Electrosprayed PLGA smart containers for active anti-corrosion coating on magnesium alloy Amlite

A novel self-healing system, consisting of poly(lactic-co-glycolic) acid (PLGA) porous particles loaded with a corrosion inhibitor, i.e. benzotriazole (BTA), has been successfully achieved via direct electro-spray deposition and subsequent epoxy spraying upon magnesium (Mg) alloy AMlite. The two-step process greatly simplified the multi-step fabrication of smart coatings reported previously. The PLGA particles demonstrate rapid response to both water and pH increase incurred by corrosion of Mg, ensuring instant and ongoing release of BTA to self-heal the protective functionality and retard further corrosion. Furthermore, nanopores in the PLGA–BTA microparticles, formed by the fast evaporation of dichloromethane during the electrospray process, also contribute to the fast release of BTA. Using Mg alloy AMlite as a model substrate which requires corrosion protection, potentiodynamic polarisation characterisation and scratch testing were adopted to reveal the anti-corrosion capability of the active coating.

A potential anti-corrosive ionic liquid coating for MG alloy AZ31 in simulated body fluids

Magnesium alloys are attractive materials for biomedical applications, due to their excellent biocompatibility. However, these alloys show fast corrosion rates in the body that limits their clinical applications. Low-toxic ionic liquid (IL) trimethyl(butyl)phosphonium diphenyl phosphate P1444dpp has been investigated to provide corrosion protection for magnesium alloy AZ31 in simulated body fluids (SBFs). This work reports a preliminary exploration of the influence of different treatment temperatures on the corrosion protection properties of IL films for the magnesium alloy AZ31 in SBFs. Results show that the IL treatment at room temperature did not bring significant improvement in the corrosion performance of the AZ31 in SBF. However, when the treatment temperature was increased to 75°C, the IL treatment resulted in a substantial reduction of the corrosion, in particular the reduction of localized pitting corrosion. The influence of ionic liquid treatment on the corrosion performance of the magnesium alloys AZ31 in SBFs has been investigated by electrochemical impedance spectroscopy (EIS) tests and immersion tests.

Corrosion inhibiting coating

The present invention provides a corrosion inhibiting coating comprising a rare earth-based organic compound and/or a combination of a rare earth metal and an organic compound, a method of inhibiting corrosion involving the coating and a method of preparing said coating.

Studying and evaluating anti-corrosion coatings and inhibitors using the wire beam electrode method in conjunction with electrochemical noise analysis

Purpose – To provide a summary of research work carried out mainly in the authors' group for evaluating various protective coatings including rustproofing oils, and also for studying corrosion inhibitors using the wire beam electrode (WBE) method.

Design/methodology/approach – A range of published papers published during the past 15 years was summarised and reviewed. Recent research work in the authors' group was also included, which involved the combined use of the WBE with electrochemical noise analysis and the scanning reference electrode technique.

Findings – The WBE method has been developed into a very useful tool of evaluating the performance of coatings and inhibitors. In particular, The WBE is uniquely applicable for determining the performance of coatings and inhibitors to control localised corrosion.

Research limitations/implications – Focusing mainly on recent research.

Practical implications – A useful source of information for researchers and graduate students working in the areas of organic coating and inhibitor research.

Originality/value – The first summary or review on this research topic.

Recent developments in characterising electrodeposition of anti-corrosion coatings using the wire beam electrode method

New progresses have been made during recent years in the application of the wire beam electrode (WBE, a coupled multielectrode array) for studying electroplating of metallic coatings, for monitoring the electrodeposition of polymer coatings, and for evaluating the performance of anti-corrosion coatings. The WBE allows localized electrode processes to occur over different locations of its surface under external anodic or cathodic polarization and permits monitoring of nonuniform electrodeposition processes. Several typical experiments are presented in this paper. One sample experiment is the characterization of nonuniform electroplating of nickel coating, which was achieved by mapping the distributions of currents over a WBE surface that was under cathodic polarization. Various characteristic current distribution patterns, which indicate different electrodeposition mechanisms or low covering-power, have been observed. These patterns were found to correlate with the effects of several affecting factors such as electrolyte concentration, temperature and agitation flow. Another sample experiment is the investigation of nonuniform anodic electrodeposition of polyaniline (PANI) coatings and the understanding of their anti-corrosion performance and mechanisms. Anodic polarization currents were measured from various locations over the WBE surface in order to produce anodic polarization current maps under PANI deposition.

In situ measurement of pipeline coating integrity and corrosion resistance losses under simulated mechanical strains and cathodic protection

A novel experimental assembly consisting of a specially designed tensile testing rig and a standard electrochemical flat cell has been designed for simulating buried high pressure pipeline environmental conditions in which a coating gets damaged and degrades under mechanical strain, and for studying the influence of mechanically induced damages such as the cracking of a coating on its anti-corrosion property. The experimental assembly is also capable of applying a cathodic protection (CP) potential simultaneously with the mechanical strain and environmental exposure. The influence of applied mechanical strain as well as extended exposure to the corrosive environment, coupled with the application of CP, has been investigated based on changes in electrochemical impedance spectroscopy (EIS). Preliminary results show that the amplitude of the coating impedance decreases with an increase in the applied strain level and the length of environmental exposure. The EIS characteristics and changes are found to correlate well with variations in coating cracking and degradation features observed on post-test samples using both optical microscopy and scanning electron microscopy. These results demonstrate that this new experimental method can be used to simulate and examine coating behaviour under the effects of complex high pressure pipeline mechanical, electrochemical and environmental conditions.

In situ synthesis of TiC-Fe composite overlays from low cost TiO 2 precursors using plasma transferred Arc deposition

A direct conversion of TiO2 into TiC during plasma transferred arc deposition is a cheap and novel approach to produce wear resistant coatings. The present study explored the use of a low cost titanium ore as precursor for titanium carbide in metal matrix composite overlays. The deposited layers were characterized using optical microscopy, scanning electron microscopy, x-ray diffraction and microhardness testing. A carbothermic reduction of the titanium oxides took place during the deposition of the coating by plasma transferred arc. The overlays produced in this way consisted of fine titanium carbides evenly dispersed in an iron matrix. The opportunities and limitations of this approach are discussed.