Accelerated Corrosion Tests Research Articles

Chromium-Free Conversion Protective Coatings on 1424 Aluminum Alloy

Abstract—It is known that lithium-containing aluminum alloys possess low pitting corrosion resistance. It has been previously shown that an IFKhANAL-3 alkaline chromate-free conversion composition gives the coatings on a series of aluminum alloys, such as AMg3, D-16, and V95, which are comparable to conventional chromate coatings in terms of protective properties. It should also be noted that inhomogeneous CCs that do not adhere to the substrate are formed in standard chromate conversion composition on lithium-containing alloys; therefore, development of the method for the fabrication of protective CC for 1424 alloy is a relevant task. In this work, the effect of various complexing agents on the oxidation and protective properties of the coatings based on 1424 alloy have been studied. The modifying additives under study have decreased the concentration of different oxides in the conversion compositions providing adsorption of corrosion inhibitors and increase in their protective properties. According to the results of accelerated corrosion tests, integrated use of Trilon B and BTA significantly increases the corrosion resistance of the coatings based on 1424 alloy.

A Cracking Model for Reinforced Concrete Cover, Taking Account of the Accumulation of Corrosion Products in the ITZ Layer, and Including Computational and Experimental Verification.

The paper presents the finite element method model (FEM) which allows the forecasting of the evolution of damage in a concrete cover together with experimental verification of the model. The objective of the model is to define the corrosive volume strain tensor rate effected by corrosion, which comprises the accumulation of corrosion products in pore spaces as well as in micro-cracks which develop at the initial stage of cover degradation. The propagation of damage in the contact zone was captured by taking into account the function describing the degradation of the interface transition zone depending on the cover tightening time–critical time. The method of determining the critical time along with the method of taking into account the effective electrochemical equivalent of iron was also analyzed in this paper. The work presents the experimental verification of the model using an accelerated corrosion test of reinforcement in concrete and strain measurements with optical methods. The conducted tests demonstrate satisfactory compliance of the model with the test results.

Research on the Chloride Ion Penetration Resistance of Magnesium Phosphate Cement (MPC) Material as Coating for Reinforced Concrete Structures

This study focuses on the chloride ion penetration resistance of a magnesium phosphate cement (MPC)-based composite material coating on the surface of silicate material. By means of electrical flux method and electric acceleration corrosion tests, the anti-chlorine ion permeation and reinforcement properties of MPC-based materials and Portland cement (OPC) mortar were compared and analyzed. The experimental results show that the electrical flux of the hardened body of the MPC-based material is much lower than that of the Portland cement mortar, and the electrical flux of the hardened body of the MPC mortar can be obviously reduced by adding silica-fume (SF) and fly ash (FA), which, when combined in a suitable proportion, will make the MPC’s hardened body more dense and impermeable. The addition of short cut fibers increases the number of pores, the pore size, and the electrical flux of the cement mortar’s hardened body. The adverse effects of the three fibers on the permeability of the MPC mortar against chlorine ions were as follows: polyvinyl alcohol fiber > glass fiber > basalt fiber. The electrical flux of MPC mortar or MPC paste coated on the surface of the OPC mortar was greatly reduced. Compared with silicate mortar, the MPC-based material has excellent protective performance under the condition of accelerated corrosion.

(Keynote) Sensor Design, Construction and Validation for in-Situ Water Layer Thickness Determination during Accelerated Corrosion Testing

The design, construction, validation, and application of a sensor to determine water layer (WL) thickness in the range of 0 to 5 mm in salt spray testing using finite element modeling (FEM) and experimental methods is presented. The sensor determines WL thickness based on electrical resistivity, which is a function of the width of the sensor, distance between the electrodes, and solution conductivity. Sensor design, and validation under known WL thicknesses, was informed by FEM results. The utility of the sensor was shown by measuring WL thickness in a continuous salt spray test similar to ASTM B117 (3.5 wt % NaCl at 35 ˚C) and the range of specifications allowed within the standard were explored. Within the realms of accelerated corrosion testing, the angle of exposure played the largest role in WL thickness. Furthermore, it was found that above an angle of 20˚ from vertical the WL experiences semi-periodic run-off events causing a transient decrease in the WL by up to 80%. Finally, the angle of sample exposure in salt spray environments determines if thin film conditions are achieved, influencing the rate of corrosion. The large allowances for sample angle present in most standards for laboratory corrosion chamber testing pose a large source of test-to-test and chamber-to-chamber variability. Acknowledgements SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. This document is SAND2020-5133 A

