Barrier and adhesion properties of anti-corrosion coatings based on surfactant-free latexes from anhydride-containing polymers

We have successfully obtained surfactant-free latexes from anhydride-containing polymers, including poly(styrene-alt-maleic anhydride) (PSMA), maleinized polybutadiene (PBDMA), and poly(octadecene-alt-maleic anhydride) (POMA). Here we report barrier and adhesion properties of the coatings made from these surfactant-free latexes, which were crosslinked with adipic acid dihydrazide (ADH). The barrier property of these coatings was studied with electrochemical impedance spectroscopy in NaCl solutions on pretreated aluminum substrates. PSMA and PBDMA-based coatings demonstrated good barrier property, indicated by the absence of corrosion after 1-month immersion in NaCl solutions, which was comparable to that of a commercially available polyester coating. The polyester coating, however, was found to hydrolytically degrade when immersed in a NaCl solution, which was not observed for our latex-based coatings. The POMA-based coating showed inferior barrier property on un-pretreated aluminum, likely due to inhomogeneous film formation and poor adhesion to the substrate, but the adhesion could be improved by an alkali pretreatment of the substrate. In comparison, PBDMA and PSMA-based coatings showed much better adhesion toward the aluminum substrates. The anti-corrosion behavior appeared to be closely related to both the barrier and adhesion properties of the coatings on the metal substrate.