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Steel panels must be protected during storage and transportation because they can corrode. This protection used to be afforded by chromate primers, but nowadays tannin-based primers are being studied. These primers are not only used as protection but also as adhesion promoter if the steel surface was not well prepared (presence of oxides or low roughness). The objective of this work was to prepare lanthanum "tannate", employing tara and quebracho tannins. The "tannates" were incorporated in primers formulation and applied on steel SAE 1010 panels (previously exposed to the humidity chamber or with 6 μm of roughness depth). These primed panels were exposed to humidity chamber where corrosion and blistering degrees were evaluated. Adhesion test were done. Electrochemical assays such as ionic resistance and corrosion potential measurements were carried out. Results showed that the adhesion and the barrier properties of the primers were good. Besides, on low roughness steel, the primers diminished the corrosion current. Results were compared with traditional zinc tetroxychromate primer.

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Tannins have been used to replace chromate in wash-primers as a temporary ("in transit") protection for metals. In the present work, the anticorrosive properties of "quebracho colorado" tannins were tested in water solution and in wash primers to protect aluminum alloy 1050. Polarization curves (linear and Tafel) and corrosion potential measurements were done on the alloy in contact with different concentrations of the tannin. A tannin wash primer was prepared and coated panels were tested in 100% humidity chamber (ASTM D 2247) and by electrochemical techniques (linear polarization curves, corrosion potentials and ionic resistances). Chromate and talc primers as well as no-coated aluminum alloy were also tested, as control, to compare the results.

Of two exopolygalacturonases purified and characterized from an Aspergillus kawachii culture grown on lemon pomace, the main one, exoPG1, was a glycosylated protein with a molecular mass of 75 kDa, isoelectric point in the 4.00-4.65 pH range, and a 3.0-4.0 pH optimum, though with activity at pH 2.0. ExoPG1 cleaved monomer units irrespective of the degree of substrate polymerization. Di-and trigalacturonic acids were completely hydrolyzed, whereas polygalacturonic acid (PGA) only incompletely. ExoPG1, along with a recombinant endoPG from the same fungal strain, was necessary for the hydrolysis of PGA down to the monomer. pH stability was maximum in the range 4.0-5.0 irrespective of the incubation temperature and decreased as the temperature increased from 30 to 70°C. The enzyme appeared not to require divalent cations for activity. Protein identification by MALDI-TOF-TOF MS/MS indicated homology of exoPG1 with the exopolygalacturonase PGXB of Aspergillus. niger, an exopolygalacturonase of Aspergillus tubingensis, and the exopolygalacturonase X of Aspergillus kawachii, a hypothetical enzyme predicted from the complete sequencing of the genome of the fungus. Both these latter proteins are unusual in that they have identical primary sequences. We therefore conclude that exoPG1 is probably the hypothetical A. kawachii exopolygalacturonase X. ExoPG2-having a molecular weight of 80 kDa, an isoelectricpoint between pHs 4.5 and 5.0, a 4.0 pH optimum, and kinetics with PGA similar to those of exoPG1-shared similarities with the exopolygalacturonase PGXC of A. niger and another proposed exopolygalacturonase of A.

The addition of tara and quebracho colorado tannins remarkably reduces the corrosion rate of aluminum in near‐neutral and naturally aerated NaCl solutions. The experimental results (potentiodynamic polarization curves, corrosion potential measurements, scanning electron microscopy–energy‐dispersive X‐ray spectroscopy [SEM‐EDS] analysis on exposed surfaces) show that both tannins behave as a mixed‐type corrosion inhibitor of aluminum. In the absence of tannins, the SEM‐EDS analysis of the exposed samples demonstrates the accumulation of corrosion products and the existence of chlorinated compounds adsorbed on the metal surface. In the samples immersed in both tannins solutions, a more homogenous and compact layer is formed over the aluminum surface. Furthermore, in these layers chlorine was not found, revealing a high blocking capacity of the chloride adsorption when the tannins are present. Taking into account these findings, an inhibitory mechanism of aluminum corrosion is proposed. This mechanism is interphase inhibition, which involves the adsorption and incorporation of tannin molecules during the corrosion products passive layer formation, resulting in a protective three‐dimensional structure that retards both anodic and cathodic reactions.

Purpose This paper aims to formulate and prepare a series of alkyd paints with new anticorrosive pigments, eco-friendly to the environment, based on a natural zeolitic rock modified by ion exchange to incorporate passivating cations. Design/methodology/approach The electrochemical characterization of the painted steel was carried out by conductivity measurements, linear polarization tests, measurements of the corrosion potential and electrochemical noise measurements. Besides, accelerated tests in standard environmental chambers were also carried out. Findings The results show that clinoptilolite–mordenite-based pigments incorporated in the paint provide acceptable anticorrosive properties, taking into account their low environmental impact and the use of a natural resource of low cost. The inhibitory efficiency of ZLa is higher than 80% and of ZPr is close to 70%. The electrochemical assays of the coated panels with the alkyd paints ZLa and ZPr shows similar behavior. Research limitations/implications In this work, good results were obtained with an alkyd resin, but other resins could be tested. Paints could also be formulated with modified zeolites as a complement to others traditional anticorrosive pigments. Practical implications These paints could be used for the protection of metal structures in low corrosive environments. Originality/value There are not many published works using zeolites as anticorrosive pigments.

RESUMEN Las hojas de las plantas perennes Rosmarinus officinalis, Laurus nobilis y Plectranthus coleoides presentan una gran cantidad de compuestos químicos que contienen heteroátomos en su estructura. Diversos estudios han reportado que este tipo de heterocompuestos presentan una gran afinidad química por las superficies metálicas. En este trabajo se presenta la obtención, caracterización y estudio del desempeño anticorrosivo sobre acero SAE 1010 de los extractos acuosos de las hojas de las plantas perennes antes mencionadas. Las especies vegetales fueron cultivadas y cosechadas en la zona del Gran La Plata, Provincia de Buenos Aires, República Argentina. La preparación de los extractos acuosos se realizó mediante la técnica de maceración. El residuo sólido de los extractos acuosos se caracterizó mediante espectroscopia infrarroja con transformada de Fourier (FTIR). La evaluación electroquímica se llevó a cabo mediante la exposición de muestras de acero SAE 1010 durante 24 h a un medio corrosivo en presencia de cada uno de los extractos, y el posterior análisis de las superficies obtenidas a través de microscopía electrónica de barrido (SEM) y espectroscopia de dispersión de rayos X (EDX). Los resultados fueron comparados con los obtenidos utilizando hidrato de polifosfato de zinc y aluminio (ZAPP), un pigmento anticorrosivo comercial. Los resultados obtenidos permiten concluir que los extractos de las tres especies vegetales inhiben la corrosión del acero SAE 1010 de manera comparable a la efectuada por ZAPP, siendo el extracto de Plectranthus coleoides el que presenta la mejor acción anticorrosiva.