The deterioration of metals under the influence of corrosion is a costly problem faced by many industries. Therefore, particlereinforced composite coatings are being developed in different technological fields with high demands for corrosion resistance. This work studies the effects of nanoplatelet reinforcement on the durability, corrosion resistance, and mechanical properties of copper-nickel coatings. A 90 : 10 Cu-Ni alloy was coelectrodeposited with nanoplatelets of montmorillonite (Mt) embedded into the metallic matrix from electrolytic baths containing 0.05, 0.10, and 0.15% Mt. X-ray diffraction of the coatings indicated no disruption of the crystal structure with addition of the nanoplatelets into the alloy. The mechanical properties of the coatings improved with a 17% increase in hardness and an 85% increase in shear adhesion strength with nanoplatelet incorporation. The measured polarization resistance increased from 11.77 kΩ⋅cm 2 for pure Cu-Ni to 33.28 kΩ⋅cm 2 for the Cu-Ni-0.15% Mt coating after soaking in a simulated seawater environment for 30 days. The incorporation of montmorillonite also stabilized the corrosion potential during the immersion study and increased resistance to corrosion.
Electrodeposition of different metals and alloys is popular for corrosion resistance because of the major problems that persist with corrosion. Two major alloys of Cu-Ni, 70-30 and 90-10, have been evaluated for corrosion protection on a stainless steel substrate. Copper and copper alloys are commonly used in marine environments to resist biofouling of materials by inhibiting microbial growth.The results show that the incorporated montmorillonite in the Cu-Ni matrix at 0.05% (238.1-297.5 kΩ cm 2 ) and 0.1% (138.2-102.9 kΩ cm 2 ) improved the overall corrosion resistance versus the pure alloy film (71.9-68.5 kΩ cm 2 ). These coatings hold promise for the off-shore drilling environment in the oil and gas industry.
This paper investigates the electrochemical behavior of p-aminophenol (PAP) on commercially available carbon screen-printed electrodes (CSPEs) and gold screen-printed electrodes (GSPEs) at neutral and basic pHs for the development of inexpensive immunoassays. The electrochemical oxidative signal from PAP results from its adsorption to the electrode. The formation of self-assembled monolayers on gold electrodes prevented PAP adsorption but also reduced its oxidative current, confirming that adsorption increases signal production. On bare electrodes, PAP adsorption results in oxidative current variability depending on the electroactive surface area of the screen-printed electrode. This variability could not be remedied by cleaning and reusing the same GSPE. Decreasing the PAP concentration to 3.8 μM greatly improved the consistency of the measurements, suggesting that the adsorption of PAP is concentration-dependent. Multiple PAP oxidations on the same electrode caused polymerization, limiting PAP in continuous monitoring applications. Infrared and Raman spectroscopy allow the distinction between adsorbed PAP and electropolymerized PAP on the surface of a gold wafer. The results from this study suggest that the use of PAP production in immunoassays with SPEs must be fine-tuned, and electrodes must be cleaned or disposed of between measurements.
Shewanella oneidensis is an electroactive bacterium that has the ability to harvest electrons from insoluble metals in its environment for biological processes via dissimilatory metal reduction (DMR). There are 4 mechanisms by which S. oneidensis accomplishes these reductions: direct contact of the outer cell membrane to the metals, protein “nanowires” that extend from the cell surface, metal chelators that solubilize the metals, and small molecule electron shuttles. While evidence suggests S. oneidensis predominately utilizes soluble electron shuttles for DMR, it has yet to be directly proven. If the exact mechanism or mechanisms could be elucidated, S. oneidensis could be employed in a fuel cell that rids polluted water of metal contaminants in the process of generating electricity.
For this research, scanning electrochemical microscopy (SECM) was used to investigate the DMR processes of S. oneidensis. By coupling SECM to an inverted microscope, we optically imaged the bacteria during two-dimensional electrochemical measurements. Combined with advances in carbon ultra-micro electrode fabrication, this optical-SECM was used for high resolution scans of S. oneidensis biofilms, as well as planktonic bacteria.
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