Formation Of Corrosion Products Research Articles

Probabilistic quantitative analysis on the contents of sulfate corrosion products in concrete

A probabilistic quantitative method is proposed in this paper to depict the random evolution process of the contents of sulfate corrosion products (CSCP) in concrete. The method includes the stochastic kinetic equation established according to sulfate corrosion reactions leading to formation of corrosion products, and probability description of the CSCP. The stochastic kinetic equation is presented based on the chemical Langevin equation for complex reactions (CLE-CR), in which internal fluctuations are regarded as white Gaussian noises. Sulfate corrosion reactions are assumed to occur in a well-stirred system without considering diffusion effects of ions. The probability distribution of the CSCP can be obtained by using the statistic approach to analyze the computation results of the stochastic kinetic equation. The model is validated by the experiments performed in the study and in the literature respectively. The results show that the CSCP in concrete at each time step should be treated as a random variable following a certain probability distribution. The discreteness of experimental results can be quantitatively described by the coefficient of variations (CVs) of random variables. The probabilities of experimental results attained by the proposed method can be employed to judge the reliability of data. Furthermore, in order to evaluate the effects of the CSCP on concrete durability, the model can also be used to predict the developing trends of the CSCP, as well as providing their probabilistic information.

The electrolyte renewal effect on the corrosion mechanisms of API X65 carbon steel under sweet and sour environments

Sweet and sour services are the most common media found inside the pipelines of petroleum industry. They are one of the main causes of degradation by corrosion that lead to several financial and environmental losses worldwide. They also are responsible for the formation of corrosion products that might play a protective feature on the metal surface diminishing the corrosive processes. However, conditions in the field are not necessarily favourable for the precipitation of protective structures given the physicochemical dynamism inside the pipes. Then, the need to address this issue that occurs inside the tubes becomes crucial for the correct assessment of the development of protective corrosion products hence to give a more realistic approach to the lab conditions. Therefore, this paper presents a methodology to investigate the electrolyte renewal effects on API X65 carbon steel corrosion under CO2 and H2S (thiosulfate) environments at 4,5 bar of pressure, temperatures of 90 °C and 120 °C over 150 h. Electrochemical techniques (LPR and EIS), weight loss and characterizations were conducted in two different average pH, 3,3 and 4,5. The proposed methodology was capable to delay the development of protective scales in renewed media. The corrosion rates were higher for conditions with electrolyte renewal and higher temperature. FeCO3 formation was favoured at high pH and 120 °C whilst FeS structures were dominant at 90 °C. Sulphides were more cracked and uneven in renewed media whereas carbonate crystals presented higher anchorage to the substrate and were able to develop in sizeable diameters. Unrenewed media presented the best electrochemical responses.

Corrosion rate and mechanisms of a rail head surface under artificial rainwater conditions

The aim of this work is to study the effect of rainwater on the formation of cracks by corrosion process. Inclusions and metallographic analyses, linear polarization resistance, and potentiodynamic anodic polarization tests were carried out. The results present a ferritic network on the external surfaces of the rail head and a large area occupied by inclusions. Linear polarization measurements did not show a reduction in corrosion rate after the corrosion products formation. In conclusion, corrosion by rainwater can develop cracks all over the rail head.

Morphological and corrosion studies of ammonium phosphate and caesium nitrate treated Al coating deposited by arc thermal spray process

