G. Blustein

The influence of the anion type on the anticorrosive behaviour of inorganic phosphates

The objective of this work was to study the efficiency of the anticorrosive pigments obtained by substituting the phosphate anion in zinc phosphate with other anions such as tripolyphosphate and pyrophosphate. A procedure to prepare the pigments is outlined and their anticorrosive properties were evaluated following the electrochemical behaviour of a steel electrode in pigments suspensions. In a second stage, solvent-borne paints with 30% by volume (v/v) of the pigment, with respect of the total pigment content, and PVC/CPVC (pigment volume concentration/critical pigment volume concentration) ratio 0.8 were formulated. Two resins were chosen as film forming materials: an alkyd and an epoxy one. The performance of the resulting anticorrosive paints was assessed by accelerated (salt spray and humidity chambers) and electrochemical tests (corrosion potential, ionic resistance and polarisation resistance). It was demonstrated that the substitution of the phosphate anion by tripolyphosphate or pyrophosphate anions may give rise to effective anticorrosive pigments for paints. The essays performed with pigments suspensions suggested that zinc pyrophosphate has the best anticorrosive properties. The anticorrosive behaviour of the pigments in paints was found to depend on the resin employed to formulate the coatings. Good correlation was obtained between accelerated and electrochemical tests.

The influence of the solubility of zinc phosphate pigments on their anticorrosive behaviour

The objective of this work was to study the anticorrosive behaviour of three commercial pigments containing micronized zinc phosphate. The chemical analyses of the pigments were carried out in the laboratory to characterise them with respect to their composition and soluble matter. It was proposed to check pigments’ efficiency in solvent‐borne paints with 30 per cent v/v of the pigment by volume and a pigment volume concentration/critical pigment volume concentration ratio (PVC/CPVC) equal to 0.8. The behaviour of paints formulated with two binders (alkyd and epoxy) was assessed by accelerated (salt spray cabinet, humidity chamber and accelerated weathering) and electrochemical (corrosion potential, ionic resistance and polarisation resistance) tests. It was demonstrated that pigment performance is highly influenced by their solubility which, in turn, could influence the formation of the protective layer on the metal substrate. Good correlation was obtained between salt spray and electrochemical tests.

Core-shell pigments in antifouling paints

SummariesMarine fouling is the result of the settling and subsequent growth of organisms on surfaces immersed in seawater. Fouling of ships’ hulls has been traditionally controlled through the use of toxic antifouling paints, but increased ecological awareness and the strict regulations of biocides used in such paints have led to the development of low toxic content or non-toxic coatings to control fouling.Results of investigations on the performance of five antifouling formulations in exposure trials carried out at Mar del Plata harbour (Argentina) are presented. The tests have revealed that these paints, which were formulated with a combination of a thin layer or shell of toxic pigment (cuprous thiocyanate) surrounding a core particle of non-toxic pigment (herein termed core-shell pigments), prevented the settlement of foulers, reducing costs and marine pollution.RésuméLa salissure provient du dépôt des organismes et de leur croissance subséquente sur des surfaces immergée dans l’eau de mer. Traditionnellement, on a contrôlé la salissure des coques de navires en utilisant des peintures antisalissure toxiques. mais la sensibilisation intensififée aux considérations écologiques et la stricte règlementation des biocides utilisées dans de telles peintures a mené au développement de revêtements non-toxiques ou à faible toxicité, pour contrôler la salissure.Les résultats de l’examen de la performance de cinq formulations antisalissure au cours des essais d’exposition au port de Mar del Plata (Argentine) sont présentés. Les essais ont révélé que ces peintures, qui sont formulées avec la combinaison d’une fine couche ou “shell” de pigment toxique (thiocyanate de cuivre) qui recouvre une particule centrale de pigment non-toxique (dénommée “core/shell pigments” dans cet article), ont empêché le dépôt de la salissure, réduisant ainsi la pollution marine et les frais.ZusammenfassungOberflächen die in Meereswasser ausgesetzt sind werden gerne von Algen und anderen Meeresbewohnern besiedelt. Dieser Vorgang wurde in der Vergangenheit hautsächlich durch die Verwendung von Anti-Fouling-Anstrichen verhindert, aber mit vermehrter Rücksicht auf das Ökosystem und strengere Richtlinien für die Verwendung von Bioziden in Anstrichen hat dazu geführt, daß neue, ungiftige or nur leicht giftigen Anstriche für Schiffe entwickelt wurden.Wir führten Tests an fünt Anti-Fouling-Formulierungen im Mar del Plata Hafen von Argentinien durch, und stellen die Ergebnisse hier vor Unsere Tests ergaben, daß diese Anstriche, die aus einer Kobination von einer dünnen Lage eines giftigen Pigmentes ([cuprous] Thiocyanat) auf einem ungiftigen Pigmentkern bestanden, die Ansiedlung von Meerespflanzen und-tieren verhinderten, und damit die Kosten und die Meeresverschmutzung verminderten.

Zinc Molybdenum Phosphate: An Effective Anticorrosive Pigment for Solvent and Water Borne Paints

The anticorrosive properties of two commercially available phosphate pigments, with different molybdenum content in their composition, have been investigated. The anticorrosive properties of the pigments were assessed by electrochemical techniques in pigment suspensions and then in solvent and water-borne paints. The paints contained 30% by volume of anticorrosive pigment, with respect to the total pigment content. The anticorrosive performance of paints formulated with different binders alkyd, epoxy and water-borne epoxy has been evaluated by accelerated (salt spray cabinet and humidity chamber) and electrochemical tests (corrosion potential and ionic resistance). It was found that paints formulated with both pigments behaved satisfactorily in accelerated tests and both provided very good anticorrosive protection to steel. The pigment with the highest molybdenum content showed a better performance in water-borne paints.

Aluminum Basic Benzoate-Based Coatings: Evaluation of Anticorrosion Properties by Electrochemical Impedance Spectroscopy and Accelerated Tests

Abstract Insoluble metallic benzoates can be prepared from the corresponding soluble salts. Soluble benzoates can be used as inhibitors in neutral solutions while insoluble ones can be used as anti...

Alkyl 2-furoates obtained by green chemistry procedures as suitable new antifoulants for marine protective coatings

In search of new sustainable alternatives to reduce the use of metallic antifouling pigments in marine paints, three n-alkyl 2-furoates were synthesized by safe procedures framed within the green chemistry concepts. These compounds were characterized by current organic analysis, and their antifouling properties were first evaluated on Artemia salina nauplii in the laboratory. Then, antifouling paints formulated with these compounds were assayed in a marine environment. Both laboratory and field tests indicate that n-alkyl 2-furoates have strong antifouling activity and are safe chemicals for marine paints.

Estudio de las Propiedades Anticorrosivas del Benzoato de Hierro (III) en Pinturas Base Solvente

La accion inhibidora del benzoato de hierro en electrodos de acero SAE 1010 en contacto con una suspension acuosa fue estudiada mediante ensayos electroquimicos. Paralelamente, la eficiencia anticorrosiva de este producto incorporado a cubiertas organicas base solvente fue evaluada mediante ensayos de envejecimiento acelerado (camara de niebla salina y de humedad). La evolucion del comportamiento protector de la cubierta aplicada sobre paneles de acero pintados e inmersos en una solucion 0.5M de NaClO4 fue periodicamente monitoreada por espectroscopia de impedancia electroquimica. Los resultados obtenidos indican que las pinturas formuladas con benzoato ferrico presentan una capacidad anticorrosiva comparable a las formuladas con fosfato de cinc.