Corrosion – inhibiting properties of molybdenum-containing pigments in coatings

Purpose – This paper aims to synthesise anticorrosion pigments containing molybdenum for paints intended for corrosion protection of metals. Design/methodology/approach – The anticorrosion pigments were prepared by high-temperature 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 scanning electron microscopy. Paints based on an epoxy resin and containing the substances at a pigment volume concentration of 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. 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 Fe2(MoO4)3 and Fe2(MoO4)3/CaSiO3 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.

Rhabdovirus en papayo (Carica papaya L.) en el sureste de México.

In commercial papaya plantations of the southeastern Mexican States of Chiapas, Tabasco, Oaxaca and Veracruz, 0.1 to 10% incidence of plants with peculiar symptoms were observed, sampled and studied for viral infections. Stem internodes were shorter than normal, the leaves were smaller and harder. There was necrosis in younger leaves, petioles were shorter and curved with reddish-gray stripes, and flower and small fruits were standing upright. In negative staining bullet-shaped particles were observed, as well as rod shaped and isometric ones. Bacilliform particles with a perinuclear membrane were also observed within the nucleus in ultra thin preparations, and stained preparations inclusions were present in the nucleus of the floem. The disease could not be mechanically nor seed transmitted. The incidence was higher in the summer than in the winter. All the description coincided with an infection by the papaya apical necrosis Rhabdovirus, although mixed with the papaya ringspot Potyvirus and with an isometric particle not identified.