A novel electrodeposited nanostructured Ni coating with grain size gradient distribution

A grain size gradient (GSG) nanostructured (NS) Ni coating on steel sheet was prepared by gradually increasing the grain refiner (saccharin) concentration during direct-current electrodeposition. The X-ray diffractometer (XRD) analysis indicated that preferred orientation of the deposit changes to (111) from (200) crystal orientation with increasing the saccharin concentration. The grain size varies from 22 nm on surface to about 586 nm near the coating–substrate interface observed by transmission electron microscopy. Hardness, electrochemical measurement in NaCl solution and bend test revealed that the GSG NS Ni coating shows high hardness, more noble corrosion resistance properties as well as excellent adhesion to substrate compared with the uniform grain size NS Ni coating on the same substrate.