| Due to the unique physical, chemical and mechanical characteristics of Ni-P deposits, such as the anticorrosive property, wear resistance, paramagnetic characteristic, high hardness and the electro-catalytic activity of hydrogen evolution, the Ni-P deposits had been used widely in various fields. But the particles of the Ni-P deposits were unregulated. So it was hard to avoid the pinholes in the deposits especially in brine mediums. Pit corrosion was the main reason why the electroless Ni-P deposits were limited to be used widely. The common method to enhance the pit corrosion resistance of Ni-P deposits was surface passivation in chromate solutions, but the Cr6+ was poisonous and had been limited to use in industry in many countries. So how to effectively enhance the pit corrosion resistance of the electroless Ni-P deposits in the condition of environmental conservation was the urgent affair.The corrosion resistance, especially the pit corrosion resistance of the single Ni-P deposit had been studied in the thesis. The annual average corrosion rate of the single Ni-P deposit in 5wt%NaCl solution was about 23.3μm/a, which was not high. To different thickness of the deposits, the time of the first rust on the deposit was different. When the thickness of the Ni-P deposit was 30μm, after 36h the first rust had appeared on the Ni-P deposit, which indicated that the pit corrosion resistance of the single Ni-P deposit was poor. The difference of the open circle potential of the Ni-P deposit and that of the steel was about 250mV, which indicated that the Ni-P deposit was cathodic to the steel. There was passive film on the single Ni-P deposit with the time immersed in 3.5wt%NaCl solution increasing. The passivation region could be seen on the polarization curves and the time constant of the passive film also could be seen from the EIS curves. But with the immersed time increasing, the corroded current increased in the region of the...
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