In the present studies, the Al coating deposited by arc thermal spraying process was treated with different concentrations of ammonium phosphate mono basic ((NH4)H2PO4) and caesium nitrate (CsNO3) to improve the morphology and corrosion characteristics of the coating. As coated (AC) sample exhibits pores and defects onto the surface but once the treatment was carried out, the coating shows reduction in porosity as observed by scanning electron microscopy (SEM). The treated coatings contain caesium aluminum oxide (CAO: Cs2Al2O3) and ammonium aluminum hydrogen phosphate hydrate (AHP: (NH4)3Al5H6(PO4)8.18H2O) as composite oxides identified by X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS) results reveal that as the exposure periods are increased, the resistance to coating/treatment (Rc/t) and charge transfer resistance (Rct) of AC and 0.5 M NH4H2PO4 and 0.0025 M CsNO3 (CN2) are increased with exposure periods in artificial ocean water solution. The improvement in total impedance values at 0.01 Hz of AC sample is attributed to formation of corrosion products which fill the pores/defects of coating while CN2 sample owing to the treatment film i.e. AHP and CAO and transformation of AHP into stable form. As the amount of NH4H2PO4 and CsNO3 is increased up to 1 M and 0.005 M i.e. CN3, the AHP film dissolved and enhances the corrosion reaction. Thus, cracking is observed in corrosion products. The enhancement in corrosion resistance of CN2 sample is attributed to the formation of α-Al(OH)3 (bayerite) and Al3(PO4)2(OH)3(H2O)5 (Aluminium hydroxide phosphate hydrate: AHPH) in greater amount as corrosion products. These corrosion products of CN2 sample are stable, sparingly soluble and protective.

The Application of Affine/Interval Algebra to Determine the Time of Concrete Cover Damage in Reinforced Concrete Due to Corrosion

This paper presents the application of affine numbers to determine the time of concrete cover cracking in reinforced concrete elements from the initiation of the reinforcement corrosion. This issue is crucial for evaluating sustainability and durability of reinforced concrete structures. The proposed general approach has been used to forecast displacements and crack propagation versus time in reinforced concrete elements subjected to corrosion tests. The affine approach equations describing changes caused by the formation of corrosion products are defined and the corresponding tensor of the volumetric strain rate is formulated. The time of cover cracking has been analysed using the Finite Element Method (FEM) and the Monte Carlo (MC) method to verify the correctness of calculations.

Corrosion behaviors of carbon steel induced by life activities of Phaeodactylum tricornutum in a marine environment

AbstractMicrobiologically influenced corrosion induced by bacteria has been studied for many years. Corrosion is known to be sensitive to the presence of microalgae, such as Phaeodactylum tricornutum. However, the life activity of P. tricornutum that influences the general and localized corrosion of carbon steel is not fully understood. The current study uses a combination of immersion tests and electrochemical experiments with a detailed surface characterization to reveal the naturally formed corrosion products with/without the presence of P. tricornutum. The results show that samples suffer from pitting corrosion and the averaged pit depths are approximately 15 μm under a light–dark cycle condition or a 24‐h constant light condition. Meanwhile, the corrosion products are mainly comprised of γ‐FeOOH and Fe3O4 in a constant light condition. However, γ‐FeOOH, Fe3O4, and FeCO3 are found in a light–dark cycle. This study proposes the fundamental mechanisms of the effect of P. tricornutum life activities on the corrosion performance of Q235 carbon steel, to fulfill the knowledge gaps of the presence of microalgae inducing the general and pitting corrosion of carbon steel.

Brass dezincification with a bipolar electrochemistry technique

A bipolar electrochemistry approach was applied to characterise the dezincification of brass. The dissolution of both Cu and Zn resulted in the formation of Cu2O, CuO, ZnO and CuClx, with corrosion product formation characterised as a function of the potential gradient. At low potentials, protective corrosion products formed, with compositional changes observed via dezincification up to a critical applied potential threshold. Above the critical potential, no corrosion products could form, resulting in higher corrosion rates. The influence of corrosion product formation after bipolar electrochemistry assessment is compared to results from standard three-electrode potentiodynamic polarisation tests.

The corrosion of mild and stainless steel in alkaline anaerobic conditions representing the Belgian “supercontainer” concept and the Swiss L/ILW repository

