High throughput electrochemically driven metal microprinting with multicapillary droplet cell

A high speed and low-cost electrochemical additive manufacturing method for parallel microprinting of metals is proposed. Multicapillary 3D printed solution flow type microdroplet cells (Sf-MDC) with large capillary diameters (600 mu m) are used to electrodeposit high-quality Ni microstructures. Three Ni lines each having a width of around 900 mu m and a thickness of around 24.6 mu m, 20.7 mu m and 15.2 mu m are simultaneously printed on Cu substrate. The influence of temperature and scanning speed on the height of printed Ni lines is studied. Independent control of solutions inside each capillary enables the simultaneous formation of Ni-Cu-Ni and Cu-Ni-Cu microdots without any cross-mixing of solutions. By replacing 3D printed inner capillaries (around 600 mu m in diameter) with silica capillaries (around 100 mu m in diameter) inside the Sf-MDC, free standing 3D structures such as Ni microrods are successfully fabricated. Localized electrodeposition using the Sf-MDC allows parallel process 3D printing of metal microstructures for a wide range of applications

Effects of metal cations on corrosion of mild steel in model fresh water

The effects of metal cations on corrosion of mild steel in model fresh water were investigated by electrochemical techniques and immersion tests. Analysis of X-ray photoelectron spectroscopy showed that metal cations have large hardness of cations, X, are incorporated in passive films. The electrochemical and immersion results showed that Xis not suitable as a corrosion indicator of mild steel. A novel corrosion indicator, "corrosion inhibitory effect of cations Y '', that consists of X and molar volume ratio, Delta V, is proposed, and it is shown that the novel indicator can estimate the corrosion rate of mild steel in fresh water. (C) 2016 Elsevier Ltd. All rights reserved

Electrochemical Random Signal Analysis during Galvanic Corrosion of Anodized Aluminum Alloy

A new type of electrochemical random signal analysis technique was applied to galvanic corrosion of anodic oxide films formed on 6061-T6 aluminum alloy in NaCl containing 0.5 kmol⁄m3 H3BO4 ⁄ 0.05 kmol⁄m3 Na2B4O7 solutions. The effect of the anodic oxide film structure on the galvanic corrosion resistance was also examined. During incubation (before localized corrosion started), both current and potential change slightly from the initial value. The incubation period of porous type anodic oxide specimens is longer than that of barrier type anodic oxide specimens. During localized corrosion, the current and potential changing with fluctuations, and the potential and the current fluctuations show good correlation. The slope of the PSD of both potential spectra of anodized specimens is about minus one ( -1 ), after the localized corrosion has started. This technique allows observation of electrochemical impedance changes during localized corrosion

Corrosion inhibition of mild steel by metal cations in high pH simulated fresh water at different temperatures

Corrosion inhibition effect of metal cations on mild steel was investigated by immersion tests and electrochemical impedance spectroscopy in simulated fresh water with high pH at different temperatures. Immersion tests showed the different corrosion rates in the different solutions, and the Zn2+ containing solution showed the minimum corrosion rate at the experimental temperatures. The specimen immersed in the Zn2+ containing solution showed comparatively smooth surface which was observed by scanning electron microscopy and atomic force microscopy. EIS and XPS results suggested that Zn2+ attached to the steel surface and formed a layer, thereby improving the corrosion inhibition ability of steel

Analysis of the Initial Stage of Localized Corrosion on Zn and Zn Alloy Coated Steels by Photon Rupture Method

A photon rupture method, film removal by a focused pulse of pulsed Nd-YAG laser beam irradiation, has been developed as it enables oxide film stripping at extremely high rates without contamination from the film removal tools. In the present study, Zn and Zn-5mass%Al alloy coated steel specimens covered with protective nitrocellulose film were irradiated with a focused pulse of a pulsed Nd-YAG laser beam at a constant potential in 0.5 kmol m-3 H3BO3-0.05 kmol m-3 Na2B4O7 (pH=7.4) with/without 0.05 kmol m-3 of chloride ions to investigate the initial stage of localized corrosion. At low potentials, both samples reformed oxide film after the nitrocellulose films were removed by this method. The oxide film formation kinetics of Zn-55mass%Al follow an inverse logarithmic law, in agreement with Cabrera-Mott theory. However, at high potentials, localized corrosion producing corrosion products occured at the area where nitrocellulose film was removed. The dissolution current of the Zn coated steel samples is higher than that of Zn-5mass%Al coated samples at the same applied potential

