Metal ion release from electric guitar strings in artificial sweat

The aim of this study was to monitor the dissolution of metal ions from electric guitar strings. For characterization of investigated strings, two independent methods of analysis were chosen: ICP-OES and AAS. Electric guitar strings consisted of two separate parts: Sn-plated steel core wire which was hexagonal in cross section and Ni-plated steel wrap which was round in cross section. Dissolution of Ni²⁺, Mn²⁺, Si⁴⁺, Sn²⁺ and Fe³⁺ ions from electric guitar strings E6 and D4 were measured as a function of time in artificial sweat solution, at temperature of 37 °C according to the EN 1811:1999 standard test procedure. The determination of the amount of the metal ions released in the corrosive solutions was carried out by means of inductively coupled plasma-optical emission spectroscopy (ICP-OES). The mechanism of metal ions eluted in artificial sweat is discussed. The concentrations of dissolved metal ions in corrosive solution from E6 and D4 strings are decreasing in the following order: Fe³⁺ > Sn²⁺ > Mn²⁺ > Si⁴⁺ > Ni²⁺. Among all investigated metal ions, nickel is far the most allergenic. Since the amounts of the eluted Ni²⁺ did not exceed 0.5 μg cm⁻² week⁻¹, the investigated electric guitar strings should not induce contact dermatitis.     

Discovering key meteorological variables in atmospheric corrosion through an artificial neural network model

This paper presents a deterministic model for the damage function of carbon steel, expressed in μm of corrosion penetration as a function of cumulated values of environmental variables. Instead of the traditional linear model, we designed an Artificial Neural Network (ANN) to fit the data. The ANN numerical model shows good results regarding goodness of fit and residual distributions. It achieves a RMSE value of 0.8 μm and a R² of 0.9988 while the classical linear regression model produces 2.6 μm and 0.9805 respectively. Besides, F_LOF for the ANN model were next to the critical value.The improved accuracy provides a chance to identify the most relevant variables of the problem. The procedure was to add/remove one after the other the variables and perform from scratch the corresponding training of the ANN. After some trial and error as well as phenomenological arguments, we were able to show that some popular meteorological variables like mean relative humidity and mean temperature shown no relevance while the results were clearly improved by including the hours with RH < 40%. The results as such might be valid for a limited geographical region, but the procedure is completely general and applicable to other regions.     

Study of microstructure and corrosion kinetic of steel guitar strings in artificial sweat solution

Corrosion processes of strings on musical instruments occur frequently. Such processes significantly influence sound quality, but also human health because metals may provoke skin allergy. Therefore, in this study the corrosion process of six guitar strings and metal ions release associated with nickel allergy was monitored after immersion in sweat solution for 28 days. Dissolution of metal ions was measured as a function of time, and the changes of the samples after 28 days were studied by SEM/EDS. The results have shown that the amounts of dissolved metal ions in corrosive solution are decreasing in the following order: Fe³⁺ < Sn²⁺ < Mn²⁺ < Si⁴⁺ < Ni²⁺. The corrosion of electric guitar strings in artificial sweat solution was determined by the solubility of samples. The electric guitar strings E6, A5 and D4 corrosion kinetic in artificial sweat followed parabolic rate relation, while g3, h2 and e1 strings followed linear rate relation. After the 4 weeks of monitoring, the quantities of the nickel eluted ions did not exceed the limits prescribed by standard regulations. Therefore, such items do not present a threat to human health.     

Prediction of pitting corrosion of surface treated AISI 316L stainless steel by artificial neural network

Abstract

This paper presents an artificial neural network based solution method for modelling the pitting resistance of AISI 316L stainless steel in various surface treated forms. Surface treatment is a promising technique for improving the corrosion resistance of stainless steels. In this study, cyclic polarisation tests were performed before and after surface treatment. Experimental results were modelled by the neural network. The artificial neural network model exhibited superior performance based on the fitness of the observed versus predicted data. The results showed that the predicted data from the neural network model were considerably similar to the experimental data. The model has been saved and can easily be used to predict the corrosion in different surface treatment methods.     

