Field Exposure Test Research Articles

Novel Understanding of the Formation and Protectiveness of Corrosion Product Film on Ca–Sb–Cr Weathering Steel

The addition of Ca and Sb in Cr‐bearing steel presents improved corrosion resistance during the field exposure test in a marine atmosphere environment. Through local hydrolysis reactions, Ca and Sb can form CaO, Sb2O3, and Sb2O5 to prevent the intrusion Cl− into the corrosion product film, which improves the protectiveness of the corrosion product film and reduces the corrosion rate. The formation of CaCl2 decreases the relative content of β‐FeOOH and makes the corrosion product film more stable. Due to the inhibition of Sb on the local acidification of corrosion product film, Ca and Cr are able to bond with more hydroxide for generating the corresponding oxides and improving the corrosion resistance of Cr‐bearing steel.

Effect of barnacle on the cathodic protection of high-strength steel and its potential risk related to hydrogen permeation

The cathodic protection efficiency and hydrogen permeation behaviour of high-strength steel with barnacle adhesion in the tidal zone were studied using field exposure and laboratory simulation tests for 2 years. Because of the shielding effect, barnacles can lead to an uneven calcareous deposition, a flatter morphology and a higher protection efficiency of steel. By contrast, because of the higher hydrogen permeation current at the edge of the barnacle adhesion area (caused by a higher hydrogen evolution rate), barnacle adhesion can promote hydrogen permeation. A mechanism was proposed to explain the observed phenomenon, and its effect on service safety was analysed.

Dynamic Marine Atmospheric Corrosion Behavior of AZ91 Mg Alloy Sailing from Yellow Sea to Western Pacific Ocean.

In this work, the dynamic marine atmospheric corrosion behavior of AZ91 Mg alloy sailing from Yellow Sea to Western Pacific Ocean was studied. The corrosion rates were measured using the weight loss method. The microstructure, phase, and chemical composition of corroded samples were investigated by SEM, EDS, XRD, and XPS. The results show that the evolution of corrosion rates of AZ91 Mg alloy was divided into three stages: rapidly increasing during the first 3 months, then remaining stable for the next three months, and finally decreasing after 6 months. The annual corrosion rate of Mg alloy reached 32.50 μm/y after exposure for 12 months in a dynamic marine atmospheric environment, which was several times higher than that of the static field exposure tests. AZ91 magnesium alloy was mainly subjected to localized corrosion with more destructiveness to Mg parts, which is mainly due to the synergistic effect of high relative humidity, the high deposition rate of chloride ion, sulfur dioxide acidic gas produced by fuel combustion, and rapid temperature changes caused by the alternating changes in longitude and latitude during navigation. As the exposure time increased, the corrosion pits gradually increased and deepened. The maximum depth of the corrosion pit was 197 μm after 12 months of exposure, which is almost 6 times the average corrosion depth. This study provides scientific data support for the application of magnesium alloys in shipborne aircraft and electronic equipment. The results could provide guidance for the design of new magnesium alloys and development of anti-corrosion technologies.

Study on hydrogen permeation and stress corrosion cracking behaviors of AISI 4135 high-strength steel with macrofouling adhesion in marine immersion zone

A field exposure test was set up to study the effect of macrofouling adhesion on hydrogen permeation and stress corrosion cracking (SCC) behaviors of a high-strength steel in marine immersion zone, and the results were further verified by laboratory electrochemical simulation tests. The results indicated that the crevices formed by macrofouling adhesion can promote localized corrosion pits and change the local chemical environment. More severe localized corrosion can increase the hydrogen permeation current density and promote the SCC of high-strength steel. As a comparison, the hydrogen permeation current density of steel under cathodic protection state was slightly decreased owing to the shielding effect of macrofouling.

Analysis of Beibu Gulf tidal zone exposure on properties of carbon steel

Marine tidal zone is a corrosive environment that has a negative impact on carbon steel. This research investigates the change of mechanical properties and corrosion behaviour of carbon steel specimens subjected to field exposure test and simulation test for 12 and 6 months, respectively. The corrosion behaviour of carbon steel exposed to real marine tidal zone and simulation environment was discussed through morphological observation and corrosion kinetics analysis, in order to reveal the essential reason for the degradation of its mechanical properties. Then the tensile test was performed on the corroded specimens and true stress–strain curves were obtained. In addition, regression equations were derived for the mechanical properties as a function of the degree of corrosion degradation and a constitutive model with time factor for corroded carbon steel is proposed.