Effects of solution composition on corrosion behavior of 13 mass% Cr martensitic stainless steel in simulated oil and gas environments

The effects of CH3COONa and CO2 on the corrosion behavior of 13 mass% Cr martensitic stainless steel in simulated oil and gas environments were investigated with electrochemical and surface analysis techniques. The electrochemical results showed that a plateau region and sudden increase in the current density of the anodic polarization curves. The current density of the plateau region decreased with increasing CH3COONa concentrations. The pitting corrosion potential shifted to the positive direction with increasing CH3COONa concentrations, and shifted to a negative value by adding CO2. From the surface analysis, a Cr enriched layer had formed on the sample surface after immersion tests, and the thickness of this layer became thinner with increasing CH3COONa concentration. The surface analysis results after the immersion tests suggested the presence of CH3COO- or HCO3- on the surface

Initial stage of localized corrosion in artificial pits formed with photon rupture on Zn-5 mass% Al alloy-coated steel

The photon rupture method, by which oxide film and metal are removed by focused pulsed Nd–YAG laser beam irradiation, was applied to form artificial micro-pits in Zn–5 mass% Al alloy-coated steel. The zinc alloy-coated layer was removed by pulsed laser irradiation treatment for about one second in a neutral buffer solution with NaCl. The rest potential transient with the laser treatment was measured. In the early stage of the laser treatment the rest potential of zinc alloy-coated steel changed to the negative direction immediately after every irradiation of a laser pulse and then returned to the previous value. However, after the steel substrate was exposed to the solution, the rest potential moved to the positive direction immediately after every irradiation of a laser pulse and then returned to the previous value. The amplitude and duration of the potential change after the laser irradiation increased with repetition of laser irradiation, related to the pit depth and the exposed area ratio of coated layer/steel substrate. The rest potential fluctuation difference can be explained by galvanic reaction change in the artificial pit formed by laser irradiation on the Zn alloy-coated steel

Initial Stage of Localized Corrosion in Artificial Pits Formed with Photon Rupture on 55mass%Al–Zn Coated Steels

The photon rupture method, whose oxide film and metal are removed by focused pulsed Nd–YAG laser beam irradiation was applied to form artificial micro pits in 55 mass% aluminum–zinc coated steels. The 15 μm coated layer was removed by 2 s of continuous laser irradiation in this experiment. The rest potential transients were measured during the laser irradiation. While the coated layer covered the steel substrate, the rest potential change in the negative direction just after the starts of the laser irradiation and then returned to the previous value. However, after the steel substrate was exposed to solution, the rest potential moved in the positive direction immediately after the discontinuation of the laser irradiation and then also returned to the previous value. The amplitude and duration of the potential changes after the laser irradiation increased with longer irradiation, related to the pit depth and exposed area ratio of coated layer/steel substrate. These rest potential fluctuation differences can be explained by galvanic reaction changes in the artificial pit formed on the coated steel during irradiation

Formation of oxide films for high-capacitance aluminum electrolytic capacitor by liquid-phase deposition and anodizing

Liquid phase deposition (LPD) treatment and anodizing were used to form oxide layer for a high-capacitance aluminum electrolytic capacitor. Formation of protective oxide layers and modification of LPD conditions make it possible to prolong the LPD duration and lead to the formation of TiO2 and NaF deposits on aluminum. A titanium oxide / aluminum oxide mixed layer was formed by a combination process of LPD treatment and anodizing. The capacitance of the formed layer was about 300% higher than that of an anodic oxide film formed on electropolished aluminum. The structures and compositions of the films that were formed were determined by transmission electron microscopy, scanning electron microscopy, and Rutherford backscattering spectroscopy