100oC sensitization. Extension of this combined experimental and modeling approach to 80oC sensitization demonstrated that sensitization temperature is another significant factor.

Analytical Model for Corrosion Penetration Depth at Cover Cracking in RC Structures

Corrosion products which occupy much greater volume accumulate, and generate expansive pressures on the surrounding concrete. The pressure builds up and eventually leads to the cover cracking of the structures. The cracking accelerates further corrosion and leads to the loss of the bond strength and the load carrying capacity. Corrosion cracking would reveal the reducing of the residual service life of the corrosion-affected structures. In this paper, an analytical model is proposed to predict the critical corrosion penetration at cover cracking in RC structures based on the crack process. An attempt has been made to develop the model by considering material properties of the surrounding concrete and expansive corrosion products. The problem is established as a boundary-value problem and the governing equations are expressed in terms of the radial displacement. The analytical predictions of the proposed model have also been in agreement with the available experimental data.

Effect of Endgrain Attack on Corrosion of 18Cr-10Ni Austenitic Stainless Steel in Simulated Dissolver Liquor

The exposed endgrain of austenitic stainless steels displays significantly inferior corrosion resistance toward the rolling direction in nitric acid solutions. Endgrain attack is often accompanied by preferential localised corrosion which produces features similar to pitting corrosion. From the viewpoint of average corrosion rate and penetration depth the effect of endgrain attack on the corrosion of 18Cr-10Ni austenitic stainless was investigated in simulated dissolver liquor under non-boiling conditions. The average corrosion rate of coupons was evaluated as a function of endgrain ratio to total surface area. In addition the effect of orientation with respect to the rolling direction was measured directly by observing the dimensional change of holes drilled into coupons. It was found that the proportion of exposed endgrain affected the coupon corrosion rate. From the hole growth measurements it was found that the average corrosion rate in the rolling direction was 2.3 mm/yr approximately 1.5 times higher than that of the vertical one on the surface. From sections the maximum extent of pitting penetration into the endgrain was estimated to be approximately 8.8 mm/yr.

Corrosion penetration monitoring of advanced ceramics in hot aqueous fluids

Advanced ceramics are considered as components in energy related systems, because they are known to be strong, wear and corrosion resistant in many environments, even at temperatures well exceeding 1000 °C. However, the presence of additives or impurities in important ceramics, for example those based on Silicon Nitride (Si3N4) or Al2O3 makes them vulnerable to the corrosion by hot aqueous fluids. The temperatures in this type of corrosion range from several tens of centigrade to hydrothermal conditions above 100 °C. The corrosion processes in such media depend on both pH and temperature and include often partial leaching of the ceramics, which cannot be monitored easily by classical gravimetric or electrochemical methods. Successful corrosion penetration depth monitoring by polarized reflected light optical microscopy (color changes), Micro Raman Spectroscopy (luminescence changes) and SEM (porosity changes) will be outlined. The corrosion process and its kinetics are monitored best by microanalysis of cross sections, Raman spectroscopy and eluate chemistry changes in addition to mass changes. Direct cross-calibrations between corrosion penetration and mechanical strength is only possible for severe corrosion. The methods outlined should be applicable to any ceramics corrosion process with partial leaching by fluids, melts or slags.

Corrosion of silicon nitride in aqueous acidic solutions: penetration monitoring

The degradation behaviour of silicon nitride in aqueous acidic solutions under steady state conditions was studied at 90 C and different flow rates. Two different compositions were chosen: Si3N4+4 wt.% Al2O3+6% Y2O3 (SN0) and Si3N4+2.4 wt.% MgAl2O4+1.3 wt.% Y2O3 (SN1). Corrosion was monitored by mass change, eluate chemistry, microstructure of the penetrated zone and fracture strength. The main corrosion mechanism is the leaching of the grain boundary phases. The penetrated depths consists of at least two zones with an outer layer, which is characterised by a complete or at least extensive removal of the total grain boundary phase and an inner zone, where pure silica, from which Y and Al have been leached, persists. The rates of dissolution of Al, Y and Si ions decreased with corrosion time. The fracture strength decreased with increasing degree of dissolution of the grain boundary phase. Changes in the chemistry of the grain boundary phases result in strong changes of corrosion resistance. Successful corrosion penetration depth monitoring can be done by polarised reflected light optical microscopy (colour changes), Micro Raman Spectroscopy (luminescence changes) and SEM (porosity changes). The corrosion process and its kinetics are evidenced best by microanalysis of cross sections, Raman spectroscopy and the eluate chemistry changes in addition to mass changes. # 2003 Elsevier Science Ltd. All rights reserved.

Corrosion behavior of irradiated oxide fuel pellets in high temperature water

In order to elucidate fuel wash-out behavior after the degraded secondary failure of BWR fuel rods, corrosion experiments in high temperature and high pressure water of 340°C and 15 MPa were conducted for UO2 and UO2−10 wt%Gd2O3 fuel pellets with different grain sizes, which had been irradiated in a commercial BWR or a test reactor (burnup: 32–34 GWd/tU). The fuel corrosion was characterized by the occurrence of microcracks along the grain boundaries due to preferential U4O9 formation, and became noticeable in the oxygenated water of more than several ppm dissolved oxygen concentration. The grain boundary penetration depths for the irradiated pellets were approximately equivalent to, or somewhat deeper than the values for previous unirradiated pellets reported by the present authors. Consequently, fuel irradiation, i.e., accumulation of fission products had no significant effect o n the fuel corrosion. Enlarging grain size and 10 wt% Gd2O3 doping distinctly improved the corrosion resistance. The 85Kr release into the hot water, which had been accumulated in the grain boundaries during base irradiation, increased linearly with corrosion penetration depth.

