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Abstract: Design, development and scale-up of environmentally friendly coatings are very important in order to replace chromate based coatings for aluminium alloys. Barrier properties, paint adhesion and possibly self-healing ability are relevant aspects for replacement of chromate-based pre-treatments. Sol–gel materials are candidates for use in protective coating applications, as it is possible to form highly adherent and chemically inert oxide films on metal substrates. ZrO2 based pre-treatments were developed by means of sol–gel-technology. ZrO2 films were deposited on AA2024 by means of dip-coating technique in sol obtained from metal-organic precursor in an organic solvent. In addition, an inorganic salt was employed as Zr precursor in an aqueous solution. Cerium nitrate was introduced in multilayer films in order to improve the corrosion behaviour. In addition, AA2024 substrates pre-treated with ZrO2 films were painted with an organic primer and top coat in order to evaluate the electrochemical behaviour of painted systems. The morphology, thickness and composition of ZrO2 films deposited on AA2024 were investigated by means of SEM-EDXS and GDOES (glow discharge optical emission spectroscopy). The electrochemical behaviour of ZrO2 pre-treatments was studied by means of potentiodynamic polarization measurements. AA2024 samples pre-treated and painted with an organic coating were subjected to paint adhesion tests and electrochemical characterization by means of electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: Scanning electrochemical microscopy has been employed to obtain spatially-resolved information regarding surface topology, water uptake and blister formation at intact coatings, as well as the onset and progress of corrosion reactions within coating defects. Topographical lines and maps as well as chronoamperometric plots were measured during operation in the feedback mode. Next, the release of metal ions at the anodic sites and the consumption of oxygen at the cathodic sites developed in holidays could be monitored during operation in the generator–collector mode. Furthermore, the surface topography of defective coatings was imaged by using the redox competition mode. [ABSTRACT FROM AUTHOR]

Abstract: Organic coating in combination with sacrificial metal coating is the most popular method of protecting steel strips against atmospheric corrosion. Experiences over the years have proven that such duplex coating systems are best suited for the coil industry for the long term corrosion protection of steel. The excellent corrosion resistance of such systems has been attributed to the synergy between the cathodic protection provided by the sacrificial coating of zinc alloys and the combined barrier resistance of the metal and organic coatings. Traditionally continuously hot dip zinc-coated steels are used for such applications. However, off late the quest for further extending the longevity of the coil coatings has led to the replacement of the zinc coating with a host of other hot dip zinc–aluminium alloy coatings such as Galvalume®, Galfan®, ZAM®, SuperDyma®, etc. Each of these metal coatings has its own unique metallurgical features in terms of flexibility, bonding, microstructure and electrochemical characteristics which may significantly influence the performance of the organic coatings applied over it. This paper looks into the various aspects of these features of the hot dip coatings on the corrosion performance of the pre-painted steel strips. For simplicity only polyester paint system, the work horse of the coil industry, is considered. [Copyright &y& Elsevier]

Abstract: Permanganate-based conversion treatments incorporating silica nano-particles+nitrate ions or other inhibitive additives have been examined by corrosion and adhesion tests on samples coated with paint and by polarisation measurements on treated, but uncoated AA 3003 panels. Although electrochemical behaviour is not improved by addition of the silica nano-particles, in many cases they substantially improve the performance of PVDF-coated samples in adhesion and accelerated corrosion tests. [Copyright &y& Elsevier]

Purpose - To synthesise calcium titanate with a perovskite structure as an anticorrosion pigment for metal protecting paints. Design/methodology/approach - Calcium titanate was synthesised from titanium dioxide and calcium carbonate at high temperature. The pigment obtained was characterised by means of X-ray diffraction, particle size distribution measurement and scanning electron microscopy. The pigment obtained was further characterised with regard to the parameters required for paint formulation; its specific mass was determined by oil consumption and critical pigment volume concentration. The synthesised calcium titanate was used to prepare epoxy coatings with varying contents of the anticorrosion pigment. The coating was tested for physical-mechanical properties and in corrosive atmospheres. The results were compared with titanium dioxide that served as a starting material for calcium titanate preparation. Findings - Calcium titanate was prepared from materials that do not add any impurities to the anticorrosion properties of the pigment. It was identified that calcium titanate of perovskite structure is a highly efficient anticorrosion pigment for paints. Practical implications - Calcium titanate can be utilised for the preparation of anticorrosion paints to protect metal bases from corrosion. Originality/value - The method of synthesising calcium titanate as an anticorrosion pigment is new. The literature has not yet described the use of calcium titanate as a pigment with inhibitive properties in paints. From an ecologic standpoint, the application of a new anticorrosion pigment for paints presents a highly positive trend. [ABSTRACT FROM AUTHOR]