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.

Amorphous cerium molybdate nanowires (CMN) have been used to impart active corrosion protective properties to hybrid sol-gel coatings on AA2024. Inhibitive ability of the novel sal-gel coatings against corrosion has been studied in detail by electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). Localized electrochemical measurements demonstrate significant suppression of corrosion activity in micro-scale defects made in sal-gel coatings loaded with CMN when compared to blank systems. The mechanism of active protection involves release of cerium and molybdate ions from the sal-gel coating during immersion in NaCl electrolyte and their inhibiting action in corroding defects. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.

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.

The mechanisms of the initial stages of localized corrosion at cut edges were investigated for adhesively bonded Zn (Z) and Zn-Al-Mg (ZM) galvanized steel. The results provided strong evidence for the localized nature of corrosion of galvanized coatings at the cut edges and at the adhesive/zinc interface. In both cases a defined localized corrosion attack on zinc in Z sample was observed. On the contrary, in the case of the ZM specimen both zinc solid solution and eutectics exhibited local corrosion. The local attack at the adhesive/Z(ZM) interface was correlated with an anodic undermining process. It develops near the cut-edge surface and at the buried deep adhesive-zinc interface and results in adhesive disbonding in the buried interface. The electrochemical studies revealed that the corrosion kinetics at the metal cut-edges decreases during immersion, which could be due to formation of corrosion products on both steel and zinc surfaces. (C) 2016 Elsevier Ltd. All rights reserved.

In this work the protective effect of layered double hydroxide (LDH) films directly grown on the surface of 2024-T3 aluminium alloy is investigated using electrochemical impedance spectroscopy (EIS) and the scanning vibrating electrode technique (SVET). The SVET results focused on the localised nature of the corrosion process and are in agreement with the global response measured by EIS. Furthermore, the evolution of active corrosion protection rendered by LDH films is surveyed at microscale for the first time for long immersion periods in NaCl solution and in the presence of induced defects. The quantitative information provided by SVET is discussed and a parameter to describe the degree of corrosion localisation is introduced based on LDH systems.

In this work the protective effect of layered double hydroxide (LDH) films directly grown on the surface of 2024-T3 aluminium alloy is investigated using electrochemical impedance spectroscopy (EIS) and the scanning vibrating electrode technique (SVET). The SVET results focused on the localised nature of the corrosion process and are in agreement with the global response measured by EIS. Furthermore, the evolution of active corrosion protection rendered by LDH films is surveyed at microscale for the first time for long immersion periods in NaCl solution and in the presence of induced defects. The quantitative information provided by SVET is discussed and a parameter to describe the degree of corrosion localisation is introduced based on LDH systems. (C) 2016 Elsevier Ltd. All rights reserved.

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.

In this work active corrosion protection of AA2024 by a bilayer system consisting of a LDH (layered double hydroxides) conversion layer coated by a sol-gel film was studied. Impedance and Scanning vibrating electrode technique (SVET) studies demonstrated an efficient active corrosion protection and self-healing abilities of the systems containing LDH layer loaded with vanadate corrosion inhibitor. Microstructural and chemical analysis of the surface after corrosion testing showed accumulation of chlorine signal in LDH coatings. The scavenging of chlorides and release of vanadate inhibitor from LDH can explain high efficiency of corrosion inhibition of AA2024 by the novel protective system.

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.

An active protective coating for ZE41 magnesium alloy was produced by sealing an anodic layer, loaded with 1,2,4-triazole, with a sol-gel film. An anodic oxide layer was formed using PEO in a silicate-fluoride alkaline solution. This thin (1.8 mu m) porous PEO layer was impregnated with corrosion inhibitor 1,2,4-triazole and sealed with a silica-based sol-gel film modified with titanium oxide. For the first time it was demonstrated that this relatively thin PEO-based composite coating revealed high barrier properties and provided superior protection against corrosion attack during 1 month of continuous exposure to 3% NaCl. A scanning vibrating electrode technique showed a sharp decrease (100 times) of corrosion activity in micro defects formed in the 1,2,4-triazole doped composite coating, when compared to blank samples.