Detection of corrosion steel under an organic coating by infrared photography

The application of an infrared camera for detecting corrosion under organic coatings was studied. The ruptured blistering area, blister and filiform corrosion can be monitored easily by infrared thermography. When the corroded specimen is heated, the temperature at the surface over the corroded area changed differently according to the type of corrosion.The extent of increase in temperature was in the following sequence: ruptured blister > filiform filament > intact part > blister.From the analysis of temperature distribution at the surface of specimen, the location, shape and size of the corroded area can be estimated.     

Prediction of corrosion behaviour of Alloy 22 using neural network as a data mining tool

Objective of this work was to develop an algorithm to predict behaviour of corrosion resistant metal alloys using a supervised neural network method as a data mining tool. We studied corrosion data on a nickel-based alloy, Alloy 22 which is of great industrial interest. This is an extension of a previously reported study on metallic glasses, carbon steel, and grade-2 titanium. The data mining results allow us to categorize and prioritize certain parameters (i.e. pH, temperature, time of exposure, electrolyte composition, metal composition, etc.) and help us understand the synergetic effects of the parameters and variables on corrosion behaviour.     

Localized corrosion of a 2219 aluminium alloy exposed to a 3.5% NaCl solution

This work is focused on the role of intermetallics in pitting corrosion of Al2219 alloy. Second phase particles were characterized by AES, SAM and EDX. Their behaviour in a solution of NaCl was investigated as a function of exposure time. The results confirmed the cathodic nature of the intermetallics with respect to the aluminium matrix. Corrosion products rich in aluminium and oxygen were found to progressively accumulate around the particles and iron was dissolved from the intermetallic, followed by back-deposition. Copper and manganese did not show any major activity. After 32 h of exposure the larger intermetallics were completely covered.     

Electrochemical corrosion behavior of a novel antibacterial stainless steel

A novel antibacterial stainless steel (ASS) with martenstic microstructure has been recently developed, by controlled copper ion implantation, as a new functional material having broad-spectrum antibacterial properties. The electrochemical corrosion behavior of the ASS in 0.05 mol/L NaCl was assessed using linear polarization and electrochemical impedance spectroscopy (EIS) and compared with that of a conventional stainless steel (SS) without copper ion implantation. The ASS exhibited higher corrosion susceptibility in the chloride medium; with a more negative (active) corrosion potential, higher anodic current density and lower charge transfer and polarization resistance. This has been attributed to the occurrence of copper-catalyzed interfacial reactions. A functional tool, 3-D presentation of EIS data, has been employed in analyzing the electrochemical corrosion processes as well as probing complex interfacial phenomena.     

The corrosion protection of mild steel by polypyrrole/polyphenol multilayer coating

Electrochemical synthesis of very thin polyphenol (PPhe) film was achieved on polypyrrole coated mild steel electrode (MS/PPy) and a multilayer coating was obtained, cyclic voltammetry technique was used for the synthesis. The corrosion performance of this multilayer coating and single PPy coating were investigated in 0.05 M H₂SO₄ solution by using electrochemical impedance spectroscopy (EIS), anodic polarization curves and open circuit potential (E_ocp)-time curves were used. It was found that the multilayer coating could provide much better protection than the single PPy coating for corrosion of MS for much longer periods and an efficiency of 98.3% was determined for this coating after 340 h exposure time in corrosive medium. It is proposed that the very thin PPhe film coated on top of PPy coating lowered the porosity and improved the barrier effect of the coating significantly.     

A method of probabilistic analysis for steel pipeline with correlated corrosion defects

A method of probabilistic analysis is presented to consider effect of correlation of corrosion defects on steel pipeline failure. Failure probability of pipeline with correlated corrosion defects is modeled and compared with results from conventional method. The results showed that assumption of independent corrosion defects will lead to conservative results. The calculated results are within Ditlevsen bimodal bounds. This indicates the validity and feasibility of the proposed method. The combined effect of both the model sensitivity of prediction to variables and the uncertainty of variables should be taken into account in sensitivity analysis.     