Monitoring Atmospheric Corrosion of Carbon Steel Under Controlled Electrolyte Droplet Distributions

Field exposure testing and accelerated corrosion testing are two common approaches applied in the industry to assess the atmospheric corrosion rate of a specific material, both relying on visual inspection and weight change of the specimen. Field exposure testing occurs under natural atmospheric conditions but requires exposure times spanning decades, whereas accelerated corrosion testing shortens the exposure time to weeks; however, the connection between the natural environment and accelerated corrosion chamber conditions remains unresolved. Efforts have been made to correlate accelerated corrosion results with those obtained in field exposure based on weight loss, both qualitatively and quantitatively, primarily empirically and limited to small datasets.This work examines the link between modified field exposure testing and the environment from the electrolyte perspective, under controlled laboratory conditions. In-situ monitoring and analysis of corrosion rate, electrolyte condition, and environment are demonstrated to be feasible, and the effect of NaCl concentration and droplet distribution on the atmospheric corrosion rate of carbon steel has been addressed.This work proposes a setup wherein multiple droplet-based conditions are created, and corrosion kinetics are actively monitored using the electrical resistance method. The sample surface is simultaneously monitored with an optical microscope, through which both droplet distribution evolution and corrosion product formation can be visualized.

Optimizing microstructure for enhanced atmospheric corrosion resistance of a novel Ni–Mo weathering steel: A field exposure study in Thailand's tropical marine environment

This study compares the weathering performance of steel with three microstructures: ferrite, ferrite + bainite, and bainite. The rolling and cooling processes of a novel and cost-effective Ni–Mo weathering steel (WS) were manipulated to achieve these microstructures. Validation of these microstructures was performed through field exposure tests in Trat, Thailand, representing a typical tropical marine atmospheric environment. The bainitic steel exhibited better weathering resistance. After 12-month of exposure, the corrosion rates for ferritic + bainite and bainitic steels were 105.6 % and 97.9 % respectively, compared to ferritic steel. The variation in corrosion rates confirm that modifying the microstructure, with emphases on bainite, improves the WSs' resistance to atmospheric corrosion. Changes in corrosion rate mainly depend on the rust layer's adherence. Interestingly, α-FeOOH predominantly characterizes the rust layer on the skyward side of the samples following 12-month of exposure, while the earthward side is mainly composed of Fe3O4/γ-Fe2O3.

Service life prediction and time-variant reliability of reinforced concrete structures in harsh marine environment considering multiple factors: A case study for Qingdao Bay Bridge

Chloride attack is the primary cause of performance deterioration and life attenuation of reinforced concrete (RC) structures in marine environments. In an attempt to accurately predict the reliability and service life of RC structures under the co-effects of multiple factors, a comprehensively modified chloride-transport-based model is proposed in this paper. Based on Fick's second law, a multifactor integrated deterministic chloride transport model is developed considering the time dependence, concrete mix proportion, chloride binding capacity, freeze–thaw cycles, sustained load, temperature, humidity and concrete deterioration. Based on extensive literature review combined with the results of multitudinous long-term field exposure tests used in the durability design of Hong Kong-Zhuhai-Macao Bridge and Shenzhen-Zhongshan Bridge, the probability distribution types and parameter values of the governing variables are determined. Taking Qingdao Bay Bridge as an example, the time-variant reliability index, failure probability and reliability-index-based corrosion initiation are determined by using the equivalent normalization method (JC method) and Monte Carlo simulation technique for different environmental zones including atmospheric/splash/tidal/submerged zones. The sensitivity of the reliability index to the control variables and the effects of age index, chloride binding capacity, numbers of freeze–thaw cycles, stress level and concrete deterioration on the reliability index are quantitatively investigated. The results show that the time-variant reliability of different environmental zones is sequenced as: atmospheric zone > submerged zone > tidal zone > splash zone; the sensitivity of reliability to the governing variables sequenced as: concrete cover thickness > surface chloride concentration > chloride diffusion coefficient > critical chloride concentration; the time dependence of the diffusion coefficient has a significant effect on the time to corrosion initiation and cannot be ignored in the predictive model for both the high-performance or ordinary concrete; the number of freeze–thaw cycles and the tensile stress level are relatively insensitive but substantially detrimental to the reliability of corrosion initiation.

