Preparation Of Anticorrosion Coatings Based Modified Polyurethane And The Research With Anticorrosion Performance

Waterborne polyurethane is becoming a research focus of materials owning to its environmental friendly performance and good properties. However water resistance of waterborne polyurethane is poor, and its application is limited. This paper aims to graft and modify waterborne polyurethane, and improve its water resistance, then used to prepare zinc-rich coatings and study its anticorrosion performance.In this paper, waterborne polyurethane were modified by biological resource castor oil and silane coupling agent KH550(H2NCH2CH2Si(OC2H5)3) as materials respectively. Infrared of emulsion confirmed the effective graft of modifiers. We have studied the effects of n(NCO):n(OH), dimethylol propanoic acid(DMPA),trimethylolpropane(TMP) and epoxy resin E-44 about the properties of waterborne polyurethane emulsion and films, and focusly inspected the consumption of castor oil and KH550 on mechanical properties and water resistance of films.Then the two modified waterborne polyurethane were used to prepare zinc-rich coatings with different amounts of zinc powder respectively. Modified waterborne polyurethane zinc-rich coatings were characterized by linear sweep voltammetry testing, corrosion potential test, electrochemical impedance spectroscopy(EIS), X-ray diffraction(XRD) and scanning electron microscopy and spectroscopy(SEM-EDS). The electrochemical behavior of the zinc-rich coatings were investigated in 3% NaCl electrolyte. Meanwhile, the anticorrosion of the zinc-rich coatings with a small amount of aluminum powder were studied.The results showed that the instruction of castor oil and KH550 increased the crosslinking degree of waterborne polyurethane system, improved the water resistance of waterborne polyurethane films, made their water absorption declined, and got the waterborne polyurethane emulsion with excellent properties. Zinc-rich coatings were prepared with modified waterborne polyurethane. Corrosion behaviors of the modified waterborne polyurethane zinc-rich coatings and unmodified waterborne polyurethane zinc-rich coatings were researched by electrochemical methods and surface observation test. The increasement of zinc powder could raise the impedance value of the coatings accordingly, and in the immersion process, the coating with higher zinc powder content had a longer cathodic protection duration and good anticorrosion performance. Compared with unmodified waterborne polyurethane zinc-rich coatings, castor oil modified waterborne polyurethane zinc-rich coatings had excellent anticorrosion. Moreover, the introduction of a small amount of aluminum powder contributed to increasing the barrier effect and improving the anticorrosion performance of the coatings.