AbstractDeep geological repositories for radioactive waste contain metallic materials, either used to construct disposal canisters or as low‐/intermediate‐level waste (L/ILW). The safety relevance of corrosion is linked to canister lifetime in the former case and gas generation in the latter. More specifically, the Belgian “supercontainer” concept envisages mild steel for the used fuel disposal canister, and in the case of the Swiss L/ILW repository, mild steels are the largest metallic waste component due to the decommissioning of civilian power‐generating facilities. For these circumstances, the corrosion environment is dominated by the chemistry of cement, which is used as buffer or backfill material. The corrosion behaviour of mild steel in anoxic environments was studied through the analysis of the hydrogen end‐product. Hydrogen analysis was conducted by periodically purging the cell head‐space and analysing the gas using a solid‐state hydrogen sensor. While this method is limited to providing only uniform corrosion rates averaged over periods of time, ranging from weeks to months, it provides excellent resolution and sensitivity. The test cell environments were matched against the anticipated Belgian high‐level waste and Swiss L/ILW repository environments, and also against experiments that have been conducted by other researchers for comparative purposes. Samples were exposed to synthetic cement pore waters, representing fresh and degraded cement. In young cement waters, the formation of initial corrosion products resulted in steel wire corrosion rates of the order of µm/year, which, at 80°C rapidly declined to ∼10 nm/year. In contrast, SA516 grade 70 steel plate corroded much more slowly under similar conditions. In aged cement waters, initial corrosion rates were higher but declined faster towards a longer‐term rate of ∼10 nm/year. 316L stainless steel, embedded in cementitious material, corroded at a rate of <1 nm/year at 50°C.

Electrochemical Characterization of an Oil/Water Alternately Wetted Rotating Cylinder Electrode

To characterize the corrosion at oil/water interfaces, a vertically adjustable rotating cylinder electrode (VA-RCE) was developed based on the concept of an “alternate wetting cell,” in which the electrochemical current reflecting the wet state of the RCE surface can be continuously monitored. Under a sinusoidal moving mode, the current waveform varied with the rotation rate and the longitudinal displacement speed or amplitude of the VA-RCE, implying that the dynamic wetting behavior of the VA-RCE surface in the oil/water interface region was influenced by the flow conditions; the replacement of oil phase by water phase became easier with increasing flow rate and alternating frequency of change between water wet and oil wet. The results also indicated that the wettability of the VA-RCE surface could be modified by the formation of corrosion products. All of the results suggested that the VA-RCE could be used to quantitatively characterize the dynamic water/oil wetting state and the corrosion at an oil/water interface in a multiphase flow.

Analysis and Prediction of Corrosion of Refractory Materials by Sodium Salts during Waste Liquid Incineration-Thermodynamic Study.

Incineration of high-content sodium salt organic waste liquid will corrode the refractory material in the incinerator, causing the refractory material to peel off and be damaged. A thermodynamics method was used to study the thermodynamic properties of three common sodium salts (NaCl, Na2CO3 and Na2SO4) on the corrosion of refractory materials (MgO·Cr2O3, MgO·Al2O3, Al2O3, MgO and Cr2O3). The results determined that MgO has the best corrosion resistance and is not corroded by the three sodium salts. On this basis, the thermodynamic corrosion experiments of NaCl corrosion of magnesium oxide at three temperatures of 600, 1000 and 1200 °C were carried out. Analysis of the corrosion product by X-ray diffraction (XRD) showed no corrosion product formation. Studies have shown that thermodynamic calculation can accurately predict the thermodynamic mechanism of alkali metal corrosion to refractory materials, and MgO is a good anti-alkali metal corrosion refractory material.

Particularities of indoor atmospheric corrosion of steel inside electric boxes in the tropical climate of Tabasco, Mexico

Indoor corrosion inside electric boxes is important for the reliability of electric and electronic instruments. A parallel evaluation of indoor/outdoor atmospheric corrosion of steel, pollutants and meteorological parameters was made at two sites, i.e. a rural site and a coastal site of the Tabasco State, Mexico. Two exposure conditions were evaluated: outdoors and inside electric boxes. Very low levels of sulphur compounds have been observed at the two exposure sites and two exposure conditions. As expected, corrosion of steel in an open atmosphere is higher than indoors (electric boxes). The difference between corrosion outdoors and inside electric boxes is higher at the coastal site due to the influence of chloride deposition. Significant differences have been observed in the morphology of corrosion products formed on steel. The influence of sun radiation, rain, dew and fog causes the formation of more compact corrosion products. The influence of Time of Wetness outdoors is in some extent equivalent to the influence of relative humidity inside electric boxes. Commonly, chloride deposition is very low indoors, showing low influence on corrosion. However, in particular conditions of Tabasco coastal tropical climate, its role is significant indoors. Reliability of electric and electronic instruments could be affected.