Impact of Thermal Loading on Waste Package Material Performance

AbstractThis report focuses on the prediction of materials performance for the carbon steel corrosion-allowance container as a function of thermal loading for the potential repository at Yucca Mountain. Low, intermediate and high thermal loads were evaluated as to their performance given assumptions regarding the temperature and humidity changes with time and the resultant depth of corrosion penetration. The reference case involved a kinetic relation for corrosion that was utilized in a sensitivity analysis to examine the impacts of time exponent, pitting, and microbiologically-influenced corrosion. As a result of this study, the high thermal load appears to offer the best corrosion performance. However, other factors must be considered in making the final thermal loading decision.

Evaluation of corrosion failure by extreme value statistics.

Recent advances in the field of corrosion failure evaluation by the extreme value statistics have been reviewed. Historical background of the extreme value statistics, and recent developments in the theory and application to corrosion are described. The extreme value distribution contains three asymptotic distributions which are derived from the initial distributions, but the first type for the maximum value, i.e., the Gumbel distribution and the third type for the minimum value, i.e., the Weibull distribution are mainly used for evaluating the maximum depth of corrosion penetration and the minimum time for corrosion failure, respectively. It is emphasized that the parameter estimation could be accomplished simply by using a minimum variance linear unbiased estimator (MVLUE) method which has been refined recently. Several problems in applying the MVLUE method were discussed with referring experiences in the data analysis.

Grain boundary segregation in austenitic stainless steels and its effect on intergranular corrosion and stress corrosion cracking

This paper reports a study of grain boundary segregation, intergranular corrosion, and intergranular stress corrosion cracking in austenitic stainless steels. The results show that phosphorus, nitrogen, and sulfur all segregate to grain boundaries in these materials and that they can affect one another's segregation through site compctition. In particular, the results demonstrate that phosphorus segregation can be lowered by the presence of nitrogen and sulfur in the steel. Also, if manganese is present in the steel, sulfur segregation will be greatly decreased as a result of formation of manganese sulfides. Phosphorus, sulfur, and nitrogen will not initiate intergranular corrosion in the modified Strauss test, although if corrosion is initiated by chromium depletion, these elements might enhance the corrosion process. Phosphorus segregation does enhance corrosion in the Huey test, even in steels that have not undergone grain boundary chromium depletion, although there does not appear to be a precise correlation between the depth of corrosion penetration and phosphorus segregation. Intergranular stress corrosion cracking in 288 °C water at a pH of 2.5 and electrochemical potential of OVSHE can occur in these steels even in the absence of chromium depletion if sulfur is present on the grain boundaries. Phosphorus segregation appears to have very little effect.

A Comparison between Grain Boundary Chromium Depletion in Austenitic Stainless Steel and Corrosion in the Modified Strauss Test

Abstract This paper reports a detailed comparison between an analytical electron microscopy (AEM) study of the chromium depletion process around grain boundary carbides in an austenitic stainless steel (SS) and the corrosion results for the same steel tested in the modified Strauss test. The comparison shows that chromium depletion is the primary cause for attack in this test. The occurrence of corrosion, shape of the corroded region at the grain boundary, length of attack along a boundary, and depth of corrosion penetration into the sample can all be explained in terms of the chromium depletion detected by AEM. The only disagreement is in the width of the corroded region at the grain boundary. It is always wider than that of the depleted material.

Fatigue Tests of 8‐yr Weathered A588 Steel Weldment

Fatigue tests of 62 specimens determined the effect of 3‐year, alternate, and 8‐year weathering on the number of cycles to failure of a transverse stiffener detail fabricated from ASTM A588 weathering steel. These three weathering conditions reduced the mean losses in fatigue life by 42%, 42% and 54%, respectively, as compared to the life of the nonweathered control specimens. The loss in life came at the expense of the number of cycles needed to initiate fatigue cracks and is attributed to rust pitting. The progressive nature of the loss in life with length of exposure time is similar to that reported in the literature for corrosion penetration and pit depth.

65-35黄銅の引張強さにおよぼす予腐食の影響

The effect of pre-exposure on the apparent tensile strength of annealed and/or cold rolled specimens of 65%Cu-35%Zn brass, which were pre-exposed to 2.5N ammoniacal solutions containing 0-40g/l Cu for 3hr at room temperature, was examined as the parameters with respect to chemical composition of solutions, pre-strain, grain size and cold reduction.The results obtained are as follows;(1) The decrease of tensile strength of both annealed and cold rolled specimens due to preexposure depended largely on the chemical composition of solutions, and the maximum decrease was found when thick black tarnished layer was formed.(2) The apparent tensile strength of annealed specimen was exceedingly decreased when the specimen was pre-strained at yield point.(3) The apparent tensile strength of cold rolled specimen increased with pre-straining.(4) The decrease of apparent tensile strength due to pre-exposure was nearly proportional to depth of corrosion penetration.