Effect of Heat Treatment and Passivation on Corrosion Behavior of Electroless Ni-P Coating on 20# Steel in Simulated Soil Solution

Ni-P coating was prepared on 20# steel by electroless deposition. And then, the Ni-P coating was treated by heat treatment and passivation sequentially to greatly improve its corrosion resistance in simulated soil solution. The corrosion resistance was evaluated by potentiodynamic polarization curves and immersing testing. The results show that, the corrosion rate and corrosion current density of the Ni-P coating treated by heat treatment and passivation is 0.12 g/(cm 2 ·d) and 2.49×10 -6 A/cm 2 respectively after immersing in simulated soil solution for 16 days, showing excellent corrosion resistance. However, the corrosion rate and corrosion current density of 20# steel is 1.73 g/(cm 2 ·d) and 2.06×10 -4 A/cm 2 respectively after immersing in simulated soil solution for 16 days, indicating poor corrosion resistance. Ni-P coating itself has good corrosion resistance, and it presents excellent corrosion resistance after heat treatment and passivation, which is beneficial to protect 20# steel in simulated soil solution.