Abstract
Corrosion fatigue strength of electroless Ni-P steel was investigated by rotating bending fatigue test at 0.6 and 60Hz in dropping 3% NaCl solution. The changes of microstructure of Ni-P film by cyclic stressing were examined by X-ray technique. 1. Ni-P film keeps amorphous structure and exhibits an excellent corrosion resistance regardless of the presence of applied stress. 2. Since a pre-microcrystalline forms in Ni-P film by cyclic stressing, the corrosion resistance decreases, accopmanied by negative shift of the corrosion potential. 3. The corrosion resistance of the plated layer decreases with increasing the number of cyclic stressings or local crystallization. Then corrosion pits were produced on the surface, stress concentration is induced at the bottom of pit and then the pit grows up to corrosion fatigue crack. 4. The corrosion fatigue life of steel was improved by about 50 percent by Ni-P plating, which is not as much as was expected for the amorphous metal.
