Corrosion Factor Research Articles

Effect of simulated pitting corrosion on the tensile properties of steel

The buildings including steel-structured bridges, plants and ocean platforms which take steel as the main material are prone to fall into pitting corrosion. Mechanical properties are greatly affected by pitting corrosion and hence the security of buildings can hardly be guaranteed. The mechanical drilling and milling method is employed to form conical blind holes and then to simulate corrosion pits in present work, after which the effects of the shape, depth and distribution of corrosion pits on the tensile properties of steel have been systematically investigated. The results indicate that the fracture location of steels with corrosion pits occurred at the cross section with larger pitting corrosion factor. The load-displacement curves of the steels were changed due to the existence of corrosion pits, the yield platform got shorter and even disappeared, accompanied with poorer ductility and brittle fracture. Pit shape, depth and distribution impacted little on the ultimate load of tensile samples, the ultimate strength almost correlated only with the maximum cross-sectional area. However, the yield load of steels was affected by both pit shape and distribution. The elongation was mainly affected by pit denseness and depth, denser and deeper pits per unit area would give rise to smaller elongation. Finally, multivariate regression analysis was performed to acquire the prediction model of elongation.

Approach for fatigue damage assessment of welded structure considering coupling effect between stress and corrosion

This paper presents a new approach to assess time-dependent corrosion fatigue damage of welded joint considering the coupling effect between mechanical factor and corrosion factor. The high stress region around weld will accelerate corrosion and be more likely to induce nonuniform corrosion of welded joint. And the effect of loading on corrosion behavior of the steel in NaCl solution was investigated. The synergistic effect between applied elastic stress and chemical attack on Q235 steel was evaluated by electrochemical experiments. A side longitudinal of ship structure is selected as a case study. Time-dependent stress concentration factor of welded joint as a function of corrosion deterioration was analyzed, and the iterative process of stress and corrosion degeneration of plate thickness was used to simulate coupling effect basing on the results of experiment. The hot spot stress approach was adopted to calculate the fatigue damage. It is revealed that the nonuniform corrosion could influence fatigue damage of welded joint, and that impact will be more and more significant with the growth of corrosion year.

The Prediction of Grounding Grid Corrosion Rate Based on Vector Similarity and Fuzzy Closeness

Aiming at the grounding grid corrosion prediction involves many factors, the relationship is complex, and there are uncertainty and ambiguity in gaining involved factors, an efiective grounding grid corrosion rate prediction model is proposed. Consider sample set of every corrosion factories as feature vectors and then standardized them; by calculating the similarity of feature vectors and corrosion rate vectors, the weight of each corrosion factor on corrosion rate was obtained; treat membership function based on relevant relationship and half-Gaussian distribution as the core to determine the membership; use difierent sample properties have difierent corrosion rate contributions to do classiflcation, and combine closeness principles to predict corrosion rate. The application results show that the model can efiectively predict the grounding grid corrosion rate of those ground web sites who have near distance or similar soil physical and chemical indicators.

Methods for the Evaluation of Fracture and Strength of Pipeline Steels and Structures Under the Action of Working Media. Part І. Influence of the Corrosion Factor

We generalize contemporary methods used for the evaluation of strength and fracture hazard of elements of pipeline structures with the use of approaches of fracture mechanics of materials, by taking into account specific features of influence of corrosive factors. The stages of initial corrosion damage to the metal and of the surface corrosion-fatigue cracking in pipeline steels are analyzed. We discover the influence of the chemical composition of the medium, frequency and stress ratio of the loading cycle, and the time of operation on their cyclic corrosion crack resistance. For the expert evaluation of the serviceability and fracture hazard of pipeline systems with corrosion cracklike defects, we propose to use special diagrams containing three characteristics zones: zone of safe operation, zone of operation with predicted development of the existing cracklike defects, and zone of brittle fracture hazard.

Coupled Effect of Loading and Environment of Concrete Bridge in Service Life

A numerical method is proposed to study load and the environment couple effect during the service of a concrete bridge. By studying the corrosion process of reinforcement bars, the strain of the bars is decomposed into two parts, elastic strain and corrosion strain, and their ratio is defined as the corrosion factor. The time-dependent constitution of corrosion of the steel bar is obtained by introducing a nominal elastic module. According to the virtual work principle, the finite element formulation of the reinforcement concrete element is derived, and the computation sequence determined using the time history method is illustrated. The nonlinear finite element program is realized by the Fortran program to numerically solve the problem, which is verified by testing a model of three reinforced concrete beams. The results show that both stiffness matrix and the additional nodal load of the reinforcement concrete element should be considered in the couple effect analysis. The proposed method can be used to predict long-term mechanical properties of concrete bridges.

