Modified potassium titanate whiskers for preparation of enhanced corrosion-resistant phosphating conversion coatings with high NIR reflectivity on mild steel

Abstract

In this paper, Potassium titanate whiskers (PTW), a kind of high NIR reflectional material, were modified with stearic acid (SA) and used as a green accelerator in phosphating bath to build super-hydrophobic phosphating conversion coatings (PCCs) with enhanced corrosion resistance and high NIR reflectivity on mild steel in one-step at low temperature. The scanning electron microscopes (SEM), water contact angle (WCA), X-ray diffraction (XRD), potentiodynamic polarization, copper sulfate titration, electrochemical impedance spectroscopy (EIS), long-term immersion test, NIR reflectivity, linear abrasion experiment as well as tape peeling experiment were investigated to explore the performance of PCCs. The PCCs with the optimal 0.8 g/L concentration of SA-PTW possesses the densest structure, the largest WCA of 153° and the highest NIR reflectivity of 48 %. The potentiodynamic polarization results show that the 0.8-SA-PTW occupies the lowest corrosion rate (7.531 ×10−4 mpy), and remains minimal (3.56 ×10−3 mpy) after soaking in 3.5 wt % NaCl solutions for 20 days, resulting in enhanced long-term corrosion protection of mild steel. These special properties of PCCs effectively prevent the invasion of corrosive medium and the heat accumulation which would have great potential applications in anti-corrosion “cool coatings” for exterior corrosion protection of body and hull.