B. del Amo

Study of the anticorrosive properties of zinc phosphate in vinyl paints

Red lead and zinc chromates are doubtless efficient pigments to protect painted metals against corrosion. Their use in paint formulation is being restricted due to environmental concerns. Inorganic phosphates, especially zinc phosphate, have been suggested to replace those pigments. As data presented in the literature are not conclusive, anticorrosive paints formulated with micronized zinc phosphate and vinyl binders have been studied. The principal variables considered were the pigment volume concentration/critical pigment volume concentration (PVC/CPVC) relationship and the content of anticorrosive pigments. Accelerated tests (salt spray and humidity chambers) as well as film adhesion and electrochemical measurements were performed to evaluate the paints anticorrosive performance. Results were compared with a reference paint containing zinc chromate. It was established that paints formulated with an acid resin, containing 30% zinc phosphate by volume and a PVC/CPVC ratio of 0.8‐0.9 showed good anticorrosive behaviour.

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.

High performance water-based paints with non-toxic anticorrosive pigments

Legal restrictions have impelled the replacement of solvent-borne resins and of toxic chromates and lead-bearing pigments in the elaboration of paints. Water-based anticorrosive paints have come a long way to improve their efficiency but their behaviour is said to be poorer than that of solvent-based paints. Nevertheless, recent advances in water-borne technologies have now resulted in improved resin systems that may be employed to produce heavy-duty coatings. The objective of this paper is to formulate high performance water-borne paints pigmented with non-toxic phosphate inhibitors. The anticorrosive properties of the paints were evaluated by accelerated tests (salt spray and humidity cabinets) and electrochemical tests (electrochemical impedance spectroscopy, EIS). The anticorrosive properties of the pigments were also evaluated by electrochemical tests. It was found that it is possible to formulate high performance anticorrosive paints by selecting adequate water-borne resins and ecological pigments.

Performance of zinc molybdenum phosphate in anticorrosive paints by accelerated and electrochemical tests

This work studied the anticorrosive behaviour of micronized ‘zinc molybdenum phosphate’ (zinc phosphate modified with zinc molybdate). It was proposed to evaluate its efficiency in solvent borne paints with 30 and 15% of the pigment by volume and a pigment volume concentration/critical pigment volume concentration ratio (PVC/CPVC) of 0.8. The behaviour of paints formulated with different binders such as epoxy, chlorinated rubber, vinyl and alkyd resins, was assessed by accelerated (salt spray cabinet and accelerated weathering) and electrochemical tests. Epoxy and chlorinated rubber paints showed the best anticorrosive performance. The inhibitive action of ‘zinc molybdenum phosphate’ was confirmed. Good correlation was obtained between salt spray and electrochemical tests.

A non-toxic antifouling compound for marine paints

SummariesLaboratory tests with the common barnadeBalanus amphitrite showed narcotic effect on nauplii, cyprids and odults of a solution of sodium benzoate in artificial sea water. This effect was faster as the concentration of sodium benzoate was increased. Field trials confirmed it was successfull in preventing barnade deposition on soluble matrix paints formulated with sodium benzoate as the antifouling agent. These results indicate the potential bio-activity of sodium benzoate on fouling organisms.ZusammenfassungLaborversuche mit dem gewöhnlichen Raubenfüsskrebs,Balamus amphitrite, zeigteten die narkotische Wirkung einer Lösung von Natriumbenzoat in kunstlichen Seewasser auf Nouplien, Kypride und Ausgewachsene. Diese Wirkung wurde schneller als die Konzentration Natriumbenzoats vermehrt war. Feldversuche bestättigteten, daß es erfolgreich bei Verhinder ung der Roubehfüsskrebsablagerung auf Farben formuliert mit einer löslichen Matrix auf Natriumbenzoat als Antifoulingmittel wurde. Diese Resultaten zeigen die potentieilen Bioaktivität des Natriumbenzoats auf die Organismen die Bewuchs verursachen.RésuméLes essais au laboratoire sur la bernache ordinaire,Balatus amphitrite, mettent en évidence l’effet narcotique d’une solution du benzoate de sodium en eau de mer artificielle sur nouplii, cyprides et adultes. Cet effet se produisait plus rapidement au fur et a mesure que la concentration de benzoate de sodium se augmentait. Des essais pratiques ont confirmé que ce compose était efficace en empêchant le dépõt des bernaches sur les peintures formulées avec benzoate a sodium en tant qu’agent antifouling au sein du soluble. Ces résultats démontrait la bioactivité potentielle de benzoate de sodium contre des organismes capables d’engendrer les salissures.

