The influence of two types of nano-structured Ni-P and zinc-phosphate primer on the corrosion resistance of painted low carbon steel

One of the important parameters to increase the corrosion resistance of base metal is the selection of an appropriate primer. This is an important factor for increasing the adhesion and durability of the coating. In this study, the effect of two different primers on the corrosion resistance of the painted low carbon steel has been investigated. For this purpose, zinc phosphate (which is normally used as a paint primer) and Ni-P nano-structured coating were used. The corrosion resistance was evaluated by potentiodynamic and cyclic polarization tests, electrochemical impedance spectroscopy and salt spray tests. The Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) were used to characterize the morphology and composition of the coatings. And adhesion of the paint was investigated by pull off test. The results showed that the corrosion resistance of the painted low carbon steel with Ni-P nano-structured primer was more than that of the zinc phosphate primer. So that the polarization resistance increased by about 79.1 kΩ.cm2 and the pitting potential increased to 0.49V for nano-structured coating samples compared to zinc phosphate samples. Also, the results of the paint adhesion test indicated a high adhesion to nano-nickel-phosphorus primer compared to the phosphate-zinc primer.