Investigation of the accumulation of alloying elements (Mn, Ni, Mo) on the surface of high-alloy steel in acid medium

The formation of corrosion products in the surface layers of steel 15KH12VNMF brand was investigated in solutions of hydrochloric, sulfuric, phosphoric, and nitric acids. Comparative data were obtained on the accumulation of impurity alloying elements in surface layers of high-alloy steel 15KH12VNMF brand. The content of alloying elements was defined in the surface layer of steel and corrosion products when holding samples in solutions with a certain concentration for 1 hour. The obtained data indicate that the accumulation of manganese, molybdenum and nickel in the surface layer does not occur in the sulfuric acid solution. The surface layers in the solution of phosphoric acid accumulate intensively alloying impurities, whereas in nitric and hydrochloric acids there is a selective accumulation. The surface films on the steel 15KH12VNMF brand in solutions of hydrochloric, sulfuric, phosphoric, nitric acids were Identified at high concentrations and times of incubation. It was established that the rate of manganese accumulation in hydrochloric acid is constant, regardless of the acid concentration. For nickel and molybdenum, the rate of accumulation increases at initial concentrations, and tends to its constant value at high concentrations. In sulfuric acid solutions, the amount of manganese on the surface depends not only on the concentration, but also on the holding time. The accumulation of nickel and molybdenum on the surface of the plate depends as on the concentration and the time. It was determined that in solutions of phosphoric acid the accumulation of manganese occurs only at the primary time, in the future remains constant. The accumulation of nickel and molybdenum on the surface depends as on the concentration and the time and has a similar character. The data are obtained that the accumulation of manganese, nickel, molybdenum on the surface of the sample in solutions of nitric acid with increasing concentration occurs regardless of the holding time of the sample.

Investigation of Mild Steel Corrosion in the Cement Production Associated with the Usage of Secondary Fuels

The present work deals with the corrosion of mild steel (1.0037) used as the outer construction material of the preheater of a modern industrial cement production facility. The facility uses secondary fuels, which introduce considerable amounts of corrosive species. The situation at the examination sites in the preheater zone is tracked over a period of two years including operation and shut-down periods. The investigation is focused on (i) the acquisition of the underlying physicochemical conditions, such as moisture, temperature, and contamination data at the examination site of the preheater, (ii) the multianalytical identification of the formed corrosion products using scanning electron microscopy combined with energy-dispersive X-ray analysis, infrared spectrometry, Raman spectrometry, X-ray diffractometry, and Möβbauer spectrometry, and (iii) voltammetric and EIS laboratory investigations using model solutions. It was evidenced that corrosion takes place at a temperature level of about 100°C in the presence of moisture and oxygen as well as chloride ion as a consequence of the usage of secondary fuels. Typical hot-gas corrosion could be excluded under the current conditions. Appearance, structure, and nature of the corrosion products were found to be not mainly dependent on the varied length of exposure, but on the conditions of the hosting preheater intake. In addition to different FeOOH phases and hematite, magnetite was found, dependent on the oxygen concentration in the process gas. The decisive role of oxygen as key factor for the corrosion rate was electrochemically confirmed.

Aspects on Early-Stage Corrosion of Different Zinc Alloys: Wet scCO2-Induced Corrosion

The surface activity of different zinc alloys was evaluated in wet scCO2. The zinc coating surface chemistry governed the corrosion product formation. On zinc and Zn-Al coatings, the Al2O3 layer prevented growth of corrosion products. A Zn-Al-Mg coating showed high initial reactivity due to active Zn-Mg phases. An electrogalvanized coating was very active due to a high ratio of exposed, less dense planes. In a Zn-Fe coating, several Zn-Fe phases were susceptible to wet scCO2 at the same time, triggering the sacrificial effect of Zn. Wet scCO2 is a convenient medium to assess the early-stage corrosion of metal coatings.

