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The presence of soluble salts, especially chlorides and sulphates, at the metal/paint interface usually causes premature deterioration of the paint system. In practice, soluble salts are found heterogeneously distributed in the steel corrosion products layer and are frequently located at the base steel/rust layer interface. However, in most of the research studies carried out with the aim of establishing critical concentration levels for different paint systems, panels have been prepared by dosing the saline contaminant in an uniform way across flat and unrusted steel surfaces. In order to resolve this problem, an attempt has been made to reproduce the atmospheric corrosion process of steel in environments contaminated with SO₂ and Cl⁻, using a salt fog cabinet for the case of chlorides, and a Kesternich type cabinet for sulphates.

Aluminium pigmented chlorinated rubber coatings, widely used for steel ship protection, can be bleached when exposed to total immersion conditions. A deep study on the development of the decolouration processes of these coatings, applied on rolled steel specimens exposed to total immersion conditions in aqueous solutions with different salinity, has been carried out. The relationship between external salinity and contamination by sodium chloride of the steel/coating interface in the bleaching processes has been analysed. Besides, the influence of the osmotic processes in the coating bleaching has been established. Periodic visual inspections of the coating films, together with a deep analysis of the coating microstructure, by means of optical microscopy and scanning electron microscopy provided with microsonde analysis, were used. The bleaching processes of the coatings mainly depend on the salinity of the external solution, while the influence of the steel/coating interface contamination is not relevant.

Zinc‐rich paints (ZRP) are considered to be an important technological development for corrosion protection. The percentage of zinc corroded during the cathodic protection stage of zinc‐rich coatings is relatively small in comparison with the initial total zinc content. This fact, together with the relatively high cost of zinc, the desire to avoid some interferences with the welding process, and the sedimentation of the zinc dust in cans, are some of the reasons to search for co‐pigments (extenders) in ZRP formulas. In the paper the anti‐corrosive performance of ZRP formulas including a new conductive inorganic co‐pigment of low specific density (SVUOM) are shown.

In anticorrosive painting of structural steel the preparation of the metallic surface prior to the application of the organic coating is an important, if not more so, as the selection of the paint system.

The purpose of this paper is to present a laboratory accelerated periodic immersion wet/dry cyclic corrosion test, reflecting the alternate wet/dry process during the atmospheric exposure of metallic materials, which can be applied to evaluate the atmospheric corrosion resistance (ACR) of weathering steels in a very short period.

This test method uses 0.01 M sodium bisulfite aqueous solution with pH 4.4 as the immersion medium, simulating the notable characteristics of sulfur dioxide pollutant in industrially polluted atmospheres. During the test process, the tested specimens are immersed into the solution for 12 minutes, immediately followed by the subsequent drying process for 48 minutes, and such alternate process consists of a cyclic period, i.e. 1 hour. As a result of this procedure, a relative corrosion rate is defined to determine the ACR. To determine a preferred test period, different test periods including 72 and 200 hours were compared.

Compared with several other commonly used test methods, it was confirmed that the relative ACR of various steels can be determined after testing for only 72 hours. The constituent of the corrosion products, i.e. the rust layer, was consistent with that formed after long-term exposure in a typical outdoor atmospheric environment.

The test method enables comparative testing for ranking the ACR of weathering steel during the development of new weathering steels.

This study aims to investigate the role of aluminium (Al) in marine environment and the corrosion mechanism of galvalume coatings by conducting accelerated experiments and data analysis.

Samples were subjected to accelerated corrosion for 136 days via salt spray tests to simulate the natural conditions of marine environment and consequently accelerate the experiments. Subsequently, the samples were examined using various test methods, such as EDS, scanning electron microscopy (SEM), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS), and the obtained data were analysed.

Galvalume coatings comprised interdigitated zinc (Zn)-rich and dendritic Al-rich phases. Corrosion was observed to begin with a Zn-rich phase. The primary components of the corrosion product film were Al₂O₃ and Zn₅(OH)₈Cl₂·H₂O. It was confirmed that the role of Al was to form a dense protective film, thereby successfully blocking the entry of corrosive media and protecting the iron substrate.

This study provides a clearer understanding of the corrosion mechanism and kinetics of galvalume coatings in a simulated marine environment. In addition, the role of Al, which is rarely mentioned in the literature, was investigated.

This paper aims to synthesize anticorrosion pigments containing tungsten for paints intended for corrosion protection of metals.

The anticorrosion pigments were prepared by high-temperature, solid-state synthesis from the respective oxides, carbonates and calcium metasilicate. Stoichiometric tungstates and core-shell tungstates with a nonisometric particle shape containing Ca, Sr, Zn, Mg and Fe were synthesized. The pigments were examined by X-ray diffraction analysis and by scanning electron microscopy. Paints based on an epoxy resin and containing the substances at a pigment volume concentration (PVC) = 10 volume per cent were prepared. The paints were subjected to physico-mechanical tests and to tests in corrosion atmospheres. The corrosion test results were compared to those of the paint with a commercial pigment, which is used in many industrial applications.