Corrosion Resistance of Electrochemically Exfoliated Doped-Graphene Nanostructures

Graphene with its high conductivity and accessible surface area makes it an ideal material applicable as an adsorbent that can be electrochemically regenerated and reused over several cycles. However, it has been reported that corrosion causes degradation, weight loss and lifetime reduction of these adsorbents [1]. Most studies on corrosion mechanism in carbon materials has focused on highly porous and disordered materials used as catalyst supports for fuel cell electrodes. However, little work has been done to identify the corrosion mechanism in doped-graphene materials. The current study analyzes the corrosion resistance by using an accelerated corrosion protocol on electrochemically synthesized graphene samples with different doped heteroatoms including nitrogen and phosphorus. The accelerated corrosion protocol consisted of a potential steps whereby graphene was exposed to high potential for a few seconds for carbon corrosion to occur [2]. The corrosion mechanism and the degree of oxidation of the doped-graphene materials were characterized using cyclic voltammetry (CV), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Electroactive groups, changes in the double layer capacitance, and morphological changes were identified using these techniques. The stability of samples was determined for different samples using the accelerated corrosion test. Interestingly, the peaks associated with electroactive oxygen-containing surface groups were present and showed the extent of corrosion for both graphene samples before and after the test. A higher degree of corrosion was observed from the phosphorus doped-graphene as compared to the nitrogen-doped graphene. This was further confirmed from the corrosion current and percentage change in gravimetric capacitance. The implication of these findings suggest that the large distortion caused by the additional P-doping in the carbon lattice allows open edge sites and produces wrinkles [3]; thus providing more defective sites and facilitating corrosion. Further materials analyses are ongoing to fully elucidate this process in detail and support the results obtained from the electrochemical tests.

A Study on the Location of the Cathode in Galvanic-Induced Crevice Corrosion

Fastener-in-panel systems are commonly used in aerospace construction. The geometries are very complicated, especially in the context of corrosion. Generally, fasteners are made of more noble materials, such as stainless steels, due to their good mechanical properties. Panels can represent the structural components of an aircraft, which are generally built with aluminum alloys, due to their high strength-to-weight ratio. The combination of these two metals when in electrolytic contact, as could occur from a light rain or morning dew, makes the system susceptible to galvanic corrosion. The fastener also forms an occluded region within the panel, adding in the possibility of crevice corrosion. Furthermore, aircraft are often exposed to cyclic wet and dry environments, leading to an atmospheric water layer which can exacerbate corrosion.The complicated and interacting mechanisms involved in the fastener/panel design have been investigated through finite element modeling (FEM) in this work. FEM has been advancing in recent years, and specifically has become a useful tool in studying galvanic corrosion [1]. The complexities surrounding a fastener-in-panel system are difficult to isolate individually experimentally. Modeling allows deconvolution of the specific parameters, efficiently assessing the effects and isolating changes in parameters in a way that is not possible experimentally.Previous work has compared experimental analysis with FEM in a large-scale fastener geometry [2]. This paper describes a similar investigation, with a more prominent focus on the fastener hole. Specifically, galvanic-induced crevice corrosion was studied in order to determine which location on the cathode was producing the main driving force. Therefore, the geometry was representative of a cross-section of one fastener installed in a panel, in order to negate the interaction of multiple fasteners. Knowledge of the location driving the cathodic reactions would aid in finding mitigation strategies for crevice corrosion, such as whether coating the head of the fastener or the shaft of the fastener is more important.Different locations of the active cathode were tested systematically, such as variations between an inert fastener shaft (that is, the crevice former) or an active shaft coupled with an inert or active fastener head. The transport of aluminum ions was tracked within the model as well. Both steady-state and time-dependent models are described, in order to determine if the cathode inside of the fastener hole acts as a driving force before being stifled through the production of hydroxyl.SS316 and AA7075 are the materials of focus for the fastener and panel, respectively. SS316 has been shown to form a severe galvanic couple with AA7075 [3], leading to the formation of intergranular corrosion fissures of 2mm in length inside of the fastener hole [2]. A sol-gel coated SS316 fastener was also investigated, to determine the level of mitigation achieved. Boundary conditions for these materials were generated experimentally, through potentiodynamic scans.[1] C. Liu and R. G. Kelly, “A Review of the Application of Finite Element Method (FEM) to Localized Corrosion Modeling,” CORROSION, 2019.[2] R. S. Marshall, R. Kelly, A. Goff, and C. Sprinkle, “Galvanic Corrosion Between Coated Al Alloy Plate and Stainless Steel Fasteners, Part 1: FEM Model Development and Validation,” Corrosion, vol. 75, no. 12, pp. 1461–1473, 2019.[3] C. A. Matzdorf, W. C. Nickerson, B. C. Rincon Tronconis, G. S. Frankel, L. Li, and R. G. Buchheit, “Galvanic test panels for accelerated corrosion testing of coated al alloys: Part 1 - Concept,” Corrosion, vol. 69, no. 12, pp. 1240–1246, 2013.

