Annual Corrosion Rate Research Articles

Characteristics and effects of electromagnetic interference from UHVDC and geomagnetic storms on buried pipelines

The influence of ±800 kV ultra-high voltage direct current (UHVDC) transmission monopole operation on buried oil pipelines was compared between the 6250 A grounding pole current conditions of the Zalute-Qingzhou Project on December 24, 2017 and the Shanghai Temple-Shandong Project on January 2, 2017. Besides, the influence of geomagnetic storms on the safety of buried oil pipelines were also analyzed based on monitoring data from the geoelectric field of the China Anqiu geomagnetic station on September 9 and 29, 2017. The results show that the influence of the DC grounding pole current on the pipeline is related to the distance between the ground electrode and the pipeline, the operating state of the potentiostat, and the spacing of the insulating flange on the pipeline. The geomagnetically induced current and pipe-soil potential offsets for the geomagnetic storm intruding the pipeline are related to the rate of change for the geomagnetic field. There are differences in the stray current and PSP generation mechanisms for the intruded pipeline caused by the two interference sources: the intensity and influence range of the interference source, and the annual average corrosion rate of the pipeline. Compared with the DC grounding pole current, the geomagnetic storm has a greater interference effect on buried pipelines.

System Analysis of the Stress State of a Structure during Interaction with an Aggressive Environment

It is shown that the implementation of effective anticorrosive protection of a steel structure and the choice of its optimal parameters depend on the quantitative characteristics of the corrosion rate. This value substantially depends on the soil moisture, with the maximum value being observed in spring after snowmelt. During this period, corrosion processes are sharply activated, which can significantly change the average annual corrosion rate, which at other times may remain small. The higher the voltage in the metal and the more often and with greater amplitude it changes, the higher the corruption rate. The point failure of a steel structure can be distinguished from hydrogen embrittlement by means of a fractographic study of cracked surfaces. Cracks formed as a result of hydrogen embrittlement have no signs of corrosion, unlike cracks formed as a result of stress in a metal and corrosion.

Application of numerical calculation to simulation analysis of stray current corrosion in radiator of HVDC Converter Valve

According to the electrical structure design of the converter valve, the stray current scattered in the water path of the converter valve tower is coupled in the internal waterway of the aluminum radiator. It promotes the occurrence of corrosion on the inner surface of the waterway. However, due to the wide range of stray current in the valve tower distribution pipe, many factors affecting the properties of fluid and the actual engineering not allowed to be measured, and so on. For a long time, the corrosion of converter valve radiator has always been an urgent technical problem to be solved in the field of DC transmission. It has received extensive attention in various research institutions around the world. In this paper, according to the distribution pipe of 500kV light-triggered converter valve tower, the structure model and equivalent circuit model of the water path are built and the mechanism of stray current corrosion of aluminum radiator is analyzed. At the same time, the circuit simulation software is used, and according to Faraday’s law, the stray current, corrosion rate and annual corrosion rate of aluminum radiator in distribution pipe were calculated quantitatively. According to the numerical calculation results, the corrosion of aluminum radiator is compared with that of actual engineering aluminum radiator, the primary and secondary relationship of stray current corrosion in aluminum radiator corrosion is put forward, which provides the basis and reference for system optimization and engineering transformation.

Corrosion and inhibition process of carbon steel in LiBr-H2O solution

Lithium bromide (LiBr)-H2O triple-effect absorption chillers are supposed to have a much higher carbon steel corrosion rate under high temperature than double-effect ones. Although the annual corrosion rate was investigated in our previous study, a simple extrapolation with experimental data for a short period of time can cause very significant errors because the corrosion process becomes quite complicated if a corrosion inhibitor exists in the solution. Therefore, in this study, corrosion and inhibition characteristics over time have been investigated for carbon steel specimens in LiBr-H2O solution under the optimal operation conditions of double- and triple-effect absorption chillers. Pyrex tube ampoules containing a carbon steel specimen and the 63 % LiBr-H2O solution with a corrosion inhibitor (lithium molybdate, Li2MoO4) were prepared and placed in a high-temperature oven at 150 °C and 200 °C, which are typical operation temperatures of double- and triple-effect absorption chillers, respectively. After various exposure times (25–4000 hours), the ampoules were opened and analyzed using three methods: Analysis of mass loss, solution analysis, and microscopic image analysis. Results indicated that the passive films were formed not linearly with time but rapidly at the beginning. Moreover, the concentration of the corrosion inhibitor (Li2MoO4) should be maintained above 100 ppm for stable passive films. To explain the experimental data, a model with three stages of corrosion and inhibition process was proposed. The present study is expected to give important information for the development of triple-effect absorption chillers.

