Formulation and Testing of a Waterborne Primer Containing Chestnut Tannin

By O.R. Pardini, J.I. Amalvy, A.R. Di Sarli, R. Romagnoli, V.F. Vetere

The development of a water-based pretreatment system containing chestnut tannin and phosphoric acid and the assessment of its anticorrosive properties through different conventional tests are discussed in this work. Treated steel panels coated with different paint systems were subjected to standardized (salt spray, humidity chamber, adhesion, and flexibility) and electrochemical (corrosion potential, EIS) tests.

Electrochemical tests were performed by employing only panels coated with the wash primer to determine its protective effect. The binder employed in this re-search was prepared in the laboratory by emulsion polymerization of acrylic monomers. It was found that the tested formulation protected steel against corrosion by forming ferric tannate, which prevented oxide formation.

After performing the salt spray tests, it was observed that no oxide spots developed on the scratch mark, although some blisters were detected. The good stability of the binder in low pH media (pH: 2.0-2.5) and the binder/substrate interaction are decisive factors in the performance of this aqueous pretreatment system.