Enhanced corrosion resistance of discontinuous anodic film on in situ TiB2p/A356 composite by cerium electrolysis treatment

The agglomerates of TiB2 particulates and Si phases badly break the continuity of anodized film of in situ TiB2p/A356 composite, which will restrict the improvement of corrosion resistance. In this study, cerium conversion coatings were successfully deposited on anodized TiB2p/A356 composite by electrolysis treatment. Scanning electron microscope observations show that the conversion coatings effectively cover the whole surface of anodized composite. The conversion coatings on continuous porous anodic film are composed of many spherical nano-particulates; however, at the regions without anodic film the conversion coatings present a planar structure. The different morphologies are attributed to the different formation characteristics of cerium conversion coatings at different regions of anodized composite. X-ray photoelectron spectroscopy analysis indicates that the conversion coatings consist of CeO2, Ce2O3, Ce(OH)(4), and Ce(OH)(3). The potentiodynamic polarization results testify that the integrated surface coatings of anodic film and cerium conversion coating provide a higher degree of protection for in situ TiB2p/A356 composite in a chloride-containing environment.