Primers based on tara and quebracho tannins for poorly prepared steel surfaces

Abstract

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.

Tannins as interphase corrosion inhibitors for aluminum in near‐neutral chloride solutions

“…The most employed ones were “quebracho colorado” ( Schinopsis balansae/lorentzii ), [ 8,9 ] mangrove ( Rhizophora apiculata ), [ 10,11 ] mimosa (black wattle tree, Acacia mearnsii ), [ 12,13 ] radiata pine ( Pinus radiata ), [ 14 ] chestnut ( Castanea sativa ), [ 15 ] and tara ( Caesalpinia spinosa ). [ 16,17 ]…”

“…The most employed ones were "quebracho colorado" (Schinopsis balansae/lorentzii), [8,9] mangrove (Rhizophora apiculata), [10,11] mimosa (black wattle tree, Acacia mearnsii), [12,13] radiata pine (Pinus radiata), [14] chestnut (Castanea sativa), [15] and tara (Caesalpinia spinosa). [16,17] In acid solutions, the corrosion inhibition mechanism is often related to the specific adsorption of the tannin molecules on the aluminum surface, with the formation of a compact and stable two-dimensional (2D) layer that isolates the metal from the corrosive environment (interface inhibition). However, in near-neutral media, the anticorrosive action of tannins over aluminum may be explained by the concept of interphase inhibition.…”

Protección anticorrosiva de un convertidor de óxido natural (Mimosa tenuiflora) aplicado sobre productos de corrosión de un acero AISI 1018

“…Si hay ausencia de oxígeno debajo de esta capa, su concentración es limitada, se forma un óxido oscuro compuesto de magnetita (Fe3O4), la cual no suele ser protectora, ya que en su presencia la corrosión del acero puede acelerarse mediante un efecto de acoplamiento galvánico entre el sustrato de acero y el óxido. En realidad, la formación de una capa de óxido compacta, altamente adhesiva y por lo tanto protectora sobre la estructura de acero no es común (Zhao et al, 2014), y pueden dificultar la aplicación de pinturas y por tanto, su rendimiento, pues genera una mala adherencia al sustrato metálico (Byrne et al, 2019). La protección y prevención contra la corrosión son muy importantes, ya que una parte considerable del producto nacional bruto de las naciones se invierte anualmente en acciones para evitar la corrosión.…”

“…ISSN 2007 -0705, pp. : 1 -22 -6 -temperatura, el disolvente, el tamaño de las partículas y de los procedimientos de extracción, que resultan específicos para diferentes especies de plantas (Byrne et al, 2019).…”

Study of the anticorrosive properties of “quebracho colorado” extract and its use in a primer for aluminum1050

“…Tannins can retard the corrosion reactions of metals by adsorbing on their surfaces through the electron rich oxygen atoms in their structures [14], so the application of tannins in corrosion studies has been widely investigated [15]. Most corrosion researches of tannins involve their anticorrosive properties on steel [16] or as rust converters [17][18][19]. Some researchers worked on tannin solution [20][21][22][23][24] or with natural extracts containing tannins [25] or in anticorrosive primers [17,21,[26][27][28][29][30] and paints [28,31] to protect steel.…”