In-situ phosphatization and enhanced corrosion properties of films made of phosphate functionalized nanoparticles

Abstract

In the present work a thin, stand-alone waterborne coating with excellent anticorrosion performance was successfully designed thanks to a built-in ability to in-situ phosphatize low carbon steel substrates. During film formation, the phosphate functionalities, incorporated by using a phosphate functional surfmer, were able to interact with steel leading to a thin iron phosphate passive layer at the coating-metal interface, as proven by SEM-EDX, FTIR and XPS. The phosphatization layer that plays a key role on the excellent anticorrosion properties obtained (measured by EIS analysis of coated sample immersed in 3.5 wt% NaCl solution and in an aggressive salt spray chamber), strongly depends on the humidity at which the waterborne dispersion is applied; at relative humidity above 60%, optimum performance is achieved.