Model Of Atmospheric Corrosion Research Articles

Time-variant fatigue reliability assessment of rib-to-deck welded joints using ANN-based methods

Environmental corrosion and vehicle load significantly influence the fatigue damage of steel bridges. To efficiently investigate the combined effect of stochastic vehicle load and environmental corrosion on the fatigue damage of welded joints of orthotropic steel decks (OSDs), an artificial neural network (ANN) assisted assessment framework is proposed. A stochastic fatigue vehicle load model and an atmospheric corrosion model are first adopted for probabilistic modeling of stress response of rib-to-deck (RD) welded joints. To reduce the calculation cost of large-scale finite element analyses (FEA) runs in probabilistic simulation, the relation is generated between the equivalent stress range and variables (i.e., vehicle loads and corrosion depth) using ANNs. The time-variant fatigue reliability, therefore, can be calculated using Monte Carlo (MC) simulations by considering the uncertainties of variables in limit-state functions. The efficiency and feasibility of the proposed framework are demonstrated with a steel bridge. Finally, parametric studies investigate the influence of traffic volume and corrosion on the time-variant fatigue reliability of RD welded joints.

Prediction of tempo-spatial patterns and exceedance probabilities of atmospheric corrosion of Q235 carbon steel across China.

To reduce the losses caused by the atmospheric corrosion of carbon steels, it is important to establish a prediction model to determine the corrosion rate of carbon steels in natural environments. In this study, a prediction model of atmospheric corrosion of Q235 carbon steel (PMACC-Q235) in China was established by coupling the mean impact value algorithm and back propagation artificial neural network. Tempo-spatial patterns of corrosion rates in five long-exposure time categories across China were analyzed. Ten main factors affecting the atmospheric corrosion of Q235 were identified. The corrosion rates in a single year were similar (approximately 30 μm/a) and larger than those for 2 (25.30 μm/a) and 3 years (21.66 μm/a). The spatial corrosion rates in the northwestern areas were primarily lower than those in southeastern coastal areas. This could be influenced by climatic factors, such as temperature, humidity, and precipitation. All corrosion rates reached the C2 level (>1.3 μm/a), and there was some possibility that they reached higher corrosion levels. The largest probability for the C3 level in all periods was an average of 0.91, and that for the C4 level was 0.83. Spatially, higher probabilities were mainly located in the southern area, especially in Hainan, located in the south and surrounded by sea. Corrosion rates largely varied among climatic zones, and mean corrosion rates in the tropical monsoon climate zone were the largest (average of three periods 33.39 μm/a). SO2 and soluble-dust fall had the largest impact on the variations in the corrosion rates among different climatic zones.

A service life model of metal ties embedded in the mortar joints of brick veneer walls with applications to reinforced concrete

The issue regarding the corrosion of steel ties connecting brick veneer to a structural backing is well documented. In this paper, the predicted corrosion rate and resulting service life estimates, produced by a time-stepped service life model developed in Visual Basic for EXCEL, for metal ties embedded in mortar, are compared with the empirically determined corrosion rates and service lives of 16 zinc galvanized tie specimens taken from 13 buildings located in 6 different Canadian cities. This tie service life model, coined the “Tie Service Life Predictor”, correlates the external environment of the building to the tie life. As with most corrosion models for steel embedded in concrete (or mortar), the model is broken into two distinct phases: corrosion initiation using Fick’s law of diffusion and corrosion propagation. By considering the mortar surrounding the tie as the tie’s atmosphere, the Tie Service Life Predictor characterizes the microenvironment (atmospheric conditions) surrounding the tie from the macroenvironment conditions. Once the atmospheric conditions were established, the ISOCORRAG atmospheric corrosion model could be used to predict the corrosion rate of zinc galvanized steel ties embedded in the mortar joints of the exterior wythe of brick veneer wall systems. The methods used to create the Tie Service Life Predictor could also be applied to service life estimation of reinforcing steel in concrete structures such as bridge decks and parking structures.

Effect of confined electrolyte volumes on galvanic corrosion kinetics in statically loaded materials

Abstract This work investigates the effects that the confined volume of atmospheric electrolytes has on the galvanic corrosion kinetics of a martensitic stainless steel alloy, UNS S13800, coupled with UNS A97075 in simulated atmospheric environments at relative humidity values that span the range of operational exposures. Restricted volumes found in thin films and droplets have been shown to control reduction reaction kinetics and are an ongoing challenge to characterize and standardize. This, along with the dynamic and high concentration of aggressive ions found in confined electrolytes, creates a unique corrosion system that requires a multifaceted approach to evaluate varied conditions, compare them with traditional measurements, and more accurately predict galvanic atmospheric corrosion. In this work, corrosion currents in galvanic couples were obtained under two environmental conditions: (1) bulk electrolytes, in a standardized test configuration, with chemistries relevant to atmospheric electrolytes; and (2) deliquesced droplets formed and equilibrated at a given temperature and relative humidity value. The corrosion currents for the same galvanic couple specimens were evaluated, using an atmospheric corrosion model, under a thin film electrolyte while statically loaded and unloaded, at two nominally different locations, e.g. Alexandria, VA, and Miami, FL, on the same date, using recorded weather conditions. The modeled corrosion currents were then compared with the currents obtained from the experimental conditions.