Sensitivity of dose-response function for carbon steel under various conditions in Slovakia

Abstract Degradation of materials, especially reinforcement in the reinforced concrete members, is very important phenomenon not only in the traffic infrastructure network. Here can raise the question, how high is the corrosivity of atmosphere in various areas in Slovakia and how the variability of climatic parameters affects the corrosion rate rcorr. The first annual corrosion rate of carbon steel is possible to calculate according to dose-response function described in the actual standard EN ISO 9223. The dose-response function is relatively complicated formula, which contains mathematical expressions like exponential-function or power-function. So, it is difficult to assume which one of the four input parameters, like temperature T, relative humidity Rh, content of chloride ions Cl- or sulphur dioxide SO2 has higher sensitivity on the corrosion rate calculated from the function. The paper is focused on the sensitivity analysis of dose-response function in the range of input parameters monitored by Slovak hydrometeorogical institute and the effect of spraying or splashing transport mechanisms of de-icing salt was observed, as well.

A novel chemical heat pump cycle for cooling and heating

The absorption heat pump cycle based on LiBr/H2O has shortcomings of easy crystallization, severe corrosion, and the limitation in the temperature rise. In this study, a novel chemical heat pump cycle is proposed to overcome these issues. The thermal performance of the chemical heat pump using NaNO3/H2O is simply calculated for communication. The results show that the chemical heat pump can work at a lower generating temperature of 73.9 °C and avoid the crystallization issue when simultaneously supplying heating and cooling at 60 °C and 7 °C, respectively. Moreover, the annual corrosion rate of carbon steel in the NaNO3/H2O strong solution is only 7.09 μm y−1 at 180 °C. The chemical heat pump has the advantages of lower generating temperature and corrosiveness, as well as larger temperature operating range and temperature rise in comparison to the absorption cycle using LiBr/H2O and other alternative working pairs. However, the chemical heat pump has a lower thermal performance, and the COPc, COPh, and COPo are 0.11, 1.11, and 1.22, respectively. In the future studies, it is expected that the chemical heat pump will achieve a much higher COP, after taking into account of a multiple-effect cycle, as well as a chemical refrigerant with a larger dissolution enthalpy and solubility slope.

Erosion-corrosion behavior and electrochemical performance of Hastelloy C22 coatings under impingement

The erosion-corrosion behavior of Hastelloy C22 coating prepared by multilayer laser cladding technology is investigated under impingement by solid-liquid flow. Three external factors are taken into consideration including fluid flow velocity, impact angle and erosion time. The total weight loss and corrosion current density increase with the increase in flow velocity. But the passive current density reduces when velocity is over 4 m/s. The combination effect of shear and normal stress leads to the maximum of total weight loss at 60°, but electrochemical measurements show lowest corrosion resistance at 30° due to dominant shear stress and highest value at 60° because of stronger protection of passive film. As expected, both weight loss and corrosion rate increase with erosion time extending. The microhardness of coating surface increases after impingement. The impact of solid particles on surface produces typical craters with different shapes and sizes. The low annual corrosion rate of Hastelloy C22 coating shows the efficacity of multilayer laser cladding technology.