Performance evaluation of a commercial protective coating through field-exposure tests on three stone substrates

In the last decades, there have been several studies on Cultural Heritage regarding the performance of protective and consolidating coatings for the prevention of decay. A coating must have several characteristics such as efficiency, breathability, and must be durable and reversible. In this research work, the performance of a commercial protective product (Fosbuild FBLE 200) was evaluated. This coating is composed of a TiO2 nanopowder dispersed in an aqueous solution of an acrylic polymer. The product, which exhibits depolluting, antimicrobial, water-repellent and self-cleaning properties, has been applied on three different lithotypes: Carrara marble, Noto stone, and Comiso stone. Field-exposure tests were carried out in two different outdoor environments (Catania and Palermo) in order to assess its suitability. Promising results were obtained for the Carrara marble after one year of exposure; however, a decrease in effectiveness was observed at the end of the second year.

Selected Mechanical and Physical Properties of Thermally Modified Wood after Field Exposure Tests

This study aimed to evaluate the impact of thermal modification on the physical and mechanical properties of three different wood species from Bosnia and Herzegovina, namely beech wood (Fagus sylvatica L.), linden wood (Tilia cordata), and silver fir wood (Abies alba). The samples underwent thermal modification at five different temperatures (170 °C, 180 °C, 195 °C, 210 °C, and 220 °C) for varying durations (ranging from 78 to 276 min). After treatment, they were exposed to outdoor conditions for twelve months. The study examined the four-point bending strength, tensile force, color change, and surface quality of the modified and unmodified samples. The results showed that outdoor exposure negatively impacted the mechanical properties of the unmodified samples, especially in the linden wood which was 41% and the beech wood which was 42%. Additionally, outdoor exposure caused significant surface cracks in the thermally modified linden and beech wood. The study also found prominent color changes in the modified and unmodified samples during twelve months of exposure. The roughness of the samples was determined with a confocal laser scanning microscope, which showed that the roughness increased on both the axial and the longitudinal surfaces after weathering. The highest roughness for the fir wood was determined to be 15.6 µm. Overall, this study demonstrates the importance of wood modification and its impact on the use-value of wood products.

Model validation and 2-D hygrothermal simulations of wetting and drying behavior of cross-laminated timber

Cross-laminated timber (CLT) is one of the most important mass timber materials that are commonly used in mid-rise or even high-rise timber buildings. However, exposure to moisture during construction may increase the moisture damage risks, and impact the durability performance of CLT buildings. To investigate potential solutions for avoiding wetting of CLT components during construction, CLT specimens having different moisture protection measures were tested in the damp and mild wintertime climate in Vancouver. This follow-up work focuses on two-dimensional (2-D) hygrothermal modeling of the wetting and drying behavior of bare CLT (without any protection) and the validation with measurements from the field exposure test, emphasizing the influence of material properties. The hygrothermal models are firstly calibrated for two CLT specimens positioned horizontally, with and without a butt joint, by using material properties from different laboratory tests, and assuming different rain penetration paths. The calibrated models are then applied to simulate CLT specimens positioned vertically, which have end grain directly exposed to rain or damp concrete in the test. The work reveals that the moisture storage function above RH 95%, which includes the saturation water content reported in different literature, has a significant influence on the hygrothermal simulation results; meanwhile, assigning different water absorption coefficients for the transverse and longitudinal directions of wood significantly improves the accuracy of the hygrothermal model created for simulating rainwater penetration into the CLT panel. This paper provides a recommendation on how to properly model the CLT panels exposed to rainwater, which often occurs during construction.

Long-term state-driven atmospheric corrosion prediction of carbon steel in different corrosivity categories considering environmental effects

Abstract This study investigates an environment-centered, state-driven corrosion prognosis framework to predict the long-term atmospheric corrosion loss of metal materials, and this paper takes carbon steel as an example to show the establishment process of the framework. Unlike traditional power-linear prediction models that seldomly consider environmental impacts, the proposed model quantitatively establishes the correlations between corrosion loss and dynamic atmospheric environmental factors. A comprehensive power-linear function model integrating multiple atmospheric environmental factors is constructed, following the corrosion kinetics robustness. Under the proposed framework, the steady-state start time is evaluated, followed by the long-term corrosion loss prediction under different corrosivity categories and test sites. The applicability is justified via a case study of long-term field exposure tests of metal materials in China, as well as the experimental results of the ISO CORRAG program. By comparing with the traditional power model and ISO model, the experimental results demonstrate the capability and effectiveness of the proposed prognosis methodology in acquiring accurate corrosion state information and corrosion loss prediction results with less input corrosion information.

Correlation between Laboratory-Accelerated Corrosion and Field Exposure Test for High-Strength Stainless Steels.