The effect of counter anions on corrosion resistance of steel covered by bi-layered polypyrrole film

The bi-layered polypyrrole (PPy) coatings were investigated for corrosion prevention of a carbon steel. The inner layer was doped with the Keggin structure anions of (PMo₁₂) and anions for stabilization of the passive oxide film at the metal-polymer interface, and the outer layer was doped with four organic anions of dihydroxynaphthalenedisulfonate (DHNDS), naphthalenedisulfonate (NDS), anthraquinonedisulfonate (AnqDS) or dodecylsulfate (DoS) for inhibition of the decomposition and release of PMo₁₂. The corrosion tests were performed in 3.5 wt.% NaCl aqueous solution. The corrosion resistance of the steels covered by the bi-layered PPy films was found in the following order: PPy-PMo₁₂/PPy-DHNDS < PPy-PMo₁₂/PPy-NDS < PPy-PMo₁₂/AnqDS < PPy-PMo₁₂/PPy-DoS. The performance of corrosion protection related to the oxidized state of the polymer was discussed.     

Corrosion and corrosion test methods of zinc coated steel sheets on automobiles

The effect of zinc and zinc alloy coated steel sheets on perforation corrosion in actual automobiles and the relevant accelerated corrosion test methods were studied. The main factor affecting corrosion in the crevice of lapped panels was the coating weights of zinc and zinc alloys rather than the type of coating. Perforation corrosion process of galvanized steel in the crevice of lapped portion in automobiles was divided in four stages. Based on the analysis of corrosion in actual automobiles, a Perforation Corrosion Index, PCI for lapped steel panels was proposed. Assuming PCI for various accelerated corrosion test methods, the corrosion resistance of various types of coated steel sheets in actual environments was evaluated.     

Anisotropic 3D growth of corrosion pits initiated at MnS inclusions for A537 steel during corrosion fatigue

The 3D growth behaviour of pits initiated at MnS inclusions for A537 steel under cyclic load condition has been investigated by confocal scanning laser microscope and finite element analysis. The results indicated the growth of pit for cyclic-stressed samples showed anisotropic behaviour. Significant higher growth rate was found in the direction perpendicular to load axis. Finite element analysis indicated that localized plastic strain played an important role on pit growth. The growth kinetics of pit in width direction is dominated by plastic deformation. Coalescences of pits further increase the growth rate of pit as predicted by finite element analysis.     

Understanding corrosion via corrosion product characterization: I. Case study of the role of Mg alloying in Zn-Mg coating on steel

In the present work the corrosion inhibitive role of Mg in Zn-Mg coatings is considered for different stages of corrosion. Corrosion product characterization was carried out using XRD, IRRAS, MEB-FEG-EDS on technical Zn-Mg coatings after various exposure times in a standardized cyclic corrosion test. The results are compared with artificial corrosion products obtained by chemical and electrochemical synthesis. The importance of the ageing and the role of the atmospheric CO₂ on the nature and morphology of the corrosion products are discussed. The corrosion resistance of Zn-Mg alloy is correlated with the stabilization of simonkolleite against its transformation into smithsonite, hydrozincite, and zincite during ageing cycles in presence of CO₂. The stabilization appears to be due to the preferential formation of magnesium carbonates. Thermodynamic modeling and titrometric analysis demonstrate that Mg²⁺ enhances simonkolleite during dry-wet cycling by (1) removing carbonate from the environment and thereby limiting of the transformation of simonkolleite into zincite, smithsonite, and hydrozincite and by (2) buffering the pH of the electrolyte around 10.2 due to the precipitation of Mg(OH)₂ preventing the dissolution of zinc based corrosion products into soluble hydroxide complexes.     

Improving the intergranular corrosion resistance of 304 stainless steel by grain boundary network control

The grain boundary network (GBN) was controlled by grain boundary engineering (GBE) in a 304 stainless steel. The total length proportion of Σ3ⁿ coincidence site lattice (CSL) boundaries was increased to more than 70% associating with the formation of large size highly twinned grain-cluster microstructure. Only coherent twin boundaries (Σ3_c) were found to be resistant to intergranular corrosion (IGC) and only such boundaries could be termed “special” ones. The improvement of resistance to IGC of the GBE specimen can be attributed to the large size grain-clusters associated with high proportion of the Σ3ⁿ boundaries and the interconnected Σ3ⁿ-type triple junctions.     