Modeling Corrosion in Suspension Bridge Main Cables. I: Annual Corrosion Rate

Modeling Corrosion in Suspension Bridge Main Cables. I: Annual Corrosion Rate

Modeling Corrosion in Suspension Bridge Main Cables. II: Long-Term Corrosion and Remaining Strength

Reliably assessing the condition and safety of suspension bridges poses the problem of determining the remaining strength of bridge cables in their present state. Corrosion of the steel wires, which together comprise the main cable, is universally recognized as the main cause of the reduction in strength. Hidden by the protective cable wrapping, this corrosion often goes undetected and unmonitored for years, discovered only during costly and intrusive inspections. This paper presents a method for estimating the remaining capacity of cables that is based on monitored environmental condition data. The long-term corrosion rate of bridge wires, C(t), can be described by the exponential expression C(t)=Atn where A is the annual corrosion rate for a metal free of corrosion products, t is the time in years, and n is an exponent dependent on the type of metal as well as the prevalent environmental conditions. In this study, a novel approach that relies on tensile test data gathered during a bridge inspection, coupled with environmental condition data typical to the locality of the bridge was used to quantify n. Temperature and relative humidity distributions across the cable section required to estimate the corrosion rate were correlated to externally monitored inputs using data from a full-scale mock-up cable subject to cyclic temperature and humidity conditions. Using the developed method, the evolution of cable strength over time under typical environmental conditions was simulated for a 100-year-old cable (Williamsburg Bridge in New York City) as well as a new, hypothetical bridge cable composed of galvanized wires. In the numerical simulation of the Williamsburg Bridge cable, the reduction in cable strength between the years 1988 and 2100 was estimated between 3.2 and 7.0%. Extending this concept, the methodology presented in this paper for estimating the remaining strength of suspension bridge cables may be readily adapted to other bridges and can be used to complement the current best practices for bridge inspection.

Microstructure and properties of TP2 copper tube with La microalloying by horizontal continuous casting

The TP2 copper tube was prepared with La microalloying by horizontal continuous casting (HCC). The absorptivity of La and its effects on microstructure, tensile and corrosion properties of HCC TP2 copper tube were studied by means of the inductively coupled plasma optical emission spectrometer (ICP-OES), optical microscope (OM), scanning electron microscope (SEM) and potentiodynamic polarization measurements. The results show that the absorptivity of La in the HCC TP2 copper tube is about 15% under antivacuum conditions due to the good chemical activities of La. The impurity elements in copper tube such as O, S, Pb and Si can be significantly reduced, and the average columnar dendrite spacing of the copper tube can also be reduced from 2.21 mm to 0.93 mm by adding La. The ultimate tensile strength and the elongation with and without La addition are almost unchanged. However, the annual corrosion rate of the HCC TP2 copper tube is reduced from 10.18 mm•a-1 to 9.37 mm•a-1 by the purification effect of trace La.

Hydrogen-Free Carburization on the Surface of Commercial Purity Titanium by Equipotential Hollow-Cathode Glow Discharge

The treatment of hydrogen-free carburization was applied on commercial purity titanium by the technology of equipotential hollow-cathode glow discharge at the commercial purity titanium phase transition temperature. The morphology, distribution of composition and phase composition were analyzed by the scanning electron microscope, the energy dispersive spectrometer, the X-ray diffraction, respectively; the tribology capability of the sample was studied by the friction and wear tester; the corrosion resistance of the samples in 3.5% NaCl solution was studied under the room temperature static condition by the electrochemical workstation. The results show that the high hardness alloy layer forms on the commercial purity titanium surface by the treatment of hydrogen-free carburization, and the maximum thickness of the carburized layer is 7.5 μm; and the maximum HV 0.2 hardness is 12.98 GPa, which is 5.43 times of that of the substrate. Due to the improved surface hardness, the wear resistance on the surface of the sample increases significantly, and the average friction coefficient is only 0.312, which obviously decreases compared with 0.746 of the original sample. The minimum annual corrosion rate of the samples is 1/11 of the original sample in 3.5% NaCl solution. So the wear resistance and corrosion resistance obviously improve in the premise of keeping the mechanical properties of the substrate.

