Corrosion, erosion and erosion-corrosion behavior of SiC reinforced Ni-P coating on the surface of X65 steel

In the present paper, corrosion, erosion and erosion-corrosion behavior of Ni-P-SiC composite coatings on the surface of X65 carbon steel were investigated. The coatings were produced in an electroless solution containing 0, 5, 10, and 15 g/l SiC particles. The prepared coatings were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD) and microhardness measurements. Polarization tests in a stagnant solution and during erosion-corrosion were also performed to characterize the corrosion behavior of various coatings. Erosion-corrosion and pure erosion tests were carried out using a slurry impingement rig at an impingement angle of 90° under a jet velocity of 6.5 m/s and the synergy parameters were then calculated. SEM images and XRD results showed an increase in the amount of embedded SiC particles in the coatings by increasing the concentration of SiC particles in Ni-P bath up to 10 g/l. Further increase in the SiC concentration in the electroless bath had less effect on the amount of embedded SiC in the coatings. Polarization tests during erosion-corrosion revealed that the embedded SiC particles could largely lower the corrosion rate of the composite coatings as compared with Ni-P coating.  The results also showed that the addition of SiC particles in the coating resulted in a significant decrease in the erosion and erosion-corrosion rates. This was attributed to the limited plastic deformation on the surface of the composite coating as a result of the presence of SiC particles.