Effect of surface finishing of a Zr-based bulk metallic glass on its corrosion behaviour

Zr-based metallic glasses passivate spontaneously, but exhibit also a certain pitting susceptibility. On the example of the Zr₅₉Ti₃Cu₂₀Al₁₀Ni₈ alloy studied in 0.01 M Na₂SO₄ + x M NaCl (x = 0-0.1) electrolytes it is demonstrated that the surface finishing state and the pre-exposure conditions can significantly influence the free corrosion and anodic polarisation behaviour. Mechanical fine-polishing procedures can lead to extremely smooth topographies but also to Cu enrichment at the surface. This yields a pronounced Cu dissolution at low anodic polarisation prior to stable passivity and increases the pitting initiation susceptibility as compared to mechanically ground surface states.     

Electropolishing effects on corrosion behavior of 304 stainless steel in high temperature, hydrogenated water

The corrosion rate of electropolished 304 stainless steel surfaces (UNS S30400) is found to be lower by more than a factor of three relative to that determined previously for machined surfaces in mildly alkaline, hydrogenated water at 260 °C. This favorable result is attributed to significant changes in nanocrystallinity of the corrosion oxide layer caused by the removal of surface microstrain, which had been imparted during the machining process. In the absence of microstrain, a low-porosity, protective, corrosion layer forms that is composed of extremely small and uniformly-sized spinel oxide crystals. Application of scanning electron microscopy (FEG-SEM), X-ray diffraction and X-ray photoelectron spectroscopy (XPS) in conjunction with ion milling and target factor analyses, found the corrosion layer to consist of micrometer-size crystals of a ferrite-based spinel oxide (non-protective) over-laying nanometer-size crystals of a chromite-based spinel oxide (protective). Composition of both phases is unchanged from that previously observed on corroded, machined surfaces and is representative of solvus phases in the immiscible Fe(Fe_1−nCr_n)₂O₄ spinel binary. The smaller size (10 vs. 26 nm) and greater surface density (∼10,000 vs. 835 μm⁻²) of the chromite-based crystals relative to those formed on machined (i.e., cold-worked) surfaces, however, is consistent with the absence of preferred high energy nucleation sites on strain-free surfaces. Therefore, electropolishing, which removes surface microstrain induced by cold-working, represents a preferred reference surface condition.     

The behaviour of praseodymium 4-hydroxycinnamate as an inhibitor for carbon dioxide corrosion and oxygen corrosion of steel in NaCl solutions

Praseodymium 4-hydroxycinnamate (Pr(4OHCin)₃) was investigated as a novel corrosion inhibitor for steel in NaCl solutions, and found to be effective at inhibiting corrosion in both CO₂-containing and naturally-aerated systems. Surface analysis results suggest that the corrosion inhibition ability of Pr(4OHCin)₃ in the naturally-aerated corrosion system could be attributed to the formation of a continuous protective film. For the CO₂-containing system, the corrosion inhibition efficiency of Pr(4OHCin)₃ was predominantly because of formation of protective inhibiting deposits at the active electrochemical corrosion sites, in addition to a thinner surface film deposit.     

Evaluation of corrosion inhibition of brass-118 in artificial seawater by benzotriazole using Dynamic EIS

The paper presents the results of corrosion behaviour of brass-118 in artificial seawater and the inhibitor effect of benzotriazole (BTA) by using a novel method called dynamic electrochemical impedance spectroscopy (DEIS). This method allows the tracing of the dynamics of the corrosion and the inhibition process based on the evaluation of electrical parameters of the equivalent circuit. Instantaneous impedance spectra recorded up to 10 h show that an exposure of few hours is not enough for the determination of inhibition efficiency. The results indicate the usefulness of DEIS technique in the field of inhibitor research.     

Effect of Caand Mg on corrosion and scaling of galvanized steel pipe in simulated geothermal water

In this paper, the effects of scaling ions (Ca²⁺ and Mg²⁺) on corrosion and scaling processes of galvanized steel pipe in geothermal water are presented. Spherical corrosion products and needle-shaped scale coexisted on the pipe surface. The concentration of Zn²⁺ and OH⁻ affected the nuclei formation of scale. The corrosion products and scale were identified as Zn(OH)₂, ZnO, CaCO₃ and MgCO₃, respectively. When scale formed on the galvanized steel pipe, the corrosion rate slowed down and the pitting region became smaller.