Aluminium tripolyphosphate pigments for anticorrosive paints

The efficiency of two anticorrosive pigments containing aluminium polyphosphate was studied. Pigments were analysed by current analytical techniques and characterised by FT‐IR spectrometry. The anticorrosive properties of the selected pigments were evaluated following the electrochemical behaviour of a steel electrode in pigments suspensions. In a second stage, solvent‐borne paints with 30 and 10% v/v of the pigment and PVC/CPVC (pigment volume concentration/critical pigment volume concentration) ratio 0.8 were formulated. Three resins were chosen as film forming materials: an alkyd, an epoxy and a vinyl. The performance of the resulting anticorrosive paints was assessed by accelerated (salt spray cabinet and humidity chamber) and electrochemical tests (corrosion potential, ionic resistance and polarisation resistance). The anticorrosive performance of the tested paints was closely related with pigment composition. The nature of the resin was also of importance; in this sense, epoxy paints showed the best anticorrosive performance. Good correlation has been obtained between accelerated and electrochemical tests.

High performance anticorrosive epoxy paints pigmented with zinc molybdenum phosphate

SummariesThe aim of this research was to study the anticorrosive performance of zinc molybdenum phosphate in solvent-borne epoxy paints at two anticorrosive pigment loadings. The effect of incorporating zinc oxide was also studied.The anticorrosive efficiency of the different paint systems was assessed by accelerated and electrochemical tests.ZusammenfassungDer Zweck dieser Forschung war die Korrosionsschutzleistung von Zinkmolybdönphosphat in lösemittelhältigen Epoxidfarben bei zwei Geholte an Korrosionsschutzpigment. Die Wirkung der Einfuhrung von Zinkoxid wurde auch studiert.Die Korrosionsschutzfähigkeit verschiedener Anstrichstoffssyteme wurde durch schnelle und elektrochemische Prüfungen bewertet.ZusammenfassungLe but de ces recherches était l’étude du rendement anticorrosion de zinc molybdène phosphate en peintures époxydiques aux solvants à deux teneurs en pigment anticorrosion. L’efficacité anticorrosion de differents systèmes de peinture était évoluée par des essais accélérés et électrochimiques.

The application of bioactive compounds from the food industry to control mold growth in indoor waterborne coatings

Microbial growth in indoor environments creates health problems, especially in people with asthma; approximately 80% of these patients are allergic to mold. Antimicrobial coatings are formulated to generate surfaces that are easy to clean and may also incorporate active agents, commonly called biocides, which inhibit microbial colonization, subsequent growth and bio-deterioration of the substrates. Some research lines seek to replace traditional organometallic and organochlorines biocides with environmentally acceptable ones. The aim of this research was, primarily, to explore the possible application of different compounds used in food industry like preservatives to be used as antimicrobial additives for antimicrobial coatings. Four biocides were tested against two different ambient molds isolated from an interior painted wall (Chaetomium globosum and Alternaria alternate). The selected biocides were zinc salicylate, zinc benzoate, calcium benzoate and potassium sorbate. The resulting paints were subjected to biological and physical tests (viscosity, hiding power, humidity absorption and biocides leaching rate). Bioassays revealed that zinc benzoate and zinc salicylate resulted active against both fungi.

