Formulation and Assessment of a Wash-Primer Containing Lanthanum “Tannate” for Steel Temporary Protection

Abstract

Tannins are polyphenols synthesized by plants and useful for the coating industry as corrosion inhibitors. In addition, lanthanum salts have a great inhibitory effect on steel corrosion. The aim of this study was to obtain lanthanum ''tannate'' with adequate solubility to be incorporated as the corrosion inhibitor in a wash-primer. The ''tannate'' was obtained from commercial ''Quebracho'' tannin and 0.1 M La(NO 3 ) 3 . The soluble tannin was determined by the Folin-Denis reagent, while the concentration of Lanthanum was obtained by a gravimetric procedure. The protective action of ''tannate'' on SAE 1010 steel was evaluated by linear polarization curves and corrosion potential measurements. Lanthanum ''tannate'' was incorporated in a wash-primer formulation and tested by corrosion potential and ionic resistance measurements. The corrosion rate was also determined by the polarization resistance technique. Besides, the primer was incorporated in an alkyd paint system and its anticorrosion performance assessed in the salt spray cabinet and by electrochemical impedance spectroscopy. Results showed that lanthanum ''tannate'' primer inhibits the development of deleterious iron oxyhydroxides on the steel substrate and incorporated into a paint system had a similar behavior to the primer formulated with zinc tetroxychromate.

A Novel Environmentally Friendly Synergistic Mixture for Steel Corrosion Inhibition in 0.51 M NaCl

“…Additionally, metal cations in high oxidation state, such as ferric ions dissolved from the steel surface into the electrolyte, are hard Lewis bases, so that formation of protective deposits of hardly soluble complexes and/or chelates of ferric ions with anionic organic ligands is possible. 8 Components of the inhibitor mixture investigated in the present study were chosen after careful consideration of their environmental friendliness and previously published characteristics relevant to corrosion inhibition. E.g., ethanolic propolis extract applied to mild steel forms a very effective anticorrosion coating in neutral and near neutral aqueous 3.5% w/v NaCl solution.…”

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

“…In previous research, the precipitation of tara or red quebracho (Schinopsis lorentzii) tannins with a lanthanum salt was carried out [20,21]. The protective action of these lanthanum "tannates" was corroborated and it has two contributions.…”

“…Tannins solutions were prepared from the commercial powders of tara (T40, INDUNOR) and quebracho (UNITAN CROWN ATO) tannins [20,21]. The powders were extracted for 1 h with distilled water at 90°C.…”

“…The extracts were vacuum filtered. KNO 3 1 M was employed to coagulate colloidal particles in the quebracho extract [21].…”

“…In order to prepare lanthanum "tannates", the extracts were put in contact with La(NO 3 ) 3 0.1 M and the pH adjusted to 8.0 with NaOH 1 M, under constant stirring for 1 h [20,21]. The precipitated obtained was washed with distilled water and dried at 100°C for 24 h.…”