Corrosion behavior of novel Cu–Ni–Al–Si alloy with super-high strength in 3.5% NaCl solution

A novel Cu–6.5Ni–1Al–1Si–0.15Mg–0.15Ce alloy with super-high strength was designed and its corrosion behavior in 3.5% NaCl solution at 25 °C was investigated by the means of SEM observation, TEM observation and XPS analysis. The alloy after solution treatment, 80% cold rolling and aging at 450 °C for 1 h had the best comprehensive properties with hardness of HV 314, electrical conductivity of 19.4% IACS, tensile strength of 1017 MPa, and average annual corrosion rate of 0.028 mm/a. The oxides and chloride products formed at first, followed by the formation of dyroxides products. The alloy showed super-high strength, good electrical conductivity and corrosion resistant because Ni2Si hindered the precipitation of large NiAl at the grain boundary and the denickelefication of the alloy.

Annual atmospheric corrosion rate and dose-response function for carbon steel in Bogotá

This paper presents an assessment on the behavior of plain carbon steel exposure to the atmosphere of Bogotá. The main climate and environmental parameters, including relative humidity (RH), temperature (T), sulphur dioxide deposition (DSO2) and particulate matter deposition (DPM) were measured. Furthermore, mass loss of AISI/SAE 1006 plain carbon steel coupons was measured along one year. In this case, coupons were exposed in eight test sites located across the city of Bogotá. Results show that the corrosion rate of carbon steel is less than 35μm yr−1 after one year. It was found that the west part of the city has the greatest aggressivity, which has the highest levels of DPM and DSO2, related with the characteristics of the anthropogenic activities distribution across the city. A dose-response function of plain carbon steel exposure to the atmosphere of Bogotá, based on RH, T and DSO2, was obtained.

Copper corrosion in hot and dry atmosphere environment in Turpan, China

The atmospheric corrosion behavior of pure copper exposed for three years in Turpan, China, which is a typical hot and dry atmosphere environment, was investigated using mass-loss tests, morphology observations, composition analyses, and electrochemical techniques. The results indicated that the annual corrosion rate of pure copper was approximately 2.90 μm/a. An uneven distribution of corrosion products was observed by scanning electron microscopy; this uneven distribution was attributed to the dehydration process during wet–dry and cold–hot cycles, and the compositions mainly consisted of cuprite (Cu2O) and atacamite (Cu2Cl(OH)3). Electrochemical measurements showed that deposits on copper improved its resistance to corrosion and the protectiveness decreased with increasing temperature. On the other hand, results obtained using the scanning vibrating electrode technique showed that the porous and uneven structure of the deposit layer generated a spatial separation of cathodic and anodic reaction sites, which accelerated the corrosion process in wet and rainy weather.

Long-Term Corrosion of Copper in Hot and Dry Atmosphere in Turpan, China

Atmospheric exposure tests were conducted on pure copper exposed to the atmosphere for a four-year period in Turpan, China, a typical hot and dry environment. The experiments included weight-loss tests, morphology observations, composition analyses, and electrochemical techniques. The results indicated that the annual corrosion rate of pure copper was approximately 2.24 g/m2/year, and an uneven distribution of corrosion products was observed by scanning electron microscopy. This was attributed to the dehydration process that occurred during wet-dry and cold-hot cycles. The corrosion products mainly comprised cuprite (Cu2O) and atacamite (Cu2Cl(OH)3). Electrochemical measurements showed that deposits on copper improved its resistance to corrosion, but the protectiveness decreased with increasing temperature.

Statistical properties of bulk carrier longitudinal strength

The paper focuses on time-variant longitudinal strength of bulk carriers under corrosion wastage, applying both Taylor series expansion method and Monte Carlo simulation. Hull girder section modulus and ultimate bending moment capacity are determined, by classical beam theory and the commonly applied incremental-iterative approach, respectively. Two main aspects are fully discussed and investigated, according to the final recommendations of last ISSC Report. The former regards the covariance between annual corrosion rates of individual structural members, commonly assumed as uncorrelated. Really, as it is conceivable that a certain correlation exists, three different cases are investigated: uncorrelated variables, fully correlated variables, full correlation between structural members belonging to the same category of compartments. The latter investigates the probability density function of both hull girder section modulus and ultimate bending capacity, because the Central Limit Theorem cannot be applied when correlation among random variables exists. Finally, as a test example, the bulk carrier section, presented in the last ISSC benchmark study, is analysed.

