Formulation and assessment of a wash-primer containing lanthanum "tannate" for steel temporary protection

ORIANA D'ALESSANDRO; GONZALO SELMI; CECILIA DEYÁ; ALEJANDRO DI SARLI; ROBERTO ROMAGNOLI

JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE

SPRINGER

Año: 2017

1059-9495

Tannins are polyphenols synthesized by plants and incorporated in the coating industry as corrosion inhibitors. On the other hand, lanthanum solutions have a great inhibitory effect over steel corrosion.The aim of this study was to obtain lanthanum "tannate" with low solubility in order to be incorporated as corrosion inhibitor in a wash primer.The "tannate" was obtained with commercial Tara (Caesalpinia spinosa) tannin and 0.1M La(NO3)3. The soluble tannin was determined by the Folin-Denis reagent while the concentration of La in the saturated solution was obtained by a gravimetric procedure. The protective action of "tanate" on SAE 1010 steel was evaluated by lineal polarization curves and corrosion potential measurements. Lanthanum "tannate" was incorporated in a wash primer formulation and tested by corrosion potential and ionic resistances measurements; the corrosion rate was determined by the polarization resistance technique. Besides, the primer was incorporated in an alkyd paint system and tested in the salt spray cabinet and by electrochemical impedance spectroscopy. Results showed that lanthanum ?tanate? primer inhibit the development of globular iron oxyhidroxides on the steel substrate and, incorporated in a paint system, outperformed, in the salt spray test, the primer formulated with zinc tetroxychromate.