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

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(NO3)(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.