Performance evaluation of a reticulated shell with atmospheric corrosion damage

The study on damage evaluation induced by atmospheric corrosion of engineering structures has attracted more and more international concern over the past three decades. However, the effects of atmospheric corrosion on reticulated shells have not been systematically investigated. In this regard, the performance assessment of a reticulated shell subjected to atmospheric corrosion damage is actively conducted in this study. The atmospheric corrosion model of shell elements is first presented, and a refined exponential model for estimating the corrosion depth of steel materials is developed by using the pattern recognition technique. The sensitivity of stiffness matrix to element thickness is established by using Euler–Bernoulli beam element. The sensitivity of mass matrix to element thickness is developed based on lumped mass assumption. Then, the expression of natural frequency sensitivity to element thickness and mass is derived by considering the section loss induced by both the inner and outer surface corrosion. In addition, the explicit expression of frequency sensitivity to mass of spherical joints is also established in detail. The nonlinear static structural analysis is conducted to evaluate effects of atmospheric corrosion on the stress of structural elements. A real reticulated shell constructed in northern China is taken as the example structure to examine the feasibility of the proposed approach and to assess the potential damage caused by atmospheric corrosion to the structure.

Modeling of Atmospheric Corrosion in the Tropical Climate of Vietnam

The kinetics of corrosion losses of carbon steel, copper, and zinc in the continental and coastal areas of Vietnam is studied by in situ testing. The dominant climate and aerochemical atmospheric factors are revealed with respect to the metals tested in different periods of their exposure. The mathematical models that characterize the relationship between the time of wetness of metal surface, atmospheric pollution, and corrosion rate are developed. Based on power law model M = At k , the values of constants A and k are calculated for each metal and test site, where parameter A characterizes corrosion losses of metal for the first year of exposure and k denotes the protective properties of a layer of corrosion products.

Comparing Modeled and Experimental Accelerated Corrosion Tests on Steel

Four different accelerated corrosion tests on steel are simulated with a Dynamic Electrolyte Film Corrosion model. Based on the time dependent temperature and humidity, combined with the presence of hygroscopic salts, a time dependent electrolyte thickness is calculated. At every timestep, the modeled film thickness dictates the corrosion current. Focussing on the thickness predictions, an elementary corrosion model is adopted to enable the corrosion depth estimations. The trends of the simulated corrosion depths are compared with experimental data obtained with an electrical resistance corrosion sensing system, demonstrating the importance of the electrolyte thickness and composition for a thorough understanding and modeling of atmospheric corrosion on steel.

Development of the Atmospheric Corrosion Model of Nickel-Coated Carbon Reinforced Aluminum (Al/C/50f) MMCs

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The role of chloride ion on the atmospheric corrosion of steel and corrosion resistance of Sn-bearing steel

In order to clarify the role of chloride ion on the atmospheric corrosion of steels, the minute anode chamber simulating local anode sites on steels was set up, and the pH change was measured. The pH was affected by the chloride concentration, and decreased to 1.5 with the formation of β-FeOOH. The role of chloride ion on the corrosion is discussed from the viewpoint of solubility and hydrolysis of Fe3+-species. An atmospheric corrosion model under high chloride content environments is proposed. Based on the model, it was found that Sn-bearing steel exhibits the superior atmospheric corrosion resistance.

Towards the development of a corrosion map for Abu Dhabi

AbstractInfrastructure development in the United Arab Emirates continues to escalate, yet very few corrosion studies have been performed in the region. In a step to address this situation, this paper reports on a study of zinc and steel corrosion and salt deposition rates at five sites in the Emirate of Abu Dhabi. The sites are classified as either urban/marine, marine, inland or mountainous. The study found that zinc corrosion rates range from 15 µm/year on the coast to 0.6 µm/year inland, while steel corrosion rates are 56 and 10 µm/year, respectively, at the same locations. While the salt deposition rate ranges from 5 to 18 mg/m2/day, it is not directly related to distance from the coast. Although the salt deposition rates observed are consistent with those at locations at similar latitudes, the corrosion rates are higher than in locations with comparable salt deposition rates. However, when the data were analysed along with relevant local meteorological data, it was found to be consistent with the basic assumptions of the holistic model of atmospheric corrosion developed by Cole et al. In particular, it is suggested that the relatively high corrosion rates observed here are associated with a greater accumulation of salt, which can occur in Abu Dhabi because rainfall, and thus rain washing, is extremely low compared to similar exposure locations in Australia and South‐East Asia.

