A new amorphous alloy deposit with high corrosion resistance

The corrosion behavior of electrodeposited Ni-P, Ni-W, Ni-W-P, and Fe-W alloys was tested, and the effects of the additive elements W and P on the corrosion resistance of amorphous deposits were studied. Corroson rates of the alloys were compared to those of stainless steel. Results showed the W content in electrodeposited NL-W-P amorphous alloy was as high as 55.2 wt%. The hardness (Vickers [HV]) of the alloy was from 700 HV to 800 HV and 1,300 HV to 1,400 HV after heat treatment at 550 degrees C. The hardness, wear resistance, and corrosion resistance of the deposit were shown to be superior to those of NL-P amorphous deposit.(1) The corrosion potential (E(corr)) was moved to noble by adding P to the deposit, and the passive current density (i(pass)) dropped remarkably with the addition of W. Amorphous Ni-W, Ni-W-P, and Fe-W alloy deposits showed high corrosion resistance in acid solutions. Immersion tests in 1 mol/L (4.54 mol/gal) hydrochloric acid (HCl) solution at 30 degrees C showed the corrosion rate of type 304 stainless steel (UNS S30400) was 10 times that of Ni-W-P amorphous deposit, 40 times that of Ni-W amorphous deposit, and 15 to 20 times that of Fe-W amorphous deposit. In 0.5 mol/L (2.27 mol/gal) sulfuric acid (H2SO4) solution at 30 degrees C, the corrosion resistance of the amorphous deposit was poorer than that of type 304 SS, but at 60 degrees C, the corrosion rate of type 304 SS increased dramatically, to similar to 180 times that of Fe-W amorphous deposit and 100 to 700 times that of the Ni-based amorphous deposit.