Electrochemical Corrosion Reaction Research Articles

Rapid Synthesis of AxWO3 (A = H, Na, K) Tungsten Bronze Materials with Strong Near‐Infrared Absorption and Enhanced Photoelectric Anticorrosion Properties

The intrinsic reduction method is extended for the synthesis of tungsten bronzes (TBs), and monoclinic phase hydrotungsten bronze (HWO), tetragonal phase sodium tungsten bronze (NaWO) and hexagonal phase potassium tungsten bronze (KWO) are obtained. The introduction of cations brought a large number of localized state free electrons, which endowed TBs with strong near‐infrared (NIR) absorption and achieved light energy utilization covering almost the entire solar spectrum in the form of localized surface plasmon resonance (LSPR) and small polariton transfer. The strong NIR absorption enhanced the corrosion protection performance of tungsten bronze coatings, especially the HWO coating, which had an increased impedance value of 859.5% compared to the pure epoxy resin. The excellent corrosion resistance of TBs inhibitors can be derived from the strong NIR absorption enhanced photocathodic protection and local magnetic field, which improved the charge transfer resistance of the coating by nearly two orders of magnitude and greatly inhibited the charge movement in the electrochemical corrosion reaction. This study discovered the contribution of oxygen vacancy‐enhanced NIR absorption to the electrochemical anticorrosion properties, expanding the application area of TBs and making an important contribution to innovative anticorrosion strategies.

Electrochemical behavior and anti-corrosion property of Ti3C2Tx MXene/LDH heterostructured coating on aluminum alloy

Two-dimensional (2D) materials show potential applications in anti-corrosion on metals in aggressive medium. However, it remains a challenge in uniform dispersion, complex functionalization, and structure control of 2D nanosheets in composite coatings. Herein, a Ti3C2Tx/layered double hydroxide (LDH) heterostructured coating for corrosion protection on Al alloy is proposed by in situ growth and dip coating process. Without complex functionalization, dispersion, and structure control, the heterostructured coating provides an enhanced corrosion resistance confirmed by electrochemical tests and microstructure characterization. As a result, the incorporation of Ti3C2Tx MXene can decrease the corrosion current density by ~40-fold and increase the coating resistance by 54-fold compared to bare Al alloy. Furthermore, the Ti3C2Tx/LDH coating still exhibits a self-healing ability after immersion in 3.5 wt% NaCl solution over 3 days, thereby providing long-term corrosion protection on Al alloy for 30 days. The protective behavior is attributed to the blocking effect and the feature of participating in electrochemical corrosion reaction and losing electrons of 2D MXene prior to the metal. This strategy provides a facile and effective approach to designing 2D materials-based anticorrosion coatings on Al alloy used in aggressive environments.

Graphene prepared by microfluidization process using induced parallel orientation strategy to enhance anti-corrosion of photocurable epoxy coatings

Graphene has excellent application prospects in anti-corrosion coatings because of its perfect impermeability. Unfortunately, graphene sheets rich in surface defects lead to a significant reduction in impermeability, and also tend to spontaneously aggregate and randomly arrange in the resin matrix to form conductive network, which exacerbates electrochemical corrosion reactions. Herein, a green, one-step method for preparing low-defect and few-layer modified graphene was proposed. Graphene was prepared and modified in one step from graphite by using calcein (CA) under microfluidization process to obtain CA noncovalent modified graphene (CAG) with 2–5 layers of sheets. CAG/epoxy (EP) coatings with high orientation were prepared by spinning and curing simultaneously. The coatings show excellent long-term anti-corrosion performance. After immersion for 55 days in 3.5 wt% NaCl solution, the impedance modulus of CAG0.5%/EP coating was about three orders of magnitude higher than that of EP coating. It is worth noting that when the CAG content increased to 1 %, the impedance value remained above 1.8 × 1011 Ω cm2. The excellent anti-corrosive properties of the composite coating can be attributed to the extremely high orientation of graphene, which prevents the formation of conductive pathways and maximizes the barrier effect of graphene. In parallel, the modified graphene reduces the agglomeration between the graphene sheet and imparts excellent interfacial bonding with the epoxy, thus avoiding the formation of micro-cracks in the coating.

Chemical mechanical polishing exploiting metal electrochemical corrosion of single-crystal SiC

A chemical mechanical polishing (CMP) method of single-crystal SiC is proposed based on metal electrochemical corrosion. The oxidation mechanism of SiC by electrochemical corrosion of metals and the mechanism of surface material removal are revealed by corrosion and polishing experiments. The metallic aluminum sheet that is in contact with single-crystal SiC was immersed in sodium sulfate (Na2SO4) electrolyte solution, and the morphological and elemental changes of single-crystal SiC surface were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Then, polishing experiments were conducted on single-crystal SiC using different metal polishing discs and different polishing solutions. The XPS and EDS results show that single-crystal SiC can electrochemically corrode to generate a silica reaction layer. The use of metal polishing discs in CMP significantly improved the material removal rate (MRR) of SiC, with the highest MRR of 1011.43 nm/h for aluminum polishing discs, followed by that for iron polishing discs, and the lowest MRR for copper and alumina ceramic polishing discs. When metal polishing discs were used, the addition of electrolyte solution significantly improved the MRR and reduced the surface roughness of the SiC surface. Polishing with Na2SO4 solution when the polishing disc was aluminum disc, the MRR was higher than that for using deionized water by 105%, and the surface roughness Ra decreased by 37.8% to 2.8 nm. The metal electrochemical corrosion reaction can promote the oxidation of single-crystal SiC and generate a soft SiO2 reaction layer on the SiC surface, thereby improving the polishing efficiency of single-crystal SiC.

Chemical Inductor.

A multitude of chemical, biological, and material systems present an inductive behavior that is not electromagnetic in origin. Here, it is termed a chemical inductor. We show that the structure of the chemical inductor consists of a two-dimensional system that couples a fast conduction mode and a slowing down element. Therefore, it is generally defined in dynamical terms rather than by a specific physicochemical mechanism. The chemical inductor produces many familiar features in electrochemical reactions, including catalytic, electrodeposition, and corrosion reactions in batteries and fuel cells, and in solid-state semiconductor devices such as solar cells, organic light-emitting diodes, and memristors. It generates the widespread phenomenon of negative capacitance, it causes negative spikes in voltage transient measurements, and it creates inverted hysteresis effects in current–voltage curves and cyclic voltammetry. Furthermore, it determines stability, bifurcations, and chaotic properties associated to self-sustained oscillations in biological neurons and electrochemical systems. As these properties emerge in different types of measurement techniques such as impedance spectroscopy and time-transient decays, the chemical inductor becomes a useful framework for the interpretation of the electrical, optoelectronic, and electrochemical responses in a wide variety of systems. In the paper, we describe the general dynamical structure of the chemical inductor and we comment on a broad range of examples from different research areas.

Experimental and DFT studies on corrosion protection performance of epoxy/graphene quantum dots@TiO2 nanotubes coatings

In this paper, the nanohybrids of graphene quantum dots and TiO2 nanotubes (GQD@TNT) with different GQD:TNT weight ratios of 1:0.5, 1:1, and 1:2 are synthesized which are abbreviated as H (1:0.5), H (1:1), and H (1:2), respectively, and further modified with 3-(aminopropyl) triethoxysilane. Then, the silane-modified nanohybrids are loaded at 0.3 wt% in the solvent-borne epoxy matrix to achieve anti-corrosion nanocomposite coatings on the steel substrates. The results reveal that the coatings loaded with silane-modified H (1:1) more effectively enhance the corrosion protection efficiency of the polymer coatings, which has a low-frequency impedance modulus of 5.64 × 109 Ω·cm2 even after 90 days of immersion in the 3.5 wt% NaCl solution. Moreover, the density functional theory (DFT) method is performed to explore the energetics and the interaction mechanisms at each interface. The results imply that the strong adhesions observed at each interface would twist and increase the diffusion path of the corrosive agents, and consequently, retard the electrochemical corrosion reactions at the surface of the metal. Therefore, the proposed strategies could be successfully applied for the development of long-term anti-corrosion coatings.

Analysis of pit and its effect on electrochemical corrosion reaction in oil and gas pipelines

A parametric pit design in the outer surface of the oil pipeline buried under the soil atmosphere is investigated. This study analyzes the effect of pit size and corrosion contours to evaluate the metal degradation due to various characteristics that impact the corrosion on the oil pipeline. A 3D design of the model has been chosen, and its geometry is modeled in COMSOL MULTIPHYSICS, and appropriate meshing is done before computing to analyze impact of pit size and electron current density in oil pipeline. The behaviour of the pit design was then analysed using various parameters such as electron current density, corrosion rate, the impact of the pit size in localized area. The current findings in the study shows that risk of metal degradation and the depth of the pit size gives a relationship for corrosion in the localized area and the risk for pitting corrosion can be reduced by improving pipeline condition monitoring.

CO2 corrosion behavior of high-strength martensitic steel for marine riser exposed to CO2-saturated salt solution

CO2 corrosion is an inevitable problem of marine riser steel for oil and gas transportation. In the following work, the corrosion behavior was revealed in terms of microstructure characterization, corrosion kinetic curves, morphology and phase composition analysis of corrosion products, distribution characteristics of elements in corrosion products and electrochemical corrosion behavior. The results showed that FeCO3 crystals gradually evolved from dispersed clusters to complete FeCO3 layers with the extension of exposure time, which improved the protection ability of the corrosion product layer to the substrate. With the prolongation of corrosion time, the protective effect of the corrosion product layer on the substrate was gradually enhanced. The self-corrosion potential moved to the positive direction and the self-corrosion current density decreased. As a result, the corrosion rate gradually decreased and tended to be stable. The increase of corrosion-resistant elements content made the self-corrosion current density significantly decreased. The high content of corrosion-resistant elements effectively hindered the contact of corrosive ions with the substrate and inhibited the electrochemical corrosion reaction.

Unusual hydrogen explosions due to unanticipated metal‐water reactions

AbstractInadvertent generation of hydrogen from ambient temperature metal‐water chemical and electrochemical reactions have been responsible for a surprising number of hydrogen explosions. This paper describes three sets of incidents involving different metals in applications that are normally considered free of explosion hazards. The first set of incidents involves wet alkaline incinerator ash with an aluminum content of at least 2%. The second set of incidents involves copper conductor electrochemical reactions in subsea electrical cable. The third set involves electrochemical corrosion reactions in galvanized dry sprinkler pipe. In all three applications, test data are discussed to elucidate the specific reactions and potential preventive and mitigation measures.

Investigation of in-situ polymerization synthesized carbon-coated zinc oxide as anode material for Zn/Ni secondary battery

Using the resorcinol-formaldehyde (RF) resin as carbon source, core-shell structured carbon-coated zinc oxide (ZnO@RFC) was synthesized by cetyltrimethylammonium bromide (CTAB) assisted in-situ polymerization followed with carbonization process. The results showed that the ZnO particles were uniformly coated by an amorphous carbon layer. The excellent structural stability and high electrochemical performance depend it to be designed into carbon shell with a tunable thickness up to 14.4 nm, resulting in the ZnO@RFC anode delivers initial discharge specific capacity of 543 mAh g−1 and optimized 125 cycle life with capacity retention of 97.5% for Zn/Ni secondary batteries. And the effects of the thickness of carbon shell on electrochemical performance, corrosion and hydrogen evolution reaction are fully investigated. The results indicate that the carbon shell not only improves the electrical conductivity between ZnO particles but also increases the stability of ZnO in electrolyte.

Understanding the Mechanisms of Early Stage Aluminum Corrosion

Aluminum alloys are widely used in many applications due to their inherent corrosion resistance, which is attributed to the formation of a protective oxide layer. However, the strength and durability of many Al-based materials is reduced in humid environments. Consequently, detailed mechanistic understanding of corrosion reactions over time is necessary to predict the cost, safety, and performance. Most of the current knowledge of atmospheric aluminum corrosion is built on response relationships upon extensive corrosion and typically involve a first-order correlation of corrosion data with environmental conditions. However, mechanistic understanding of corrosion processes is still limited, particularly at the early stages of exposure to humid environments. In addition, the effects of electrolytes such as sodium chloride present in the environment are still not fully understood. This presentation will focus on our recent efforts to reveal the mechanistic dependence of electrochemical aluminum corrosion in humid air in the presence of NaCl. The rate of corrosion is explored through complimentary experimental and theoretical analyses relating corrosion rate to electrolyte chemistry, mass uptake and corrosion products. As an experimental platform, we use quartz crystal microbalance (QCM) electrodes coated with aluminum and sodium chloride using sputtering techniques. Structure, composition, and surface morphology of the samples were characterized by grazing-incidence X-ray diffraction, FTIR spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy. The QCM provides operando data with nanogram resolution on the formation of the corrosion product layer, from which we can derive rate constants for aluminum surface reactions. We find that the reaction rate in dry air is negligible, but a dramatic acceleration is observed at 50% RH and above. In addition, this study provides additional insight into: 1) the influence of the sodium chloride film thickness on the rate and reaction products; 2) the role of surface termination and roughness on aluminum oxide/hydroxide formation; and 3) the electrochemical corrosion reaction rate acceleration as a function of temperature. Finally, based on the interplay between theory and experiment we achieved preliminary understanding of the rate-limiting steps, which we will use to develop validated computational models of early-stage (hours to several days) aluminum corrosion. Figure 1