The tungstate structure of each pigment was elucidated. The core-shell tungstates exhibit a nonisometric particle shape. The pigments prepared were found to impart a very good anticorrosion efficiency to the paints. A high efficiency was demonstrated for the stoichiometric tungstates containing Fe and Zn and for core-shell tungstates containing Mg and Zn.

The pigments can be used with advantage for the formulation of paints intended for corrosion protection of metals. The pigments also improve the paints’ physical properties.

The use of the pigments in anticorrosion paints for the protection of metals is new. The benefits include the use and the procedure of synthesis of anticorrosion pigments which are free from heavy metals and are acceptable from the environmental protection point of view. Moreover, the core-shell tungstates, whose high efficiency is comparable to that of the stoichiometric tungstates, have lower tungsten content.

The paper developed a novel gallic acid-based rust conversion emulsion (RCE) that is applied in the treatment of rusted steels. The purpose of this paper is to investigate the methods for the synthesis of RCE and study the mechanism of rust conversion.

Conversion emulsion was prepared using styrene, acrylate and self-developed gallic acid (GA)-based rust converter (GRC) via seed emulsion polymerisation. The polymerisable GRC was synthesised by the ring-opening reaction of glycidyl methacrylate with natural GA. The effects of the GRC dosage and its feeding modes on the RCE synthesis were analysed. The corrosion resistance, surface morphology, composition and mechanism of rust conversion coatings were studied using electrochemical tests, scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively.

The results showed that conversion coating on rusted steels treated with RCE, with various dosages of GRC (weight per cent), synthesised using seed emulsion polymerisation, exhibited the best adhesion and corrosion resistance. Raman spectroscopy revealed that RCE converted the original multiphase rust into stable crystalline phases of α-Fe₂O₃ and Fe₃O₄. According to XPS and energy dispersive X-ray analysis, the phenolic hydroxyl groups of RCE were proposed to chelate with Fe ions to form macromolecular ferrum compounds.

The pre-rusted steels demonstrated a better corrosion resistance than rust-free steels after treatment with RCE.

The paper developed a novel GA-based RCE with high efficiency and environment-friendly method.

This work is expected to replace the conventional rust conversion paints and cause a significant impact on extending the service life of rusted steels.

This paper aims to access the protective function of hybrid sol-gel coatings deposited on 304L stainless steel substrate in silane solutions containing a mixture of tetraethoxysilane, methyltriethoxysilane and glycidyloxypropyltrimethoxysilane with different pH values during various immersion periods.

The 304L stainless steels coated through 10 and 30 s of immersion in the silane solutions with pH values of 2.1 and 2.8 were exposed to NaCl solution. The corrosion resistance of the coated substrates was studied through taking advantage of electrochemical noise method as well as atomic force microscopy (AFM), water contact angle and field emission-type scanning electron microscopy (FESEM) surface analysis.

The electrochemical current noise, PSD (I) plot, noise resistance and characteristic charge as parameters extracted from electrochemical noise method indicated the superiority of eco-friendly silane coating deposited on the substrate surface during 10 s exposure to the solution, due to the film uniformity and homogeneity as confirmed by FESEM and AFM. Moreover, immersion of the stainless steel in the silane solution with pH 2.1, characterized by higher hydrolysis ratio, led to more effective corrosion control in the NaCl electrolyte according to the results of electrochemical noise and FTIR measurements.

The noise resistance and characteristic charge as electrochemical noise parameters were only used in this research to evaluate the protective behavior of the water-based silane sol-gel coatings. Future studies should examine the correlation between electrochemical noise data and the parameters extracted from other electrochemical methods, e.g. electrochemical impedance spectroscopy.

The data obtained in this research may provide an effective approach based on electrochemical noise method to screen the silane sol-gel coatings for protection of metallic substrates against corrosion.

According to the literature, no report can be found studying the effect of immersion time on a silane solution, including glycidyloxypropyltrimethoxysilane, tetraethoxysilane and methyltriethoxysilane, as well as the silane solution pH on the corrosion resistance of 304L stainless steel in NaCl solution through electrochemical noise method.

A barrier type of finish coat on zinc‐rich primers can effectively prevent corrosion on mild steel structures in marine environments. Chlorinated rubber is well known for its impermeability of water vapours and corrosive ions. Micaceous iron oxide (MIO) and titanium dioxide (Ti0₂) are the best barrier pigments available in the world. The chlorinated rubber based top coatings have been prepared by incorporating these two pigments separately and applied over three types of zinc‐rich primers (ZRP) (butyl titanate ZRP, cashew nut shell liquid ZRP and epoxy polyamide ZRP). The electro chemical aspects of protection afforded by these coating systems have been evaluated on mild steel substrate in 3 percent NaCI solution by potential‐time, polarisation and impedance techniques. This study revealed an interesting correlation between the polarisation and impedance observations. The inorganic ZRP with top coated systems behave differently to organic ZRP with top coated systems. The MIO pigmented finish coat affords equally higher duration of protection of steel substrate from corrosive saline environment, even though the PVC value is considerably lower than the TiO₂ pigmented top coat systems.