Corrosion – inhibiting properties of molybdenum-containing pigments in coatings

Abstract

Purpose -Synthesise anticorrosion pigments containing molybdenum for paints intended for corrosion protection of metals.Design/methodology/approach -The anticorrosion pigments were prepared by hightemperature solid-state synthesis from the appropriate oxides, carbonates, and calcium metasilicate. Stoichiometric molybdates and core-shell molybdates with a non-isometric particle shape containing Ca, Sr, Zn, Mg, and Fe were synthesised. 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 vol.% 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. Findings -The molybdate structure of each pigment prepared was elucidated. The core-shell molybdates exhibit a non-isometric particle shape. The pigments prepared were found to impart a very good anticorrosion efficiency to the paints. A high anticorrosion efficiency was found with the pigments Fe 2 (MoO 4 ) 3 and Fe 2 (MoO 4 ) 3 /CaSiO 3 and with Mg and Zn molybdates.Practical implications -The pigments can be used for the formulation of paints intended for the corrosion protection of metals. The pigments also improve the paints´ physical properties.Originality/value -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 the anticorrosion pigments which are free from heavy metals and are acceptable from the aspect of environmental protection. Moreover, the core-shell molybdates, whose high efficiency is comparable to that of the stoichiometric molybdates, have lower molybdenum contents.

Evaluation of Corrosion Resistance of Corrosion Inhibitors for Concrete Structures by Electrochemical Testing in Saturated Ca(OH)2Solutions with NaCl and Na2SO4

“…Inhibitors prevent the onset of corrosion by increasing the concrete pH or by fixating harmful ions that can cause the corrosion of steel [1,2]. Frequently used corrosion inhibitors include inorganic nitrites [3][4][5], inorganic phosphate [6] and molybdenum [7], monofluorophosphate that is applied to the surface of the concrete [8], and organic inhibitors, such as alkanolamine and amine groups [9][10][11][12][13][14][15].…”