Monitoring internal corrosion in steel pipelines: a two-step helical guided wave approach for localization and quantification

This article presents a two-step approach for the assessment of internal corrosion in cylindrical structures using helical guided ultrasonic waves. The approach consists of two steps such as (1) localization and (2) estimation of the size of the corroded area. Localization is performed with the algebraic reconstruction technique where the energy ratio of the two fundamental Lamb modes S0 and A0 is used as input damage coefficient. Using the output of the localization step, the size of the corroded area is estimated by iteratively solving the eikonal equation using a finite-difference approach. The proposed approach is validated by an accelerated corrosion test. Furthermore, numerical simulations are carried out to study the interaction of the energy ratio and the phase velocity travel time with various thickness profiles acquired from the experiment. The proposed approach is validated against the experimental data up to approximately 50% thickness loss.

Bond-slip behavior between corroded I-shaped steel and concrete in a subsea tunnel

Owing to the high chloride ion content in the service environment, corrosion of I-shaped steel in the primary support of subsea tunnels is inevitable; this leads to the degradation of bond performance between I-shaped steel and concrete and seriously affects the durability of subsea tunnel support systems. However, the bond-slip behavior between concrete and corroded I-shaped steel may be different from that occurring in reinforcement concrete (RC) and ordinary steel reinforcement concrete (SRC) structures for two main reasons: (1) the contact area between the I-shaped steel and concrete is larger and the shape of the I-shaped steel cross-section is more complicated than that of steel bars; (2) compared with ordinary SRC structures, those in a tunnel have no stirrup without considering shear resistance. The main objective of this study was to study the effect of corrosion on the bond-slip behavior between I-shaped steel and concrete. First, accelerated corrosion tests and push-out tests were conducted on SRC specimens and the failure mode and bond-slip curves of the specimens were investigated. The experimental results indicated that the failure mode of the experimental specimens was mainly splitting failure. Meanwhile, a three-stage bond-slip constitutive model for concrete and corroded I-shaped steel was proposed, which correlated well with the experimental curve. Finally, the degradation process of interface bond-slip caused by corrosion was analyzed via the energy principle. The dissipated energy ratio increased and the elastic energy ratio gradually decreased with increasing corrosion rate, indicating that the greater corrosion rate of I-shaped steel led to more serious internal damage. Furthermore, the damage variable was defined by the dissipated energy ratio evolution characteristics. The damage evolution models of the bond strength eigenvalues and the characteristic slip were established, which was in good agreement with the experimental data.

Bond strength of corroded reinforcements in concrete after high-temperature exposure

Reinforcement corrosion is common in concrete structures subjected to chloride exposure. The bond behaviours between corroded reinforcements and concrete after high-temperature exposure are important in the fire damage assessment of aging concrete structures. The effects of reinforcement corrosion on the bond behaviour between concrete and reinforcements after high-temperature exposure is investigated in this paper. Corroded pull-out specimens were prepared using accelerated corrosion tests. These corroded specimens were heated in an electric resistance furnace and then subjected to pull-out tests. The test results showed that the failure mode of the pull-out specimen was affected by the degree of steel corrosion, the temperature experienced, concrete cover depth and stirrup usage. The bond behaviour was less influenced when the degree of corrosion was less than 0.05 or when the exposure temperature was less than 200 °C. The bond strength reduced significantly when the temperature was between 400 and 600 °C or when the corrosion degree was greater than 0.05. The concrete cover depth and stirrup usage also had an obvious effect on the bond strength after exposure to different temperatures, whereas these parameters had little influence on the bond strength when the experienced temperatures exceeded 600 °C. Finally, a calculation method for bond strength was proposed considering the corrosion degree and temperature.