Deformation Behavior of Corroded Steel Bar Based on Viscoelastic Theory

This paper shows the corrosion of steel bar from a new perspective with viscoelasticity theory. The strain of steel bar is decomposed as initial elastic strain and creep strain, and the creep strain is caused by corrosion. In order to analysis creep strain, corrosion factor and corrosion strain function were introduced to reflect the deformation behavior. Then integral constitutive relation of corroded bar was deduced according to the above assumption. As a special case of this approach, the corrosion factor of steel bar in atmospheric environment is introduced. The results indicate that the corrosion factor increase with diameter deducing, and the deformation of the steel bar possess the acceleration creep behavior during the corrosion process.

Use of the Theory of Hardening Factor for Predicting the Properties of Articles from Heat-Hardenable Aluminum Alloy V91

The effect of modes of quenching cooling on the structure and corrosion resistance of heat-hardenable aluminum alloy V91T3 of the Al – Zn – Mg – Cu system is studied. Experimental data are used to plot the “temperature – hardness” and “temperature – time – corrosion rate” diagrams, which make it possible to predict the corrosion resistance of alloy V91T3 for various modes of quenching cooling. Equations relating the mass corrosion factor and the rate of pitting corrosion to the values of the hardening factor are suggested. The data obtained are used for predicting the phase composition and properties of component parts of a fabricated press mold.

Effects of rainfall characteristics on corrosion indices in Korean river basins

Corrosion indices have been widely used to assess water quality in countries such as the USA, Japan, France, and The Netherlands since Langelier first introduced this concept in 1936. The most commonly used corrosion indices are the Langelier saturation index (LSI), the Ryznar stability index (RSI), and the aggressiveness index (AI). Here, the changes in LSI, RSI, and AI due to corrosion factors such as pH, Ca hardness, and alkalinity were characterized according to the rainfall during the rainy season at four river basins in Korea. The results of a sensitivity analysis of corrosion indices with varying corrosion factors showed that pH had the greatest effect with a value of 0.1, which indicates that pH affects corrosion more than any other corrosion factor. By comparing the monthly pattern of corrosion factors at each river, it was found that pH and alkalinity decreased during the rainy season, whereas Ca hardness showed only subtle changes across the year. In addition, when comparing the relationship between the corrosion factors and corrosion indices at each river basin in the rainy season, LSI, RSI, and AI all showed strong corrosiveness with values of −2.97, 12.80, and 9.26, respectively, in the Nakdong River basin.

Application of wire beam electrode technique to investigate initiation and propagation of rebar corrosion

Multi-electrode technique named as wire beam electrode (WBE) was used to study pitting corrosion of rebar under concrete cover. When WBE embedded mortar sample was immersed in NaCl solution, uneven distributions of galvanic current and open circuit potential (OCP) on the WBE were observed due to the initiation of pitting corrosion. The following oxygen depletion in mortar facilitated the negative shift of the OCP and the smoothing of the current and potential distributions. Wetting–drying cycle experiments showed that corrosion products instead of oxygen in wet mortar specimen sustained the propagation of pitting corrosion due to Fe (III) taking part in cathodic depolarization during oxygen-deficient wet period, which was confirmed by micro-Raman spectroscopy. In addition, new pitting corrosion occurred mainly near the corrosion products, leading to preferentially horizontal propagation of rust layer on the WBE. A localized corrosion factor was further presented to quantify the localised corrosion based on galvanic current maps.

Dynamic fatigue of two-dimensional carbon/carbon composites

The dynamic fatigue of a chemical vapor infiltration 2D-C/C composite was investigated in three-point flexure using different stress rates from 0.07 to 70MPas−1. Flexure strength of the specimens increased in proportion to the increase of stress rate. From the ln σ–ln σ̇ diagram, stress corrosion factor n was obtained. The n value of 58 in the present work indicated that slow crack growth controlled the fracture process. The fracture under different stress rates shows characteristics of the slow crack growth, which agree with the result of dynamic fatigue.

The Corrosion of Concrete Shaft Lining of Mine and its Related Research Progress

With the extensive use of concrete materials, concrete corrosion as an important hazardous factor of engineering safety and its impact on the engineering safety is receiving attention gradually. In order to study its impact on the safety of mining engineering, this paper summarized the corrosion factor of concrete shaft lining of mine and its research progress, and combined with the actual progress of the concrete corrosion. The author came to the conclusion that we should pay attention to the study of the corrosion of concrete shaft lining of mine, at the same time, analyzed the feasibility of the study. The authors believe that, at the present stage, studies of concrete corrosion are more comprehensive and thorough, and coupled with the comprehensive understanding of the underground environment. It is perfectly placed to study the problems of the corrosion of concrete shaft lining of mine deep and systematically.