The COVID-19 Pandemic, Part 1: Can Antimicrobial Copper-Based Alloys Help Suppress Infectious Transmission of Viruses Originating from Human Contact with High-Touch Surfaces?

The COVID-19 Pandemic, Part 1: Can Antimicrobial Copper-Based Alloys Help Suppress Infectious Transmission of Viruses Originating from Human Contact with High-Touch Surfaces?

Erosion Corrosion Behavior of Aluminum in Flowing Deionized Water at Various Temperatures.

To optimize the operating temperature and flow velocity of cooling water in a high voltage direct current (HVDC) thyristor valve cooling system, the erosion corrosion characteristics of aluminum electrodes in deionized water at various temperatures were studied. With increasing water temperature, the corrosion current of the aluminum electrode gradually increases and the charge transfer impedance gradually decreases, thus, the corrosion of aluminum tends to become serious. The aluminum electrode in 50 °C deionized water has the most negative corrosion potential (−0.930 V), the maximum corrosion current (1.115 × 10−6 A cm−2) and the minimum charge transfer impedance (8.828 × 10−6 Ω), thus, the aluminum corrosion at this temperature is the most serious. When the temperature of deionized water increases, the thermodynamic activity of the ions and dissolved oxygen in the deionized water increases, and the mass transfer process accelerates. Therefore, the electrochemical corrosion reaction of the aluminum surface will be accelerated. The corrosion products covering the aluminum electrode surface are mainly Al(OH)3. With increasing water temperature, the number of pits and grooves formed by corrosion on the aluminum surface increased. In this paper, the molar activation energy Ea and the equilibrium constant K of the aluminum corrosion reaction with various temperatures are calculated. This clarifies the effect of temperature on the aluminum corrosion reaction, which provides a basis for protecting aluminum from corrosion. The results of this study will contribute to research that is focused on the improvement of production techniques used for HVDC thyristor valve cooling systems.

Role of hydroxyl group in cerium hydroxycinnamate on corrosion inhibition of mild steel in 0.6 M NaCl solution

The corrosion inhibition mechanism of cerium hydroxycinnamate compounds has been studied and compared as an effective corrosion inhibitor for steel in an aqueous 0.6 M NaCl solution. Surface analysis results showed that the surface of steel coupons exposed to solutions containing cerium hydroxycinnamate compounds has less signs of corrosion attack due to a formation of the protective film, while the surface of mild steel coupons exposed to 0.6 M chloride solution without inhibitor additions was severely corroded due to pitting. Electrochemical results performed a good inhibition performance and information of the formed protective deposit that hinders the electrochemical corrosion reactions with a dominance of anodic inhibition mechanism. The results also indicated that the addition of cerium hydroxycinnamate compounds to 0.6 M NaCl solution could mitigate electrochemical corrosion reactions, reduce protective and double layer CPE magnitudes, and improve protective and charge transfer resistances. Furthermore, cerium 2-hydroxycinnamate showed better efficient corrosion inhibitor in comparison with cerium 4-hydroxycinnamate for steel in aqueous media containing 0.6 M chloride ion.