Spray fabrication of superhydrophobic coating on aluminum alloy for corrosion mitigation

A novel superhydrophobic coating was fabricated by spraying with F-SiO2 nanoparticles, epoxy resin adhesive, fluorosilicone varnishes and white fluorinated polyurethane coatings. The wettability, surface roughness, surface morphology and surface chemical group of superhydrophobic coating were characterized. Mechanical stability, corrosion resistance and self-cleaning ability of superhydrophobic coating were examined. Results showed that superhydrophobic coating exhibited excellent water-repellency. The contact angle of superhydrophobic coating was 161.35° and the sliding angle was only 2.0°. The contact angles of superhydrophobic coatings after 20 continuous abrasion cycles, 1.5 h water dripping or 20 tape peeling cycles were all above 150°. Superhydrophobic coating had a significant enhancement in corrosion resistance. The corrosion potential and corrosion current density of coating after 20 d neutral salt spray accelerated corrosion test were -0.54 V and 5.26 x 10−8 A cm-2, respectively. Sand adhered to superhydrophobic coating could be easily washed away, which revealed superhydrophobic coating exhibited excellent self-cleaning ability.

Finite Element Simulation of Steel Column Considering Corrosion Morphology

This paper carries out the three-dimensional scanning and eccentric compression bearing capacity test of a corroded steel column, which is obtained from the artificial accelerated corrosion test, and through the finite element software, establishes a finite element model considering the true corrosion morphology of the compressed flange and the web to study the effect of corrosion on the ultimate bearing capacity of steel column. The research result shows that the surface of rusted steel is rough, and the stress distribution is uneven. The maximum stress point is often occurred at the bottom of the rust pit, and there is stress concentration at the rust pit. Corrosion causes a significant reduction in the bearing capacity of the steel column. The numerical analysis method considering corrosion morphology can accurately predict the failure mode and ultimate bearing capacity of eccentric compression corroded steel column.

WITHDRAWN: Performance evaluation of sensors for corrosion monitoring

Reinforcement corrosion in concrete affects the strength and reliability of reinforced concrete structures. The repair and restoration of corroded buildings are uneconomic. Monitoring and maintaining concrete structures during their service life will avoid the ingress of corrosion at the initial level. In this paper, proximity sensors, pH sensors, and temperature sensors were developed and manufactured to track the corrosion potential of the reinforcement in M25 grade concrete. These sensors are used to track the surface of the reinforced concrete specimen in electrochemical studies. A 3.5 percent NaCl accelerated corrosion test is conducted in the marine environment. The capacity of the sensor is tested based on induction and pH values at different stages during the test period. The results are obtained in terms of current flow and induction value, which indicates the sensing capability of a relevant and accurate result.

Effect of glass fiber sheet in adhesive on the bond and galvanic corrosion behaviours of CFRP-Steel bonded system

Steel structures strengthened with CFRP composite may have potential galvanic corrosion issue. It was recommended that a layer of glass fiber sheet (GFS) be embedded in the adhesive layer to protect the CFRP-steel bonded system against galvanic corrosion. But the inclusion of GFS in the adhesive may negatively affect the bond behaviour between steel and CFRP. This paper investigated the effects of GFS on the corrosion behaviour and bond characteristics between steel and CFRP. Three types of experimental testing on CFRP-steel double strap joints with/without GFS were conducted, including accelerated corrosion testing, static and fatigue testing. Accelerated corrosion testing was carried out to justify the effectiveness of GFS in preventing galvanic corrosion of CFRP-steel bonded system. Static tension testing and fatigue testing were carried out to quantify the effect of GFS on the static and fatigue bond behaviour between steel and CFRP. The effects of GFS on the corrosion rate, failure mode, joint capacity and fatigue life were reported. Experimental results suggested that GFS may reduce the fatigue performance of the bond between steel and CFRP, although GFS may slightly improve the static bond behaviour. It is recommended that GFS can be included in the adhesive layer as an additional protection against the galvanic corrosion hazard in the CFRP-steel bonded system, provided that the system has no concern of fatigue loading.

