Recycling of photocatalysis-reduced Cr(VI) in metal surface passivation protection

The hexavalent chromium waste solution after photocatalysis treatment was reused for surface passivation of low carbon steel (sample p-HCC ), to improve its corrosion resistance. The structure and the anticorrosion properties of p-HCC were confirmed by SEM, XPS, electrochemical impedance spectroscopy. Compared with passivation samples treated by pure Cr(III) solution (sample TCC ), the polarization resistance of p-HCC film (2994 Ω cm 2 ) was larger than that of TCC (2043 Ω cm 2 ), which may be due to the higher Cr content in p-HCC film ( p-HCC : 0.71 atom%, TCC : 0.13 atom%), which was caused by a better interaction between Fe ions and Cr-compound due to Cr(VI) residue and photocatalyst in the photocatalysis reduction for hexavalent chromium. Graphical abstract