AN INVESTIGATION OF AGANOERION POLYMORPHUM LEAF EXTRACT AS A COPPER WORKING FLUIDS’ ADDITIVE

This work presents the Aganonerion Polymorphum leaf extract as an additive for metals working fluids (MWF). The results indicated that the Aganonerion Polymorphum leaf extract additive shows high corrosion resistance and very small changes of the MWF composition as well as its properties. These benefits are attributed to the forming protective inhibiting deposits on the copper surface that control the electrochemical corrosion reactions. In addition, the study also compared the Aganonerion Polymorphum leaf extract with a commercial inhibitor, imidazolines, in investigated solution at the same experimental conditions.

A review of elemental sulfur deposition in high sulfur-content natural gas transmission pipeline

High sulfur-content natural gas includes hydrogen sulfide, mercaptans, sulfoethers, and other sulfurous substances, with the major component being hydrogen sulfide. The development of high sulfur-content natural gas fields worldwide ensures the supply of not only clean energy, but also raw materials for industrial sulfur products. However, supersaturated precipitation of gaseous sulfur yields solid sulfur particles by nucleation, coagulation, and agglomeration with changing operation pressure, temperature, and species and concentration of gas components in high sulfur-content natural gas transmission pipelines. The solid particles will flow with the natural gas, and when the dynamic conditions for particle deposition are fulfilled, they will be deposited in pipeline. The deposition of solid sulfur particles will cause blockages in the transmission pipeline; furthermore, the elemental sulfur contacting the metal surface of the pipeline will cause electrochemical and chemical corrosion reactions. Eventually, the consequences of sulfur deposition in high sulfur-content natural gas transmission pipelines will cause serious hazards for pipeline operation and production. This paper summarizes the advances in the calculation of the sulfur gas-solid phase equilibrium, understanding of the growth and ablation kinetics mechanism of solid sulfur particles, and development of a gas-solid two-phase flow mathematical model. To fulfill the need for theory and experimental methods for predicting and preventing sulfur deposition in high sulfur-content natural gas transmission pipelines, the following three topics should be emphasized in future studies: First, limited experimental data is available on elemental sulfur solubility in sour gas at the pressure and temperature conditions of transmission pipelines, so sulfur solubility measurements should be established in the pressure and temperature range ( P ≤15.0 MPa, T ≤333.15 K) of transmission pipelines, considering the very low sulfur solubility under these conditions. Second, mathematical models of solid sulfur particle growth kinetics should be established based on molecular dynamics (MD) simulations with statistical mechanics and thermodynamics, combined with crystallization kinetics theory to determine nucleation, growth, and ablation behavior under the conditions of natural gas transmission pipelines. Third, mathematical models of the gas-solid two-phase flow in the transmission pipelines should be built considering the gas-solid phase change of elemental sulfur, and the growth and ablation of sulfur particles these models should involve the coupling effects of multiple parameters such as pipeline pressure, temperature, gas composition, and flow rate. These models could provide a quantitative description of elemental sulfur precipitation, sulfur particle growth, and particle flow behavior in high sulfur-content natural gas. Accordingly, the exact quantity and position of elemental sulfur deposition in high sulfur-content natural gas transmission pipelines can be predicted. These achievements will contribute to sulfur deposition prevention and improvement of control technology, as well as provide technical support for the design and management of high-sulfur natural gas transmission pipelines.

Comparative study of the testing approaches for the susceptibility of high-strength fasteners to environmental hydrogen embrittlement (EHE)

Abstract Low-alloyed, high-strength steels with yield strength above 1200 MPa are frequently used in the automotive industry, in order to reduce the weight of the components. However, hydrogen embrittlement susceptibility is often a concern for this group of materials. Hydrogen can be produced on the metal surface, as a result of electrochemical corrosion reaction during service. The aim of this study is to evaluate the impact of the various loading procedures according to the existing technical specifications for environmental hydrogen embrittlement (EHE) testing. The hydrogen embrittlement susceptibility of high strength fasteners (strength class 14.8) was tested according to the well-established testing specifications: DIN 50969-2, DIN EN ISO 7539, ASTM F1624-12 in 5 wt.-% sodium chloride solution acidified to pH 3 with hydrochloric acid. Open circuit potential measurements were carried out during the testing procedure to gain understanding of the damage process in each of the testing approaches. Under the chosen testing conditions, rising step load (RSL) testing approach, specified in ASTM F1624-12, appeared as the most sensitive method for the evaluation of the material's hydrogen embrittlement susceptibility.