Study of operating properties of aanticorrosion packing papers

Metal products are subjected to atmospheric corrosion during transportation and storing. An important way to prevent this negative phenomenon is application of special packing materials, in particular materials, containing volatile inhibitors of corrosion, which protect metal against various corrosion agents. To protect metal effectively it is necessary to provide a definite level of operating characteristics of packing materials. The purpose of the work was the study of operating properties of inhibited crepe, inhibited and laminated polyethylene film, inhibited crepe and reinforced by polypropylene web papers, manufactured by OJSC “PP TechnoKhim”, Magnitogorsk, used for packing of metals. Structural and dimensional, sorption, deformation and strength characteristics, of the studied anticorrosion papers are presented, the characteristics being calculated based on the results of measurements. To determine their physical-mechanical and anticorrosion properties, standard methods and methodologies were used. To evaluate impact of moisture and transportation conditions, indices of water adsorption and wear of the studied papers were determined. Inhibitor content in these materials was determined by thermogravimetric analysis method. Their protective ability was studied on samples of low carbon steel strip. For accelerated corrosion tests the strip samples were degreased by alcohol, dried in air and packed in the studied anticorrosion papers, after that they were exposed under increased temperatures and moisture conditions. It was determined, that among the materials under the study, the inhibited crepe paper, reinforced by polypropylene web, hhas the best complex of physical-mechanical and anticorrosion properties. It provides a higher level of prevention corrosion of metal l and surpasses other materials in a number of deformation and strength characteristics. Recommendations were proposed to improve qquality of produced anticorrosion papers.

Development of an active/barrier bi-functional anti-corrosion system based on the epoxy nanocomposite loaded with highly-coordinated functionalized zirconium-based nanoporous metal-organic framework (Zr-MOF)

For the first time, the UIO-66, NH2-UIO, and NH2-UIO particles covalently functionalized by Glycidyl Methacrylate (GMA@NH2-UIO), were utilized as the novel functional anti-corrosive fillers. The functionality, high surface area, phase composition, excellent thermal properties as well as chemical stability of the Zr-MOFs were proved by FT-IR, BET, XRD, TGA, and water stability tests, respectively. The smart pH-sensitive controlled-release activity of the corrosion inhibitors (i.e., Zr ions and organic compounds) from the prepared Zr-MOFs was proved by the water stability test of the Zr-MOFs particles in the acidic (pH = 2), neutral (pH = 7.5), and alkaline (pH = 12) solutions containing 3.5 wt% sodium chloride. The active inhibition properties of the Zr-MOFs were obtained in saline solution by two methods of (i) the solution phase and (ii) scratched epoxy coated samples containing Zr-MOFs by Tafel polarization method and EIS analysis. According to the EIS data, the excellent barrier (passive) properties of the composite film filled with GMA@NH2-UIO particles (G-UIN/EP) were proved by the highest impedance level at the lowest f (frequency) (log (|Z|10 mHz = 9.86 Ω.cm2), the lowest value of the breakpoint frequency (log (fb) = −1.42 Hz) and the highest coating undamaged index (85.93%) after 120 h of immersion. The salt spray (accelerated corrosion test) test (SST), pull-off (testing the strength of adhesion), and cathodic disbonding test (CDT) experiments showed excellent interfacial-adhesion properties of the G-UIN/EP sample in two dry (unexposed) and wet conditions. The hardness test showed that through the incorporation of the UIO, UIN, and G-UIN particles into the epoxy coating, the hardness, and scratch-resistance of the coating were notably improved.

Tratamientos Térmicos y Corrosión en Niebla Salina en acero inoxidable AISI 316L

En este trabajo se evalúa el comportamiento microestructural de un acero inoxidable AISI 316L, tratado térmicamente y sometido a ensayos de corrosión acelerada, durante 96 horas, en cámara de niebla salina según normas ASTM B117 e ISO 9227. Se destaca que este material tratado térmicamente y enfriado en aire fue el que presentó mayor grado de corrosión, hallándose relación directa entre las partículas de carburo de cromo y la presencia de grietas asociadas con los productos de la corrosión.

