Redução electroquímica de iões de terras raras e o seu efeito na corrosão de metais

RESUMO: Os iões de terras raras estão entre os inibidores de corrosão de nova geração mais promissores. No entanto, foram encontradas condições onde a corrosão é acelerada na presença destes iões [1]. O caso mais relevante devido à sua importância é o aumento da corrosão do zinco no par galvânico zinco-ferro. Esse aumento está associado a uma reacção catódica adicional inesperada que é observada nas curvas de polarização obtidas experimentalmente. Esta nova redução corresponde a corrente catódica adicional que aumenta a oxidação do ânodo do par galvânico. Nesta comunicação analisa-se o impacto prático desta aceleração no par Zn-Fe e no aço galvanizado e procura-se identificar a natureza da nova reacção catódica.info:eu-repo/semantics/publishedVersio

Active self-healing coating for galvanically coupled multi-material assemblies

A new \"self-healing\" coating concept for active corrosion protection on galvanically coupled multi-material structures is reported in the present work. The novel approach is based on the combination of two types of nanocontainers with two different inhibitors in the same coating system. The nanocontainers confer a triggered release of both inhibitors which act in a synergistic way when an aluminum alloy is galvanically coupled with carbon fiber reinforced plastic. The layered double hydroxide and bentonite were used as functional nanocarriers for 1,2,3-benzotriazole and Ce3+ inhibitors respectively. Scanning vibrating electrode technique has been applied for the monitoring of galvanic corrosion activities and kinetics of self-healing processes in confined defects. The effective inhibition of electrochemical activity in the defects on coated galvanically coupled aluminum alloy with carbon fiber reinforced plastic was demonstrated for the first time. (C) 2014 Elsevier B.V. All rights reserved

Atomic layer deposition of nanometric alumina for corrosion protection of heterogeneous metallic surfaces: the case of aeronautical grade aluminium alloy 2024-T3

Nanometric layers of Al2O3 were applied by atomic layer deposition (ALD) on 2024-T3 aluminium alloy. The ALD layers suppressed the corrosion of the alloy as confirmed by Scanning Kelvin Probe Force Microscopy (SKPFM), polarization curves and Electrochemical Impedance Spectroscopy (EIS). The protection provided by the ALD layers weakened with the time of immersion and this was attributed to the incorporation of hydroxyl species in the film during the deposition at low temperature (100 ◦C) making them vulnerable to water.publishe

Protection of 2024-T3 aluminium alloy by corrosion resistant phytic acid conversion coating

The corrosion protection properties of environmentally friendly phytic acid conversion coatings were studied on 2024-T3 aluminium alloy. The films were prepared under acidic conditions with various pH values and characterised by SEM, EDS, ATR-FTIR and electrochemical techniques. The results indicate that the conversion coatings obtained by immersing the alloy in phytic acid solutions at pH from 3 to 5.5 provide excellent corrosion resistance. ATR-FTIR confirms that the film is formed by deposition of reaction products between Al3+ and phosphate groups in phytic acid molecules. The conformation models of the deposition film are proposed. (C) 2013 Elsevier B.V. All rights reserved

High-density antimicrobial peptide coating with broad activity and low cytotoxicity against human cells

Medical device-associated infections are a multi-billion dollar burden for the worldwide healthcare systems. The modification of medical devices with non-leaching coatings capable of killing microorganisms on contact is one of the strategies being investigated to prevent microorganism colonization. Here we developed a robust antimicrobial coating based on the chemical immobilization of the antimicrobial peptide (AMP), cecropin-melittin (CM), on gold nanoparticles coated surfaces. The concentration of AMP immobilized (110 mu g/cm(2)) was higher than most of the studies reported so far (<10 mu g/cm(2)). This translated onto a coating with high antimicrobial activity against Gram positive and negative bacteria sp., as well as multi-drug resistant bacteria. Studies with E. coli reporter bacteria showed that these coatings induced the permeability of the outer membrane of bacteria in less than 5 min and the inner membrane in approximately 20 min. Importantly, the antimicrobial properties of the coating are maintained in the presence of 20% (v/v) human serum, and have low probability to induce bacteria resistance. We further show that coatings have low toxicity against human endothelial and fibroblast cells and is hemocompatible since it does not induce platelet and complement activation. The antimicrobial coating described here may be promising to prevent medical device-associated infections. Statement of Significance In recent years, antimicrobial peptides (AMPs) have been chemically immobilized on surfaces of medical devices to render them with antimicrobial properties. Surfaces having immobilized cationic peptides are susceptible to be adsorbed by plasma proteins with the subsequent loss of antimicrobial activity. Furthermore, with the exception of very few studies that have determined the cytotoxicity of surfaces in mammalian cells, the effect of the immobilized AMP on human cells is relatively unknown. Here we report a coating based on cecropin-melittin peptide (CM) that maintains its antimicrobial activity against Gram-positive and negative bacteria including multi-drugs resistance bacteria in the presence of serum and has relatively low cytotoxicity against human cells. The reported coatings may be translated on to variety of substrates (glass and titanium) and medical devices to prevent device-associated microbial infection. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved