Magnesium salts can enhance corrosion-protective properties of organic coatings. Here, mirocrystalline magnesium thiodipropionate (MgTDPA) and amorphous magnesium acetate thiodipropionate (MgAcTDPA) are synthesized in water via replacement and metathesis reactions, respectively, from 3,3′-thiodipropionic acid (TDPA), a nontoxic, film-forming dicarboxylic acid. The ability of the uncovered magnesium thiodipropionates to accelerate ring-opening polymerization of benzoxazines such as the aniline derivative of bisphenol and curing of the epoxy resin-amine hardener is confirmed using differential scanning calorimetry and rheological methods. The corrosion inhibition of galvanized steel by magnesium thiodipropionates was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy measurements. Adsorption of TDPA anions on the galvanized steel surface followed the Langmuir adsorption isotherm. Epoxy-amine powder compositions containing MgTDPA were designed and coated on galvanized steel by electrodeposition, and performance of magnesium thiodipropionate as a delamination inhibitor was investigated by immersion and salt-spray cyclical tests. The widening of cuts in the coating (scribe creep) results demonstrated the dramatic protective action of magnesium thiodipropionate in the epoxy-amine powder coatings. Magnesium thiodipropionates appear to be economical and functional additives to organic coatings, aiding in curing and corrosion protection.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering