M. Deyá

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.

Calcium tripolyphosphate: An anticorrosive pigment for paint

The objective of this work was to evaluate the performance of calcium tripolyphosphate in anticorrosive paints. Its anticorrosive properties were studied in pigment suspensions and in solventborne paints with 10% and 30% of the pigment by volume and a pigment volume concentration/critical pigment volume concentration (PVC/CPVC) equal to 0.8. The behavior of paints formulated with epoxy and alkyd resins was assessed by accelerated (salt spray cabinet and humidity chamber) and electrochemical tests (corrosion potential, ionic resistance, and polarization resistance).Calcium tripolyphosphate was proven to inhibit steel corrosion when incorporated in a paint film. Good protection was achieved employing only 10% by volume of the pigment, instead of 30%, as was suggested in the case of phosphates. The anticorrosion protection afforded by alkyd paints was impaired when the pigment content was increased. Epoxy paints seemed to be less sensitive to the pigment content.

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.

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.

Zinc tripolyphosphate: An anticorrosive pigment for paints

SummariesThe aim of this paper was to study the efficiency of zinc tripolyphosphate as an anticorrosive pigment for paints. A procedure to prepare the pigment was outlined and its anticorrosive properties evaluated following the electrochemical behaviour of a steel electrode in pigment suspensions. In a second stage, solvent-borne paints containing barium sulphate, talc and titanium dioxide together with 30 or 10% v/v (by volume) of zinc tripolyphosphate, with respect to 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-polyamide (1:1) resin. 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 zinc tripolyphosphate inhibited corrosion when incorporated into a paint film. It showed an excellent performance when employed with the alkyd resin. Good correlation was obtained between accelerated and electrochemical tests.RésuméCet article a comme but l’étude de l’efficacité du tripolyphosphate de zinc en tant que pigment anticorrosit pour la peinture. Les grandes lignes des procédés de préparation ont été exposées et ses propriétés anticorrosives ont été évaluées selon le comportement d’une électrode d’acier dans des suspensions du pigment. Au cours d’une deuxième étape on a formulé des peintures diluables au solvant et contenant du suitate de barium, du talc, et du dioxide de titane aussi bien que 30 ou 10% v/v du pigment tripolyphosphate de zinc par rapport au contenu total en-pigments dans le rapport de 0.8 CPV/CPVC (concentration pigmentaire volumique/concentratation pigmentaire volumique critique) Deux résines ont été choisies pour former le film, l’une alkyde, l’autre une époxy-polyamide (1:1). La performance des peintures anticorrosives qui en provenaient a été évaluée par des essais accélérés (enceintes d’essais en brouillard salin et en humidité) et par des essais électrochimiques (potentiel de corrosion, résistance ionique, résistance de polarisation).Nous avons démontré que le tripolyphosphate de zinc quand il est incorporé à un film de peinture inhibe la corrosion. Il a fait preuve d’une performance excellente quand il était employé avec la résine alkyde. Il y avait une bonne corrélation entre les résultats des essais accélérés et ceux des essais électrochimiques.ZusammenfassungDer Zweck dieser Studie war es, die Wirksamkeit von Zinktripolyphosphat als ein korrosionshemmendes Pigment für Anstrichfarben zu untersuchen. Wir stellten zunächst eine Methode vor, um das Pigment herzustellen, und bewerteten dann seine antikorrosiven Eigenschaften mittels der elektrochemischen Reaktion einer Stahl-Elektrode in einer Pigmentsuspension.In einem zweiten Schritt wurden lösungsmittelhaltige Farben hergestellt, die Bariumsulfat, Talk und Titaniumdioxid, sowie einen Anteil von 10% v/v oder 30% v/v des Zinktripolyphosphat (bezogen auf den Gesamtpigmentgehalt) enthielten. Die Farben hatten ein Verhältnis von Pigmentvolumenkonzentration zu kritischer Pigmentvolumenkonzentration von 0.8. Wir verwendeten zwei verschiedene Harze als Filmbildner in diesen Farben: ein Alkyd und ein Epoxy-Polyamid (1:1) Harz. Die Wirksamkeit des enstandenen korrosionshemmenden Lackes wurde mittels beschleunigten Tests (Salzsprüher und Luftfeuchtigkeitsräume) und eletrochemischer Tests (Korrosionspotential, ionischer Widerstand, Polarisationswiderstand) ermittelt.Die Tests untermauerten, daß Zinktripolyphosphat als Bestandteil einer Farbe oder eines Lackes korrosionshemmed wirkt. Zinktripolyphosphat zeigte eine hervorragende Leistung als Bestandteil eines Lackes auf Alkydbasis. Wir fanden auch eine gute Korrelation zwischen den beschleunigten Tests und den elektrochemischen Tests.

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.