Major corrosion factors in the CO 2 and H 2 S coexistent environment and the relative anti-corrosion method: Taking Tazhong I gas field, Tarim Basin, as an example

Abstract Anti-corrosion techniques are studied to deal with the CO 2 and H 2 S coexistent environment of the Tazhong I gas field. Orthogonal experiment with five different factors and levels is carried out to compare the influence of the factors on the corrosion rate of the sulfur-resistant tubing. These five factors are pressure of CO 2 , pressure of H 2 S, temperature, content of Cl − , and water cut. It is found that CO 2 pressure is the major corrosion factor. The combination of sulfur resistance tubing and corrosion inhibitor is selected as the anti-corrosion method and the proper corrosion inhibitor named YU-4 is designed according to the result of orthogonal experiment. This anti-corrosion method was used in 12 wells of the Tazhong I gas field, achieving good results. The average corrosion rate of Well TZ83 decreased from 1.23 mm/a to 0.025 mm/a and the corrosion rate of Well TZ623 decreased from 0.370 mm/a to 0.016 mm/a.

Effect of Corrosive Factors on Progression of Pitting Corrosion of Welded SUS304 Steel under Freezing and Thawing Corrosive Environment

It has been reported that pitting corrosion occurs in stainless steel under the specific conditions which a corrosion factor superimposes. In cold and snowy area, welded structures on the outdoors are exposed to combinational environment of the salt damage and the freezing damage, in which the corrosive solution containing Cl- chlorine ions from the sea breeze and snow melting agents undergo freezing-thawing cycles during the winter. The cause of pitting corrosion phenomenon which occurs in the welded stainless steel under such a combinational environment has not yet been clarified. In the previous report, accelerated pitting corrosion is confirmed to have occurred as a result of concentration cell corrosion due to a local concentration of Cl- chlorine ion around a weld bead during freezing and thawing of the solution. In the present study, it is investigated that the effect of corrosive factors on the progression of pitting corrosion in welded austenitic stainless steel under freezing and thawing corrosive environment. Austenitic stainless steel SUS 304 plates with bead-on-plate welding are used as specimens. The specimens are fully immersed in FeCl3 solution. The freezing-thawing environment is created by temperature cycling form 20°C to -20°C. One cycle of freezing-thawing is 12 hours and 24 hours. As a result, in the austenitic stainless steels under a freezing and thawing corrosive environment, it became evident that sensitive metallographic structures influences an occurrence of large scale pitting corrosion, and a stress level influences an accelerated progression of the pitting corrosion.

Durability of asphalt mixture in different corrosion solution

The corrosion to asphalt mixture under different kinds of corrosion solution, such as pH=2 solution, pH=12 solution, pH = 12 solution and 10% Na2SO4 solution, was studied. The performance attenuation of asphalt mixture was analyzed under the normal environment and the freeze-thaw environment, and the analysis was given on the sensitivity of the test results to the evaluation index. The experimental results show that the performance of asphalt mixture is attenuated faster under the acidic solution, alkaline solution and sulfate solution. Corrosion factor Kc, freeze-thaw corrosion factor Kf, and freeze-thaw effect factor Kfc are proposed to evaluate asphalt mixture resistance to corrosion in different kinds of corrosion solution. The values of Kc and Kfc decrease with the increasing of corrosion time. The change rule of Kf show that the rate of corrosion is decreased by the action of freeze-thaw in acidic solution and in alkaline solution, but is increased by the action of freeze-thaw in sulfate solution. The microscopic analysis indicates that acid solution reacts with aggregate of asphalt mixture, alkaline solution reacts with asphalt cement of asphalt mixture, the surface tension of sulfate solution and crystallization of sulfate are the main reasons which weak the performance of asphalt mixture.

Effect of corrosion on performance of fin-and-tube heat exchangers with different fin materials

Corrosion on heat exchangers, which have been used long-term, could deteriorate the performance of air conditioning system. In the present study, standard salt spray tests (48 and 96 h) were carried out on evaporators with aluminum (Al) fins and copper (Cu) fins to accelerate corrosion. The micrographs of the Al fins and Cu fins before and after corrosion were obtained. The performances of the samples before and after the corrosion were tested in a psychrometric calorimeter test facility. After the 96 h salt spray test, the cooling capacity decay rate of the sample with Al fins was 12%, whereas that of the sample with Cu fins was only 2%. The average overall heat transfer coefficients of the sample with Cu fins were 55.8%, 67.4% and 69.4% larger than those of the sample with Al fins before corrosion and after the 48 and 96 h salt spray test, respectively. The corrosion factor in the thermal resistance of the evaporator after the salt spray was also investigated. After the 96 h salt spray corrosion test, the proportion of corrosion factor was 27% of the overall thermal resistance of the evaporator with Al fins. For the evaporator with Cu fins, the proportion was 19.1% at its maximum. The effects of corrosion to the air side pressure drop of the different samples were also studied. The change of the air side pressure drop was within 5 Pa for each sample after the salt spray test.