Improvement of Mechanical and Anticorrosion Coating Properties in Conducting Polymer Poly(Propyl Methacrylate) Embedded with Silane Functionalized Silica Nanoparticles

An excellent new nanocomposite coating consisting of poly(propyl methacrylate) (PPMA), silanes and SiO2 nanoparticles (i.e., PPMA/silane/SiO2 blend) for aluminium alloy (AA7178) protection in natural seawater is investigated by electrochemical techniques. Three different silanes namely, ethyltriethoxysilane (EES), (3-glycidyloxypropyl)triethoxysilane (GES), and (3-aminopropyl)triethoxysilane (AES) were used to prepare functionalized SiO2 nanoparticles which are incorporated into PPMA to form PPMA/EES/SiO2, PPMA/GES/SiO2, and PPMA/AES/SiO2 nanocomposites. Electrochemical impedance spectroscopy (EIS) displayed a pronounced increase in the charge transfer resistance and potentiodynamic polarisation studies showed a significant decrease in the corrosion current for the investigated nanocomposites. The resultant nanocomposites performed as an excellent passivation layer which prevents the diffusion of ions and slows down the corrosion process due to the inclusion of silane functionalized SiO2 nanoparticles to PPMA. Scanning electrochemical microscopic (SECM) studies showed very lower corrosion current at the scratch of the PPMA-silane/SiO2 nanocomposite coated aluminium alloy. Field emission-scanning electron microscopy/energy dispersive X-ray (FE-SEM/EDX) analysis displayed the formation of corrosion products as the passive layer that hinders the dissolution of aluminium alloy. Mechanical properties of the coated aluminium alloy were found to be enhanced by the inclusion of functionalized SiO2 nanoparticles to PPMA which complimented the electrochemical studies.

In-situ EIS study on the initial corrosion evolution behavior of SAC305 solder alloy covered with NaCl solution

The corrosion performance of SAC305 solder joints is closely related to the working efficiency and life-span of electronic devices. Available studies on corrosion of SAC305 solder have seldom concentrated on its initial corrosion evolution behavior, which is critical in understanding its corrosion behavior in the long run. In this work, comb-like electrodes have been designed for in-situ EIS measurements to investigate the initial corrosion evolution process of SAC305 solder covered with 3.5 wt.% NaCl solution, and Raman, XRD, SEM and EPMA have also been employed to characterize the formed corrosion product layer. The results indicate that the initial corrosion evolution behavior of SAC305 solder mainly involves four stages, i.e. the corrosion degradation of the pre-existing SnO2 protective film in a short duration in contact with NaCl solution, the anodically dissolved Sn2+ undergoes hydrolysis under the effect of Cl− in electrolyte to form stannous hydroxychloride intermediates of various structures, the formation of Sn3O2(OH)2 from stannous hydroxychloride intermediates after Cl− releasing, and finally the formation of nano-SnO2 particles from Sn3O2(OH)2 after steps of dehydration and oxidation. Meanwhile, the acidified NaCl electrolyte can make the formed SnO2 slightly dissolved and favors the formation of SnCl4·4H2O crystals. These findings clearly demonstrate the initial corrosion evolution behavior and corrosion product formation mechanism of SAC305 solder, and are expected to provide potential guidelines on maintenance of microelectronic devices in marine atmosphere.

Spent fuel corrosion and the impact of iron corrosion – The effects of hydrogen generation and formation of iron corrosion products

Canister designs for deep geological disposal of spent nuclear fuel typically involve large amounts of iron. Canister failure will likely involve corrosion of the canister at the disposal depth several hundred meters underground, where conditions are typically anoxic. Spent nuclear fuel corrosion and dissolution will therefore likely proceed together with anoxic iron corrosion. The iron corrosion can suppress spent fuel corrosion by creation of strongly reducing conditions from Fe(II) formation and generation of large quantities of hydrogen. In an attempt to separate the effect of hydrogen from that of Fe(II) and iron corrosion products, two experiments were performed. In both cases, spent nuclear fuel powders were used in autoclaves filled with simplified granitic groundwater initially pressurized with argon. In the first experiment, the autoclave contained iron powder. Following the initial radionuclide release at start-up, the concentration of redox sensitive radionuclides decreased with uranium reaching UO2 (am) solubility levels within months. Release of non-redox sensitive elements such as Cs ceased after 223 days. Continuous hydrogen generation was observed. XRD and Raman spectroscopy of the iron corrosion products identified magnetite. The second experiment was therefore performed starting with magnetite powder. In this case, the autoclave argon atmosphere remained constant. Radionuclide release was, however, continuous with uranium reaching >2 × 10−5 M after 275 days. The magnetite powder of the second experiment was analyzed and found to be composed of mainly magnetite with a small fraction of hematite. In the iron corrosion experiment, Mo, Tc and U where found to have high iron corrosion product affinities. However, in the magnetite experiment, U, Tc and Mo displayed weak affinity for the corrosion products, indicating presence in the higher oxidation state. The results thus point to hydrogen evolution being the main contributor to the apparent inhibition of radionuclide release in the iron corrosion experiment.