Corrosion Behaviour of AISI 304 Stainless Steel with Solar Salt Heat Transfer Fluid

In an effort to understand the compatibility between the heat transfer medium and the structural materials used in concentrated solar power plants, the corrosion behavior of AISI 304 stainless steel (18 wt.% Cr, 8 wt.% Ni) in a molten solar salt mixture (53 wt. % KNO3, 40 wt. % NaNO2,7 wt. % NaNO3) has been investigated. The 304 stainless steel coupon samples were fully immersed and isothermally exposed to solar salt at 530°C for 250, 500, and 750 hours in air. X-ray diffraction and scanning electron microscopy with X-ray energy-dispersive spectroscopy were employed to examine the extent of corrosion and identify the corrosion products. Oxides of iron were found to be the primary corrosion products in the presence of the molten alkali nitrates-nitrite salt mixture because of the dissolution of the protective chromium oxide (Cr2O3) scale formed on 304 stainless steel coupons. The corrosion scale was uniform in thickness and chromium-iron oxide was found near the AISI 304. This indicates that the scale formed, particularly on the upper layer with presence of sodium-iron-oxide is protective, and forms an effective barrier against penetration of fused solar salt. By extrapolation, annual corrosion rate is estimated to reach 0.784 mils per year. Corrosion behavior of AISI 304 stainless steel is discussed in terms of thermodynamics and reaction paths.

Surface modification of pure titanium by plasma tantalumising

In order to improve corrosion resistance of pure titanium in strong acid solution, the tantalum modified layer was formed on the pure titanium surface by double glow plasma surface tantalumising. The modification layer was comprised of deposition layer and diffusion layer, which metallurgically adhered to the substrate. Tantalum element decreased with the case depth. The corrosion resistance of the tantalum modified layer in HCl solution was investigated by weight loss method and electrochemical measurements, and the corrosion morphology (SEM) was studied by SEM and X-ray diffraction. The annual corrosion rate of the modified layer was only 12 and 21% of pure titanium in 10 and 20 wt-% HCl solution respectively, and the corrosion rate was still small in 30% HCl solution. In concentrated acid for 120 h, it was found that there was significant pitting corrosion on the surface of pure titanium, while no pitting corrosion could be perceived in the modified layer. The main reason for the good corrosion resistance was a compact, stable tantalum oxidation film formed at the surface of the modified layer.

Effect of Aging Temperature on Corrosion Behaviors of Maraging Stainless Steel in Seawater

The seawater corrosion resistance of 00Cr13Ni7Co5Mo4W maraging stainless steel by different temperature aging treatment have been studied by using potentiodynamic polarization curves and uniform corrosion immersion test, the corrosion morphology and microstructure of maraging stainless steel were analyzed by scanning electron microscopy and metallographic microscope. The results showed that 00Cr13Ni7Co5Mo4W maraging stainless steel of different aging temperature processing had occurred the obvious self-passivation, the breakdown potential of maraging stainless steel after different temperature aging treatment are E 470°C >E 490°C >E 510°C >E 450°C, and the corrosion rate relationship are R 470°C 490°C 510°C450°C .The breakdown potential and the annual average corrosion rate of 00Cr13Ni7Co5Mo4W maraging stainless steel are 300 mV and 1.2590µm/a respectively, with the best resistance to seawater corrosion.

Study on Corrosion Resistance of 00Cr13Ni7Co5Mo4W Maraging Stainless Steel in Seawater

The seawater corrosion resistance performances of 00Cr13Ni7Co5Mo4W maraging stainless steel were contrastively investigated by using electrochemical measurements and chemical immersion tests. The results show that breakdown potential of specimen in aging-state is reduced due to R phase precipices during aging. The difference between breakdown potential and protection potential of maraging stainless steel is little, and the restorability of the passive film is strong with small-scale shallow pits. After solution treated at 1100°C for 1h followed by aged 490°C for 8h,the breakdown potential and the annual corrosion rate of 00Cr13Ni7Co5Mo4W maraging stainless steel were 230 mV and 1.5091µm/a , respectively, showing a good resistance to seawater corrosion.