The mechanism of the anticorrosive action of calcium-exchanged silica

SummariesThe objectives of this work were to study the efficiency and the mechanism of the anticorrosive action of calcium-exchanged silica in paints. The anticorrosive properties of the pigment were evaluated by following the electrochemical behaviour of a steel electrode in the pigment suspension and analysing the protective layer formed on it. In a second stage, solvent-borne paints were formulated with 30% by volume (v/v) of the total pigment content. The selected PVC/CPVC (pigment volume concentration/critical pigment volume concentration) ratio was 0.8. Two resins were chosen as film-forming materials: an alkyd and an epoxy. The performance of the resulting anticorrosive paints was assessed by accelerated (salt-spray and humidity chambers) and electrochemical tests (corrosion potential, ionic and polarisation resistance).It was demonstrated that the anticorrosive performance of paints pigmented with calcium/silica is at least equal or better than that obtained with paints containing zinc phosphate. Good correlation was obtained between accelerated and electrochemical tests.Steel passivation by calcium-exchanged silica is a complex process accomplished by the high pH of the pigment suspension and the deposition of a siliceous film on the steel surface.RésuméLes objectifs de cette étude étaient d’étudier l’efficacité et le mécanisme de l’action anticorrosive dans les peintures de la silice qui a été l’objet d’une échange ionique par le calcium. Les propriétés anticorrosives ont été évaluées selon le comportement électochimique d’une électrode en acier dans la suspension du pigment et l’analyse de la couche protectrice qui s’y est formée. Au cours d’une deuxième étape des peintures diluables au solvant ont été formulées avec 30% en volume (v/v) du contenu pigmentaire total. Le rapport CPV/CPVC (concentration pigmentaire volumique/concentration pigmentaire volumique critique) était de 0.8. Deux résines ont été choisies pour la formation de feuil: une résine alkyde et une résine époxy. La performance des peintures anticorrosives qui en sont provenues a été évaluée par le moyen des essais accélerés (enceintes d’essais en brouillard salin et en humidité) et des essais électrochimiques (potentiel de corrosion, résistance ionique, résistance de polarisation)Il a été démontré que la performance anticorrosive des peintures pigmentées par calcium/silice au moins égalait, ou même éclipsait celle qui était obtenue par les peintures contenant le phosphate de zinc. Il y avait un bonne corrélation entre les essais accélérés et les essais électrochimiques.La passivation des aciers par la silice/calcium est un procédé complex mené à bout grace au pH pigmentaire élevé et à la déposition des feuils siliceux sur la surface de l’acier.ZusammenfassungDas Ziel dieser Arbeit war es, die Wirksamkeit und den Wirkungsmechanismus der antikorrosiven Wirkung von Kalzium-ersetzten Silikaten in Farben zu erforschen. Die antikorrisive Wirkung des Pigmentes wurden mittels der elektrochemischen Reaktion einer Stahlelektrode in der Pigmentsuspension beurteilt und durch eine Analyse der schützenden Schicht die sich auf der Elektrode gebildet hat. In einem zweiten Schritt wurden lösungsmittelhaltige Farben hergestellt mit einem Silikatgehalt von 30% bei Volumen, bezogen auf den gesamten Pigmentgehalt. Wir wählten ein PVC/CPVC (Pigmentvolumenkonzentration zu kritischer Pigmentvolumenkonzentration) Verhältnis von 0.8. Wir verwendeten zwei verschiedene Harze als Filmbildner in diesen Farben: ein Alkyd und ein Epoxidharz. Die Leistung der entstandenen korrosionshemmenden Farbe wurde durch beschleunigte Tests (Salzsprüher und Luftfeuchtigkeitsräume) und eletrochemische Tests (Korrosionspotential, ionischer Widerstand, Polarisationswiderstand) ermittelt.Die Tests zeigten daß die korrosionshemmende Wirkung von Farben mit Kalzium/Silizium genausogut oder besser war als die Leistung von Farben mit Zinkphosphat. Wir fanden auch eine gute Korrelation zwischen den beschleunigten Tests und den elektrochemischen Tests.Die Passivierung von Stahl durch Kalzium-ersetzte Silikate is ein komplizierter Vorgang der durch den hohen pH-Wert der Pigmentsuspension und die Absetzung eines Silizium-haltigen Filmes auf der Stahloberfläche erreicht wird.

Benzoates: a new approach to non‐toxic marine fouling control

Owing to present and expected future regulations on the use of polluting antifouling compounds, there is a growing need for alternative methods for the prevention of biofouling. Some experiments on the effect of iron benzoate, as a possible biocide agent, on nauplii of Balanus amphitrite were carried out. This pigment was used because it is rapidly hydrolysed and consequently it produces a pH decrease. Although anion benzoate has an intense narcotic effect on nauplii, the results clearly demonstrated that the combined action of this compound and a pH decrease (generated by iron benzoate hydrolysis) produce a pronounced antifouling activity, i.e. the synergic effect is greater than separate effects.