Role of red mud as a cementing material in concrete: a comprehensive study on durability behavior

Red mud (RM), a semi-solid residual of the alumina refinery process, has higher alkalinity, and its disposal leads to environmental imbalance. To overcome this issue, RM is partially replaced with cement in the range of 0% to 20% at an interval of 5%. The present research work majorly focused on durability and micro-level concrete studies containing pre-calcined (600 °C in 2 h) RM. The tests on red mud concrete, viz. compressive strength, sorptivity test, open porosity test, rapid chloride penetration test, accelerated corrosion test, water absorption test, X-ray diffraction, scanning electron microscope (SEM), and energy-dispersive spectroscope (EDS) analysis, have been conducted to investigate the comprehensive characterization of concrete with RM. From the compressive strength test results, maximum strength was observed at 10% replacement. Open porosity, chloride ions permeability, water absorption, and sorptivity values showed reduction at an increment of RM replacement level. RM concrete offered more corrosion resistance due to high alkalinity, which possessed a pH of more than 12.5. From the micro-level investigations such as SEM and EDS, higher C–S–H gel formation was observed in RM 10% replacement concrete. In the meantime, less number of pores was observed in all RM replaced concrete mixes.

Electrochemical Corrosion of SAC Alloys: A Review

Tin–silver–copper (SAC) solder alloys are the most promising candidates to replace Sn–Pb solder alloys. However, their application is still facing several challenges; one example is the electrochemical corrosion behaviour, which imposes a risk to electronics reliability. Numerous investigations have been carried out to evaluate the corrosion performance of SAC lead-free alloys, regarding the effect of the corrosive environment, the different manufacturing technologies, the effect of fluxes, the metallic contents within the SAC alloys themselves, and the different alloying elements. In these studies, widely used electrochemical techniques are applied as accelerated corrosion tests, such as linear sweep voltammetry and electrochemical impedance spectroscopy. However, there is lack of studies that try to summarise the various corrosion results in terms of lead-free solder alloys including low-Ag and composite solders. This study aims to review these studies by showing the most important highlights regarding the corrosion processes and the possible future developments.

Local and post-buckling behavior of corroded axially-compressed steel columns

To investigate the effect of corrosion on the local and post-buckling behavior of axially-compressed steel members, H-shaped Q345B steel columns with different corrosion degrees were obtained by accelerated corrosion test. Then, an axial compression test was performed to analyze the relationships between the failure mode, local buckling load, and ultimate load and the corrosion degree. Finally, more than 80 finite element models of steel columns with different corrosion parameters were established in the software ABAQUS, and a modified direct strength method for corroded axially-compressed steel stub columns considering local buckling was proposed. The results showed that the axial-load capacity of the axially-compressed steel column decreased gradually with the increased degree of corrosion. The yield load, ultimate load and local buckling load of the most seriously corroded specimen decreased by 15.0%, 18.9% and 21.4%, respectively. The corrosion changed the failure modes of specimens and gradually decreased the half-wavelength, which weakened the plastic deformation capability of specimens and led to the failure mode of the steel columns transforming from strength failure to stability failure. In addition, the corrosion pits had less of an effect on the axial-load capacity of specimens than the thickness loss. Under the same corrosion type, the location and size of the corrosion would not affect the ultimate load of the axially-compressed members, which only depended on the damage degree of weakest section. Finally, the proposed formula can accurately predict the post-buckling behavior and ultimate load of corroded H-shaped axially-compressed steel columns by comparing the experimental data with the finite element results and the results in the existing literature.

Intergranular corrosion of AA6082 Al–Mg–Si alloy extrusion: The influence of trace Cu and grain boundary misorientation

In the present work, the influence of trace level Cu on intergranular corrosion (IGC) in AA6082 Al–Mg–Si alloy is studied using correlative accelerated corrosion testing and high resolution electron microscopy. Further, grain boundary structure and its correlation to IGC are also investigated using electron backscatter diffraction (EBSD) and transmission Kikuchi diffraction (TKD). It is found that in AA6082-T6 alloy with very low Cu content (0.06 wt%), about 13% of high angle grain boundaries have Al2Cu precipitates, which promotes IGC at the grain boundaries.