The effect of TiO2 as a pigment in a polyurethane/polysiloxane hybrid coating/aluminum interface based on damage evolution

• Published in: Progress in organic coatings 2015-06, Vol.83, p.36-46
• Main Authors: Maya-Visuet, Enrique, Gao, Tongzhai, Soucek, Mark, Castaneda, Homero
• Format: Article
• Language: English
• Subjects: Aluminum; Coating; Corrosion damage evolution; Damage; Electrochemical impedance spectroscopy; Evolution; Exposure; Hybrid-coating system; Polyurethane/polysiloxane; Substrates; Titanium dioxide
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2015.02.001

•The pigment addition reinforces the paint by increasing the barrier properties.•The performance is influenced by the physical barrier of the coating, the TiO2 content is important for accumulating and distributing water more efficiently.•Of the systems tested, the system with 10wt% TiO2 provided the best corrosion inhibition.•The critical pigment volume concentration threshold is between 20wt% and 30wt%. The effect of titanium oxide as an additive on the performance of a polyurethane/polysiloxane hybrid coating was characterized by an electrochemical approach. The performance evolution was quantified by exposing the hybrid coating on an aluminum substrate to NaCl solution at pH 5 over time. Real-time measurements were performed to quantify and correlate the mechanisms that occur at the coating/substrate interface. Electrochemical impedance spectroscopy (EIS) quantified the hybrid coating/substrate interface performance over the course of the 263 days of exposure, and electrically passive elements described and characterized the degradation/performance stages upon exposure to the acidic NaCl solution. The addition of TiO2 produced hydrophobicity functionality, and TiO2 acted as a physical barrier layer that influenced the initial damage stage. Different exposure times were associated the different stages of damage evolution for the hybrid coating and coating/substrate interfaces. Electrochemical testing with high-resolution techniques such as AFM (atomic force microscope) and IFM (infinite focus microscope) characterized the coating surface and the interface performance and resolved the surface and defect formation observed with different levels of TiO2 content. Of the systems tested, the system with 10wt% TiO2 provided the best corrosion inhibition.