Crystal Structure and Chemical State of Surface of Electrodeposited Zn-Fe-Cr Alloy Coating

The crystal structure and chemical state of the surface of electrodeposited Zn-Fe-Cr coating were investigated by X-ray diffraction and XPS. The X-ray diffraction patterns of Zn-Fe-Cr deposits with different compositions indicated that the crystal structure of electrodeposited Zn-Fe-Cr coating was almost the same as that of electrodeposited Zn-Fe coating. The X-ray photoelectron spectra of the Zn-Fe-Cr deposit with 70.3 mass% Fe -6.5 mass% Cr obtained after Ar sputtering showed that the surface layer of the deposit consists of oxide or hydroxide, while the ratio of metallic elements gradually increased inside of the surface layer. This interesting structural feature of electrodeposited Zn-Fe-Cr coating can be explained by the deposition mechanism such as a hydroxide suppression mechanism and an induced co-deposition by iron-group metals proposed previously.