Experimental Determination of Aircraft Structural Material Life Envelope

A new approach to reflect the relation of aircraft structural calendar life and fatigue life is established by pre-corrosion and fatigue test with 2A12 alloy specimens. The corrosion factor curve is fitted from the test, and then aircraft structural corrosion and fatigue interactive process during actual in-service environment is simulated. Furthermore, combining with Miner linear cumulative damage theory and the method of ‘calendar life tending to minimum’, life envelope is found. The result shows that flight strength is the key factor for aircraft structural life, and the envelope can be used to realize single aircraft structural life surveillance.

Corrosion Factor and Prevention of the Steel Plate in the Landfill Sites Using the Steel Plate Liner

Corrosion Factor and Prevention of the Steel Plate in the Landfill Sites Using the Steel Plate Liner

Corrosion Estimation of Stainless Steel in Nitric Acid by an Optoelectronic Instrument Based on Diffuse Light Scattering Pattern Measurement

This paper presents the design and implementation of an optoelectronic instrument for measuring corrosion of metal surfaces, based on measurement of lightwave scattering pattern. The instrument consists of a thin beam light emitting diode (LED) that illuminates a tiny spot on the metal surface, and an array of photodiodes spread over a hemispherical structure covering the surface to record the light scattering pattern. A mathematical model of light scattering by a corroded metal surface is constructed in which a newly defined corrosion factor is correlated to light scattering pattern. The corrosion factor derived from the scattering pattern gives a measure of the degree of corrosion in a scale from 0 to 100. The temporal behavior of corrosion of stainless steel samples immersed in nitric acid of various concentrations is presented graphically. A semi empirical mathematical model describing the corrosion and dissolution processes in terms of the well-known bilogarithmic laws fits very well with the experimental results. The measured corrosion factor and the corresponding roughness factor as measured by an atomic force microscope are compared to show the relation between the two.

SUS304ステンレス鋼のすきま内外における腐食に及ぼす塩種と乾湿条件の影響

As the requirement for durability of automobile increase, the application of type 304 stainless steel is expanding because of its high workability and corrosion resistance. On the other hand, one of the main corrosion environments of automobile is chloride condition caused by deicing salt or sea salt particle, and it becomes more severe when added to the wet/dry cyclic condition that is specific to automobile. In this case, the corrosion resistance is not enough even if the stainless steel is applied. In the case of stainless steel, crevice corrosion is mainly concerned in chloride environment. Pitting corrosion, however, can sometimes occur at non-crevice site. The purpose of this study is to clarify how the corrosion factor such as salt composition or wet/dry condition affects to the corrosion behavior of type 304 stainless steel inside and outside of crevice. The corrosion factors described above were evaluated by the corrosion test method developed in our previous work. Furthermore, electrochemical measurements were conducted. As a result, when NaCl is used for chloride addition, there is more severe corrosion at crevice than non-crevice site regardless of wet/dry condition. However, when sea salt particle or CaCl2 that is a major component of deicing salt are used, corrosion sites differ depending on wet/dry condition. That is, corrosion is severe at crevice site under high humidity condition of more than 60%RH, while pitting corrosion is prominent at non-crevice site under low humidity of less than 40%RH. Considering the corrosion behavior under various wet/dry conditions, main corrosion factor of sea salt particle is not NaCl but MgCl2 that is not major component.

Atmospheric corrosion mapping of copper surfaces from diffuse light scattering measurements by an optoelectronic sensor system

A novel light scattering technique for mapping metal surface corrosion is presented and its results on copper exposed to atmosphere are reported. The front end of the instrument is made up of a sensor module comprising a thin beam light emitting diode (LED) illuminating a small spot on the metal surface, and a matched pair of photodetectors, one for capturing the reflected light and the other for sampling the scattered light. The analog photocurrent signals are digitized and processed online by a personal computer (PC) to determine the corrosion factor defined in terms of the two current values. By scanning the sample surface using the light beam and by computing the corrosion factor values simultaneously, a three dimensional graph and a two dimensional contour map are generated in the PC using Matlab tools. The values of the corrosion factor measured in different durations of exposure to atmosphere, which obey a bilogarithmic law, testify to the validity of our mathematical model.