Equipment in a long-term marine atmosphere environment is prone to corrosion failure. Natural field exposure tests usually require a long time to obtain corrosion information. This study worked out a laboratory-accelerated corrosion test method that has a strong correlation with the natural environment test in Wanning, Hainan, and can be used as the basis for life assessment and the prediction of two high-strength stainless-steel materials. The mathematical model of corrosion weight loss of two high-strength stainless steels (3Cr13 and 00Cr12Ni10MoTi) was established by a field exposure test and a laboratory-accelerated corrosion test. Then, the correlation between the field exposure test and the laboratory-accelerated corrosion test was evaluated using qualitative and quantitative methods, and the acceleration ratio was calculated using the accelerated switching factor (ASF) method. The results show that: (1) The corrosion morphology of the two stainless steels after 15 days of laboratory-accelerated corrosion testing is similar to that obtained after two years of field exposure. (2) The value of gray correlation between the laboratory-accelerated corrosion test and the field exposure test is not less than 0.75. (3) The acceleration ratio of both stainless steels increases with the corrosion test time in the laboratory. The corrosion prediction models for the two stainless steels are T3Cr13 = 6.234 t1.634 and T00Cr12Ni10MoTi = 55.693 t1.322, respectively.

Research on Dynamic Marine Atmospheric Corrosion Behavior of AZ31 Magnesium Alloy

The dynamic marine atmospheric corrosion behavior of AZ31 magnesium alloy was investigated in situ exposed on the deck of marine scientific research vessel for 1 year. The marine scientific research vessel carried out five voyages from the coast of China to the western Pacific Ocean, while the navigation track and environmental data were collected and analyzed. The corrosion rate and characteristics were evaluated by using weight loss tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. The corrosion rate from weight loss values was 52.23 μm∙y−1 after exposure for 1 year, which was several times higher than that of the static field exposure test in marine atmospheric environment of other reported literature. The main corrosion products were Mg5(CO3)4(OH)2·4H2O, MgCO3·3H2O and Mg2(OH)3Cl·4H2O. The corrosion was initiated from pitting corrosion and evolved into general corrosion gradually. The serious corrosion maybe due to the harsh corrosive environment with alternating changes in temperature and relative humidity caused by multiple longitude and latitude changes, and particularly high deposition rate of chloride during voyage, which was nearly twenty times that on the coast of China. This study provides effective data for the application of magnesium alloy in shipboard aircraft and other equipment, and provides a reference for indoor simulation experiments.

A comparison study of crevice corrosion on typical stainless steels under biofouling and artificial configurations

In this work, the crevice corrosion behavior and biofouling coverage of 316L stainless steel (316L SS), 2205 duplex stainless steel (2205 DSS), and 2507 super duplex stainless steel (2507 SDSS) in natural seawater were investigated through long-term field exposure tests. The results revealed that both artificial crevice corrosion and biofouling-induced crevice corrosion occurred on the surface of three stainless steels. The corrosion rate was ranked as 316L SS » 2205 DSS＞2507 SDSS. The deepest area of the artificial corrosion pit was at the edge of the crevice, which was related to the IR drop and acidification of the localized solution. The highest biofouling coverage and the most severe biofouling-induced corrosion occurred on the surface of 316L SS. The attachment of large organisms to the metal surface formed a fouling barrier layer, further blocking the flow of material over the crevices, and the artificial crevice corrosion was accelerated. The initiation of barnacle-induced corrosion was due to the formation of a crevice between the barnacle and the substrate, resulting in the entry of seawater. The acidification of the solution caused by catalytic-occluded cells was responsible for the continuous development of barnacle-induced corrosion, which was similar to the propagation of the artificial crevice corrosion.

Microclimate and Weathering in Cultural Heritage: Design of a Monitoring Apparatus for Field Exposure Tests

An innovative experimental method for the long-term monitoring of outdoor microclimate and material decay at cultural heritage sites was developed to aid the formulation of new damage functions and models for climate-change risk assessment. To that end, an apparatus for field exposure tests was designed to monitor a variety of historical building materials in different environmental settings. The data series acquired, i.e., surface temperature and moisture, are compared with the corresponding meteorological datasets on a local and regional scale. The apparatus is designed for supporting also the monitoring of the physical and chemical changes caused by weathering. This novel method is expected to provide insights into the interaction between historical materials and the environment, which can be exploited for the protection and conservation of cultural heritage.

