Morphology evolution and corrosion performance evaluation of the amorphous Ni-P coating prepared by picosecond LECD and modified by nanosecond laser remelting.

[Display omitted] • Laser remelting can remove surface cracks. • The remelted layer changes from amorphous to crystalline. • There are many pores in the remelted layer due to cracks. • The crack size affects the corrosion resistance of the remelted coating. The amorphous Ni-P coating crack may further propagate with an increase in electrodeposition (ECD) time, and hence decreases the corrosion resistance. In this study, the Ni-P coating was firstly prepared by picosecond (ps) laser-assisted ECD (LECD), followed by a nanosecond (ns) laser remelting step to remove cracks. The corrosion behavior was detailed evaluated under different LECD time and processing sequence. The results show that the ns laser remelting step results in an increase in surface roughness (Sa) by about one order of magnitude, as well as phase transition from amorphous to crystalline. The LECD time length significantly affect the corrosion behavior after the remelting step, as obvious decrease in corrosion resistance compared with the non-melted surface can be observed for 40 min and 90 min LECD. In contrast, for 180 min case, the corrosion behavior has been significant improved. Longer LECD time may reduce the surface corrosion defects on the remelted coating, and hence decrease the probability of solution-defect contact and hence cracks development, thus improving corrosion resistance. [ABSTRACT FROM AUTHOR]