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To study the effect of feldspars as inorganic filler on the mechanical and dielectric properties of epoxy coatings.

Coating systems used were of either filler‐free epoxy resin (as reference), or epoxy resin filled with feldspars powder at four different levels by weight. Mechanical properties of the coatings were evaluated via damping hardness and abrasion and impact resistance measurements. Electrochemical impedance spectroscopy measurements were used for the evaluation of the dielectric properties while visual observations of the test panels after salt‐spray test were also made.

The addition of 15 per cent w/w feldspars resulted in a formulation giving the most positive results, e.g. improvement of the coating's mechanical characteristics and dielectric behaviour similar to that of filler‐free epoxy coatings. Practically comparable to this behaviour was that possessed by coatings with 30 per cent w/w feldspars, while further increase of the feldspars content resulted either in a reduction in the extent of the enhancement of the mechanical behaviour or even in a worsening of both mechanical and dielectric characteristics.

Feldspars are the most abundant group of minerals in the earth's crust; it is an inorganic, environmentally friendly material, which exhibits high Mohs hardness. The effects of feldspars in improving the mechanical characteristics of organic coatings, while not causing any reduction in the anticorrosive performance of the polymeric matrix was found through the study.

The purpose of this paper is to study of the effect of carboxylic acids additions to the anodising bath on the subsequent corrosion and stress corrosion cracking (SCC) tendencies of anodised 1050 Al‐Alloy in 3M NaCl solution.

The study was carried out using SCC tests and electrochemical cyclic potentiodynamic measurements at a high or a slow scan rates. The anodic coatings were prepared electrolytically in a bath of 4 M H2SO4, with and without additions of 0.015 M oxalic, malonic, tartaric, maleic, or citric acids. The consequent thicknesses and packing densities of the coatings were measured.

The SCC behaviour was found to vary with both anodising conditions and stress level. The addition of carboxylic acids in the anodising bath increased the protective properties of the coating. In corrosion conditions without stress, the addition of the carboxylic acids decreased the susceptibility to pitting corrosion, the effect depending on the presence or absence of corrosion products. The addition of the carboxylic acids during anodising leads to the formation of less porous and more compact oxide layers and increases the anticorrosive properties of the coatings. The benefits were most pronounced for the coating prepared in the presence of maleic acid.

The belief that the effect of carboxylic acids on the corrosion and SCC behaviour of Al‐Alloys is due to the absorption of these compounds on the metal surface and the formation of complexes on it, depending on the structure and carbonic chain of these compounds, remains yet to be confirmed.

Anodic coatings prepared in an electrolytic bath containing carboxylic acids can be used for the protection of aluminium alloys against corrosion.

The paper provides information regarding the improvement of the anticorrosive properties of electrolytically prepared anodic coatings on aluminium alloys.