CO2 Corrosion of Carbon Steel: The Synergy of Chloride Ion Concentration and Temperature on Metal Penetration

This paper investigates the synergy of chloride ion concentration and temperature on the general and pitting corrosion of carbon steel in CO2-saturated environments. Experiments were conducted over 168 h in different concentrations of NaCl brines (1 wt%, 3.5 wt%, and 10 wt%) and temperatures (30°C, 50°C, and 80°C) with the aim of elucidating the combined effect of changes in chloride ion concentration and temperature on overall metal degradation, taking into consideration general and pitting corrosion. This also includes a correlation with the formation and properties of FeCO3 corrosion products. Linear polarization resistance was implemented to monitor the electrochemical responses. Corrosion product characteristics and morphologies were studied through a combination of scanning electron microscopy and x-ray diffraction. Pitting corrosion evaluation was conducted through the application of 3D surface profilometry to study pit geometries such as the depth and diameter. The results show that general and pitting corrosion are strongly correlated to the synergistic effects of changing chloride ion concentration and temperature in carbon steel as a result of their combined influence on ferrite (Fe) dissolution and FeCO3 formation. This represents a paradigm shift from the already established mechanisms on chloride ion and temperature effects on passive alloys such as stainless steel. Increasing chloride ion concentration and temperature up to 10 wt% NaCl and 50°C to 80°C, respectively, is observed to increase the rate of Fe dissolution and formation of semiprotective FeCO3 corrosion products, leading to the increased manifestation and severity of pitting corrosion. The results also show that a “threshold chloride concentration” exists at 30°C, above which there is no significant increase in corrosion rate. However, such “threshold effects” were not observed at higher temperatures evaluated in the range of chloride concentration considered in this study.

Corrosion behavior of immersion silver printed circuit board copper under a thin electrolyte layer

The corrosion behavior of immersion silver printed circuit board copper (PCB-Cu-ImAg) under a thin electrolyte layer (TEL) was studied by electrochemical tests and surface analysis. The results showed that galvanic effect accelerated the corrosion of PCB-Cu-ImAg and reduced the protective effect of silver-coating. The reduction of TEL thickness not only promoted the corrosion of PCB-Cu-ImAg, but also strengthened the galvanic effect. At the beginning of exposure to TEL, the potential difference decreased, but the galvanic current densities increased with decreasing TEL thickness because of the significant decrease of the total resistance. Because of the continuous formation and accumulation of corrosion products, the galvanic current densities decreased in the later stage of exposure to TEL.

Dynamic Corrosion Trail of Ti-6Al-4V Alloy in Acid Artificial Saliva Containing Fluoride Ion

The dynamic corrosion behaviors of Ti-6Al-4V alloy in acid artificial saliva containing fluoride ion were traced using electrochemical techniques, optical microscope, scanning electron microscopy, energy dispersive spectrometer and roughness tester. The experimental results indicate that a negative shift of corrosion potential as well as a continuous decrease in impedance for the alloy exists with increasing immersion time, and the degradation rate of the alloy presents the trend of first increase then decrease following the dissolution of passivation film and the formation of corrosion products. The accumulated fluoride ion on the alloy surface accelerates the fracture of passivation film, and the occurrence and development of corrosion of alloy are mainly located at the sites where the formation and shedding of white particles are composed of fluoride compounds, resulting in the decrease of corrosion resisting property of the alloy. A possible model is proposed to elaborate the dynamic corrosion behavior of the alloy.