Adaptive Polymeric Coatings with Self‐Reporting and Self‐Healing Dual Functions from Porous Core–Shell Nanostructures

AbstractIn biological system, early detection and treatment at the same moment is highly required. For synthetic materials, it is demanding to develop materials that possess self‐reporting of early damage and self‐healing simultaneously. This dual function is achieved in this work by introducing an intelligent pH‐responsive coatings based on poly(divinylbenzene)‐graft‐poly(divinylbenzene‐co‐methacrylic acid) (PDVB‐graft‐P(DVB‐co‐AA)) core–shell microspheres as smart components of the polymer coatings for corrosion protection. The key component, synthesized PDVB‐graft‐P(DVB‐co‐AA) core–shell microspheres are porous and pH responsive. The porosity allows for encapsulation of the corrosion inhibitor of benzotriazole and the fluorescent probe, coumarin. Both loading capacities can be up to about 15 wt%. The polymeric coatings doped with the synthesized microspheres can adapt immediately to the varied variation in pH value from the electrochemical corrosion reaction and release active molecules on demand onto the damaged cracks of the coatings on metal surfaces. It leads simultaneously to the dual functions of self‐healing and self‐reporting. The corrosion area can be self‐reported in 6 h, while the substrate can be protected at least for 1 month in 3.5 wt% NaCl solution. These pH‐responsive materials with self‐reporting and self‐healing dual functions are highly expected to have a bright future due to their smart, long‐lasting, recyclable, and multifunctional properties.

Influence Factors of the Generation and Accumulation of Electric Charge on the Oil-Delivery Metal Pipelines

The interfacial electrification properties play an important role in the electrochemical corrosion reaction which leads the electrostatic charge to generate and accumulate on the metal surface when the insulating oil flows through a metal pipe. In this paper, the interfacial electrification properties resulted by the oil flow rate and the action of electric charge trapper are investigated by measuring the current and potential on the surface of the test metal pipe. The measured results showed that the current and potential between the metal pipe and the earth increased with the rise of flow rate; and as the flow rate increased, the growth trends of the current and potential difference between two close flow rates increased and decreased, respectively, while there was an electric charge trapper set in the radial direction of the pipe, the measured current and potential decreased compared with that of without electric charge trapper, which was because it captured and caught part of charge in the oil flow bulk to neutralize the opposite charge on the surface of the metal pipe.

Copper precipitation as consequence of steel corrosion in a flow-through experiment mimicking a geothermal production well

Decreasing production rates and massive precipitation of native copper (Cu(0)) were observed in the production well at the geothermal research facility Groß Schönebeck (Germany). The Cu precipitates filling up the well are a product of an electrochemical corrosion reaction between dissolved copper (Cu2+, Cu+) in the brine and iron (Fe(0)) of the carbon steel liner. It was hypothesized that this reaction occurs not only within the borehole, but also on the outside of the casing at contact between casing and reservoir rock as well as in the pores of the reservoir rock. To verify the assumption of potential clogging of the rock pores as well as to quantify the reaction and to determine reaction kinetics, a flow-through experiment was designed mimicking the reaction at depth of the well between sandstone samples (24 cm3 Fontainebleau), steel (carbon steel or stainless steel), and artificial formation water containing 1 mM Cu2+ at oxic or anoxic (O2 < 0.2 mg/L) conditions in dependence of temperature and salinity. Obtained experimental data served as input for a numerical reaction model to deepen the process understanding and that ultimately should be used to predict processes in the geothermal reservoir. Results showed that (1) with increasing temperature, the reaction rate of the electrochemical reaction increased. (2) High amounts of sodium and calcium chloride (NaCl + CaCl2) in the solution decreased the overall reaction inasmuch more Fe and less Cu was measured in the salt-poor solutions over time. (3) Strongest oxidation was observed in oxic experiments when not only native copper but also iron hydroxides were identified after the experiments in the pore space of the rock samples. (4) No reaction products were observed when stainless steel was used instead of carbon steel to react with the Cu2+ solution. A numerical flow-through reactor model was developed for PHREEQC based on the assumption that Fe(0) corrosion is kinetically controlled and subsequent Cu(0) precipitation occurs in thermodynamic equilibrium within the investigated experimental set-up. Calculated coefficients of determination comparing measured and simulated reaction rates for Fe and Cu underline the validity of the approach.