The atmospheric corrosion of zinc: The effects of salt concentration, droplet size and droplet shape

The influence of droplet characteristics on the atmospheric corrosion of zinc was investigated using a multi-microelectrode approach. Arrays of close-packed zinc wires, 500 μm in diameter, were coupled such that the net anodic and cathodic current flowing through each electrode interface was measured as a function of time. Droplets in the range of 1–10 μL placed onto the array showed that electrochemical fields are immediately established and can remain unaltered for significant periods of time. The total charge passed was found to be almost identical for 0.6 M NaCl droplets of varying size when compensating for the electrolyte–zinc contact area, however significant differences in current exchange were observed when varying electrolyte concentration. In contrast to studies on other metals, the highest rates of zinc corrosion, as measured by the microelectrode array, did not occur during drying cycles. It was observed that the initial wetting and subsequent holding at high relative humidity led to the highest measured currents. Corrosion damage during drying cycles, however, appears to be enhanced for large droplets with high contact angle and increased electrolyte concentration. The importance of these observations to the modeling of atmospheric corrosion has been discussed and future developments of the technique are outlined.

Optimising aircraft wash intervals from maintenance records

Washing aircraft is a routine maintenance chore that is intended to reduce corrosion damage by removing corrodents. However, this exercise incurs costs that are substantial when applied to a fleet. The United States Air Force (USAF) algorithm for setting wash intervals was based on an environmental severity index and an implied set of economic assumptions. A novel approach is described for setting the economically optimal wash interval based on maintenance records, an atmospheric corrosion model, explicit economic parameters and corrosivity measurements. The maintenance records required are the number of man hours applied to repairing corrosion related damage and the number of months since the last repair. The atmospheric corrosion model assumed a bilogarithmic or power law relationship between cumulative damage and exposure time. The economic parameters considered are the cost per wash, the cost of unavailability during a wash and the charge rate for maintenance manpower. It is assumed that atmospheric severity increases corrosion damage, whereas washing decreases it. This approach requires a measure of atmospheric corrosivity that is not restricted to any particular method as long as the processing of maintenance data and the prediction of the optimal wash interval uses the same method.

Holistic model for atmospheric corrosion Part 7 – Cleaning of salt from metal surfaces

This is the seventh paper outlining a holistic model of atmospheric corrosion. Previous papers have outlined how airborne salinity can be estimated at any given location, how salt deposition onto a surface can be modelled and what forms moisture can take on a plate surface. The present paper develops a model for rain induced cleaning of deposited aerosols from metal surfaces. The individual phenomena of splash and wash off are modelled, and then the effect of these processes on salt retention is discussed. The results of the models are compared with data from field exposures and laboratory tests. Simplified rules to allow the process to be incorporated into the holistic model framework are proposed.

GILDES Model Studies of Aqueous Chemistry: VI. Initial - and -Induced Atmospheric Corrosion of Copper

GILDES, a computer-based model of atmospheric corrosion, has been used to simulate copper exposed at room temperature to 200 ppb in combination with either or at different concentrations. The GILDES model involves the five most important regimes in atmospheric corrosion (gas, liquid, deposition, electrodic, and surface) and includes 27 aqueous species and more than 60 aqueous reactions. Under these exposure conditions copper forms cuprite and various copper sulfates in both and mixtures, and copper hydroxynitrate in after an incubation time of 4 h. Among these experimental observations the GILDES model correctly predicts the formation of copper sulfate (in both and mixtures) and copper hydroxynitrate . It is furthermore able to predict the formation rate of copper sulfate in mixtures, but not the formation rate of copper sulfate and copper hydroxynitrate in mixtures.

Attachment Efficiencies of Salt Aerosols onto Infrastructure and Implications for Atmospheric Corrosion

To support a holistic approach to the modeling of atmospheric corrosion, an experimental program was undertaken to delineate the effects of relative humidity, wind speed, and infrastructure surface chemistry on the efficiency of salt aerosol retention. The fundamental adhesion between a salt crystal and a metal oxide surface was studied using colloid probe atomic force microscopy. The magnitude of adhesion was dependant upon the probe dimensions, surface chemistry, and relative humidity. Parallel experiments investigated the removal of salt particles/aerosols from both clean hydrophilic and hydrophobized glass slide surfaces in a wind tunnel. The efficiency of the removal of particulates from glass surfaces was found to be a function of relative humidity, and the influence of humidity and wind velocity appeared to be magnified by increasing the glass hydrophobicity. Furthermore, alterations in the glass surface chemistry led to notable differences in the size and distribution of adsorbed salts. The experimentally determined salt retention efficiencies enable current holistic lifetime prediction models to be updated and expanded, and provides insight into the ability of surface chemistry to control aerosol retention processes and thus atmospheric corrosion. © 2005 The Electrochemical Society. All rights reserved.