Experimental and theoretical investigation of chloride ingress into concrete exposed to real marine environment

Chloride-induced corrosion is a critical issue that influences the durability and mechanical performance of reinforced concrete (RC) structures exposed to marine tidal and splash environments. This paper presents an experimental and theoretical investigation on the chloride transport behavior in concrete exposed to an aggressive marine environment for up to 720 days. Field exposure tests were performed in marine tidal and splash zones, and free chloride concentration profiles for different types of concrete after several exposure times, i.e. 90, 180, 360 and 720 days, were obtained. The effects of the water-to-cement ratio, binder type, exposure environment and exposure time on the time dependency of the chloride diffusion coefficient (D) and surface chloride concentration (Cs) were analyzed and discussed. Based on the obtained results, a modified time-dependent prediction model of chloride ingress into concrete was established and validated by considering the time-dependency effect of material and environmental factors. The results indicate that the comparisons of the predicted chloride profiles using the developed time-dependent prediction model were in good agreement with the results of the real marine exposure test.

Birnbaum-Saunders Durability Life Prediction Model of Site-Exposed Concrete in the Saline Soil Area

Aiming at the prominent problem of short durability life of concrete in saline soil area and the shortcomings of indoor accelerated test, an outdoor field exposure test was designed. The concrete specimens were semiburied in the Tianshui area with salinized soil characteristics, and nondestructive testing was conducted every 180d (days). The durability evaluation parameters and mechanical performance indexes were selected for macroscopic analysis, and the corrosion mechanism was analyzed by using the SEM image and the XRD phase. The Birnbaum-Saunders model based on physical failure and probability statistics was used for life prediction. The results show that there are rod-shaped and chip-shaped crystals growing from the surface of the gel and the internal holes in the exposed end and the embedded end of the concrete. However, the damage and deterioration of the buried end are more serious than those of the exposed end. The corrosion products mainly included ettringite, gypsum, calcium carbonate, sodium sulfate hydrate, carbosilite, and Friedel’s salt. The reliability life curve based on the Birnbaum-Saunders model can describe the whole process of exposed concrete from damage accumulation to failure. In addition, the dynamic modulus degradation index is more sensitive to concrete durability damage, and the life obtained by the Birnbaum-Saunders model is shorter than the quality degradation index. The life obtained by this degradation index is taken as the life of the concrete exposed in the saline soil site, and the concrete life of C30, C40, and C50 is about 3340d, 3930d, and 4360d, respectively.

Comparative investigation on copper atmospheric corrosion by electrochemical impedance and electrical resistance sensors

Electrochemical impedance (EIS) and thin electrical resistance (ER) sensors were invented for atmospheric corrosion measurement of copper (Cu) during cyclic wetting–drying/high–low temperature tests and field exposure tests. Three-month field exposure results showed that average corrosion rate of Cu measured by ER sensor was well in accordance with that by weight loss method. During cyclic wetting–drying test, EIS was proven to reflect sensitively time of wetting and drying on the surface of sensor. Although corrosion rate obtained from EIS had a similar tendency to that obtained from ER sensors, the former was more dependent on environmental humidity than the latter. When relative humidity was low than 60%, corrosion rate of Cu measured by EIS was much lower than that by weight loss method, mainly attributing to the fact that impedance sensor failed to detect corrosion current of interlaced Cu electrodes due to the breakdown of conductive passage composed of absorbed thin liquid film under low humidity condition. Promisingly, ER sensor was proven to be more suitable for atmospheric corrosion monitoring than electrochemical techniques because it could sensitively monitor thickness loss of Cu foil according to the Ohmic law, no matter how dry or wet the sensor surface is.

Evaluation of Chloride-Ion Diffusion Characteristics of Wave Power Marine Concrete Structures.

Wave power marine concrete structures generate electrical energy using waves. They are exposed to a multi-deterioration environment because of air and hydrostatic pressure and chloride attack. In this study, the effect of air pressure repeatedly generated by water level change of wave power marine concrete structures on the chloride-ion diffusion of marine concrete was analyzed. The chloride-ion diffusion of wave power marine concrete structures was evaluated. The results show that the air chamber and bypass room, which were subjected to repetitive air pressures caused by water level changes, showed a higher water-soluble chloride-ion content compared to the generator room and docking facility, which were subjected to atmospheric pressure. Field exposure tests and indoor chloride attack tests were performed using fabricated specimens to analyze the effect of pressure on chloride-ion penetration. It was confirmed that Portland blast furnace slag had a greater inhibitory effect on chloride-ion penetration than ordinary Portland cement. The concrete specimens subjected to pressure showed increased capillary pores and micro-cracks. We devised an equation for calculating the diffusion coefficient based on measured data and estimating the diffusion coefficient for the location receiving repeated air pressure by using the diffusion coefficient of the location receiving general atmospheric pressure.