How is the corrosion resistance of nickel-phosphorous electroless nickel?
Often excellent, often better than metallic nickel. Since the amorphous condition is free from grain boundaries, a whole range of corrosion sensitive situations is eliminated. The surface passivates much the same as nickel. In galvanic corrosion these coatings have the same electropotential as nickel and generally behave much the same as metallic nickel. How do nickel-boron electroless nickel coatings behave? As deposited, the hardness is high and with heat treating, the hardness can approach hard chromium. The wear resistance can be excellent. However, corrosion resistance is not as good as a nickel-phosphorous coating since the nickel-boron coating is not wholly amorphous. The residual coating stress is generally tensile, with the amount of tension depending on the chemistry of the bath. The strength and ductility of the nickel-boron coatings are only about 1/5 that of the nickel-phosphorous coatings. Compared to electroplated nickel, why does electroless nickel tend to be so hard an