Experimental studies of salts removal from metal surfaces by wind and rain

This paper outlines an experimental programme aimed at determining the mechanisms of salt removal from metallic surfaces by wind and rain. The paper provides data and process understanding that will be integrated into a holistic model of atmospheric corrosion. Experiments are reported in which fine salt crystals were deposited either wet (as fine droplets of seawater) or dry onto a surface. The surfaces were then placed in a wind tunnel and salt loss was determined as a function of wind speed. In another experiment, the motion of simulated raindrops falling onto metal plates was determined. Finally, in a third series of experiments, video footage of simulated rain on metal surfaces was studied in order to determine both the subsequent motion of rain and its cleaning efficiency. The efficiency of surface cleaning by wind and rain, as determined by these experiments, was then related to Australian climatic conditions. A future paper will present mathematical models of the processes defined in this paper.

Holistic model for atmospheric corrosion Part 6 – From wet aerosol to salt deposit

This paper is the sixth paper outlining a holistic model of atmospheric corrosion. Previous papers outline how airborne salinity could be estimated at any given location and how the deposition onto a surface could be modelled. This paper investigates the initial reactions of raindrops or deposited marine aerosols on metal surfaces (zinc, galvanised steel, aluminium and gold). It combines short term field exposures with a series of controlled laboratory experiments. Surface changes to the metal upon field exposure are characterised by the nature and distribution of corrosion nodules, oxide films and retained salts. Eleven distinct forms of surface change are observed. The conditions promoting each pattern of surface changes were estimated by comparison with laboratory tests with a variety of deposition modes. Laboratory tests included deposition of saline droplets in three size ranges. A strategy to use the results in a holistic model of corrosion is proposed.

Holistic model for atmospheric corrosion Part 5 – Factors controlling deposition of salt aerosol on candles, plates and buildings

This paper is the fifth in a series of papers outlining a holistic model of atmospheric corrosion. Previous papers have outlined how the airborne salinity could be estimated at any given location. This paper presents a theoretical analysis of aerosol/particulate deposition, in conjunction with computational fluid dynamics (CFD) studies. Theoretical and CFD studies address whether salt aerosol/particulate deposition is controlled by mean winds, wind turbulence or Brownian motion (deposition of salt via rain/fog etc. is not considered in this paper). Analysis indicates that deposition due to wind turbulence is the dominant mechanism for marine aerosol, and that other deposition modes can be effectively ignored. Given this, further studies are presented for salt candles, plates and buildings. From these studies, approximations are derived so that salt deposition on exposure plates and on buildings can be estimated from measurements from ISO salt candles.

Artificial neural network modeling of atmospheric corrosion in the MICAT project

This paper presents an Artificial Neural Network(ANN)-based solution methodology for modeling atmospheric corrosion processes from observed experimental values, and an ANN model developed using the cited methodology for the prediction of the corrosion rate of carbon steel in the context of the Iberoamerican Corrosion Map (MICAT) Project, which includes seventy-two test sites in fourteen countries throughout Iberoamerica. The ANN model exhibited superior performance in terms of goodness of fit (sum of square errors) and residual distributions when compared against a classical regression model also developed in the context of this study, and is expected to provide reasonable corrosion rates for a variety of climatological and pollution conditions. Furthermore, the proposed methodology holds promise to be an effective and efficient tool for the construction of analytical models associated with corrosion processes of other metals in the context of the MICAT project, and, in general, in the modeling of corrosion phenomena from experimental data.

Development of regional corrosion maps for galvanized steel by linking the RADM engineering model with an atmospheric corrosion model

Abstract Annual corrosion rates for galvanized steel standard panels were estimated for eastern North America and part of southern Canada using the Regional Acid Deposition Model Engineering Model Model (ACM). The galvanized steel ACM examines the contributions of wet and dry deposition, including anthropogenic and naturally occurring atmospheric species to galvanized steel structure corrosion. The results show agreement between model-predicted and field-measured annual corrosion rates of galvanized steel panel except for an exposure site located in up-state New York. Further comparison of corrosion rates showed some spatial disagreement of the relative contributions to the individual corrosion processes, particularly for the New York site. In addition, RADM EM MM-4 was used to predict the change in ambient sulfur (S) concentrations and hydrogen ion deposition from a hypothetical uniform 50°, reduction in S emissions. Using the ACM, the effects of the emission reduction on the annually estimated corrosion rates were modeled. The results show a beneficial reduction in regional corrosion rates estimated annually. However, due to nonlinearities associated with wet and dry deposition, the corrosion rates decline in a less than 1:1 proportion to the emissions reduction.